Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry

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Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry for the Alcohols, Hydroperoxides, Vinylic, Alkoxy and Alkylperoxy Radicals Suriyakit Yommee, and Joseph William Bozzelli J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.5b09004 • Publication Date (Web): 04 Jan 2016 Downloaded from http://pubs.acs.org on January 10, 2016

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The Journal of Physical Chemistry

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Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry for the Alcohols, Hydroperoxides, Vinylic, Alkoxy and Alkylperoxy Radicals

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Suriyakit Yommee and Joseph W. Bozzelli* Department of Chemistry and Environmental Science, New Jersey Institute of Technology

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University Heights, Newark, NJ 07102 USA

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Abstract: Cyclopentadienone has one carbonyl and two olefin groups resulting in 4n + 2 pi electrons in a cyclic five member ring structure. Thermochemical and kinetic parameters for the initial reactions of cyclopentadienone radicals with O2 and the thermochemical properties for cyclopentadienone - hydroperoxides, alcohols, alkenyl , alkoxy and peroxy radicals were determined by use of computational chemistry. The CBS-QB3 composite and B3LYP density function theory methods were used to determine the enthalpies of formation (∆fHo298) using the isodesmic reaction schemes with several work reactions for each species. Entropy and heat capacity, So (T) and CPo(T) (50 K ≤ T ≤ 5000 K) are determined using geometric parameters, internal rotor potentials, and frequencies from B3LYP/6-31G (d,p) calculations. Standard enthalpies of formation are reported for parent molecules as cyclopentadienone, and cyclopentadienone with alcohol, and hydroperoxide substituents, and for the cyclopentadienone-yl vinylic, alkoxy, and peroxy radicals corresponding to loss of a hydrogen atom from the carbon and oxygen sites. Entropy and heat capacity vs. temperature also are reported for the parent molecules and for radicals. The thermochemical analysis shows The R• + O2 well depths are deep, on the order of 50 kcal mol-1 and the R. + O2 reactions to RO + O (chain branching products) for cyclopentadienone-2-yl and cyclopentadienone-3-yl have unusually low reaction (∆Hrxn) enthalpies, some 20 or so kcal/mol below the entrance channels. Chemical activation kinetics using quantum RRK analysis for k(E) and master equation for fall-off are used to show that significance of chain branching as a function of temperature and pressure can occur when these vinylic radicals are formed.

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of the ring radical sites appear to undergo chain branching to a more significant extent than the vinyl or

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phenyl radical1-2. Evaluation of the bond dissociation energies (BDEs) in the alcohol and hydroperoxy

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groups on the ring carbons, in this study, shows the strong effect that the carbonyl group has on bonding in

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these electronegative oxygen groups and on the overall bond energies on the ring, as compared to benzene.

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This data is important in understanding the reactions and stability of cyclopentadienone under thermal and

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combustion conditions. To our knowledge no one has studied the extensive thermochemistry or kinetics of

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these oxygenated derivatives and corresponding radicals.

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Several studies on the thermal decomposition of methoxy and dimethoxy benzenes, methoxy phenols, and di-

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phenols have shown that cyclopentadienone is an important intermediate.3-6 Cyclopentadienone (C5H4O) has

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also been considered an oxidation product of cyclopentadiene (C5H6), and a decomposition product of mono

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aromatics and benzoquinones; however experimental oxidation studies have been inconclusive as to

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formation of cyclopentadienone as a stable intermediate from reactions of cyclopentadiene.2, 7

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Key words cyclopentadienone, peroxides, alcohols, bond energies, oxidation kinetics, chain branching

Introduction Cyclopentadienone has a 4n + 2 pi electron configuration similar to that of benzene and furans and reactions

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ACS Paragon Plus Environment


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Da Costa et al.1 reported that cyclopentadienone is one of the main products from the thermal decomposition

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of benzoquinone (C6H4O2) as a result of CO elimination, where it further reacts to unsaturated non-cyclic

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products of acetylene and vinylacetylene 5. Alzueta et al8 have constructed a detail kinetic reaction model of

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benzene oxidation forming cyclopentadienone (C5H4O) as a major product but they needed rapid

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dimerization and radical addition reactions to convert their calculated cyclopentadienone intermediate to new

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products, in order to describe its lack of buildup and observation in their experimental results.

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Schraa et al 9 et al reported results from thermal decomposition of two cyclopentadienone precursors,

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orthobenzoquinone, and dihydro-benzodioxin. They proposed that cyclopentadienone was formed, but not

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observed due to rapid consumption at temperatures between 850-1100 K and low radical concentrations.

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They suggested that it was lost to a fast dimerization product with a reaction rate of 4.0*1011 cm3 mol-1s-1 at

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850 K via observation the cyclopentadienone dimer. Dejong et al10 and studied thermal reactions of

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phenylene sulfite which was indicated to decompose to form cyclopentadienone. They also reported the

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need for rapid conversion or dimerization of the initially formed cyclopentadienone to explain the formation

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of the observed product dimer.

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Butler and Glassman7 conducted experiments to investigate the formation of cyclopentadienone from

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oxidation studies of cyclopentadiene between 1100 to 1200 K. They considered that the cyclopentadienone

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would be a significant intermediate in C5 ring oxidation processes under combustion conditions; but it was

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not detected under their high temperature oxidation conditions.

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Because of the lack of observation of cyclopentadienone in the Butler and Glassman experiments, Wang and

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Brezinsky2 used computational chemistry to study its stability via unimolecular decomposition to the

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formation of cyclobutadiene (C4H4) via elimination of CO. They reported a several step mechanism with

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overall barrier of 59 kcal mol-1 for this product set.

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Cyclopentadienones are considered important products in the thermal oxidation of aromatic species (Sebbar

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et al11) where a phenyl radical reacts with O2 to form a peroxy radical and the peroxy radical further reacts to

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insert an oxygen atom into the ring, forming a seven member cyclic radical. This seven member cyclic

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radical undergoes ring opening and then a ring closing to form a new 5 member ring - 2-formyl-

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cyclopentadienone -3-yl radical , which loses the HC•O group to form cyclopentadienone. The intermediate

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was identified by work of Kirk et al12 in their experiment with photo ionization detection of benzene

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oxidation products. As noted above, unimolecular dissociation reaction of cyclopentadienone involves loss

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CO to form cyclobutadiene with a barrier of 59 kcal mol-1 or formation of two acetylenes plus CO13, where

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the reaction is 78 kcal mol-1 endothermic.

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In 2014, Ormond et al14 used flash pyrolysis of o-phenylene sulfite (C6H4O2SO) to provide a molecular beam

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of cyclopentadienone with collection for identification by matrix isolation. They confirmed products via

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photo-ionization mass spectroscopy (PIMS) and infrared spectra of cyclopentadienone. They also reported

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infrared frequencies, which were validated with calculations. Ormand et. Al.15 further studied

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cyclopentadienone unimolecular decomposition in a fast flow thermal micro reactor identifying two major

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sets of products (i.) vinyl acetylene and (ii) two acetylenes, both sets with CO. Scheer et al5 reported that

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cyclopentadienone is detected and confirmed by IR spectroscopy as an intermediate in a unimolecular

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decomposition of methoxyphenols.

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Sirjean et al16 used theoretical chemistry to evaluate pathways leading to cyclopentadienone with both

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Density Function Theory (DFT) methods and Coupled Cluster Theory. They reported the thermal deposition

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pathways leading to cyclopentadienone from phenylperoxy radical, similar to that of Sebbar et al11. Battin-

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Leclerc reported that the kinetics and thermochemistry of cyclopentadienone (C5H4O), along with its peroxy

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radicals and alkoxy aromatic group needed to be investigated in order to have a full understanding of the

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chemistry for C5 oxygenated compounds17.

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In an early study Zhong and Bozzelli18 calculated the thermochemistry of cyclopentadienone and its radicals

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using known values of similar reactants, intermediates, and product species from the literature and group

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additivity contributions with available hydrogen bond increments; they estimated ∆fHo298 of

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cyclopentadienone at 7.4 kcal mol-1. The ∆fHo298 of cyclopentadienone was subsequently calculated by Wang

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and Brezinsky1 at 13.2 kcal mol-1 using ab initio molecular orbital calculations at the G2(MP2,SVP) and

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G2(B3LYP/MP2,SVP) levels of theory and with the use of isodesmic reactions. In a separate study the heat

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of formation data of cyclopentadienone (12.75 kcal mol-1) was calculated by Robinson and Lindstedt in

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201119, where the kinetic and thermochemical parameters were calculated using G4/G4MP2 and G3B3

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composite methods. Linstedt also determined the thermochemical data relevant to the oxidation reactions of

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the cyclopentadiene and oxygenated cyclopentadienyl intermediates using B3LYP with the 6-31G (2df,p)

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basis set.

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Under combustion conditions, cyclopentadienone can react to form radicals from loss (abstraction) of the

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ring hydrogen atoms, and the formed alken-yl radicals will react with O2 to form peroxy and alkoxy radicals

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at the different sites on the ring. These alkenyl radicals can also undergo unimolecular beta scission 3



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reactions leading to ring opening and formation of reactive, unsaturated non-cyclic species; these are

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illustrated below.

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Thermochemical properties: formation enthalpies (∆fHo298), entropies (So), heat capacities (CPo(T)), and bond

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dissociation enthalpies (BDEs) for the vinylic carbon radicals, hydroperoxides, peroxy radicals, alcohols and

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alkoxy radicals of cyclopentadienone are needed to understand reaction paths and to assist in developing the

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chemical kinetic mechanisms. Ab initio composite and Density Functional Theory methods were used with

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work reactions to calculate the thermochemical properties for the target parent molecules, the different

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radical intermediates and for the transition state structures needed for kinetic parameters.

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COMPUTATIONAL METHODS

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of H atoms, plus standard enthalpies of formation for the parents and radicals have been calculated using

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B3LYP hybrid density functional theory in conjunction with the 6-31G(d,p)20-21 basis set and the composite

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CBS-QB3 level of theory22. The B3LYP method combines the three-parameter Becke exchange functional,

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B3, with Lee-Yang-Parr correlation functional as LYP. CBS-QB3 is a multilevel model chemistry that

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combines the results of several ab initio and density functional theory (DFT) individual methods and

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empirical correction terms to predict molecular energies with high accuracy and reasonably low

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computational cost. All quantum chemical calculations have been performed within the Gaussian 03 suite of

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programs23.

The structures of cyclopentadienone and alcohols and hydroperoxides, the radicals corresponding to the loss

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Standard Enthalpies of formation (∆fHo298) are evaluated using calculated energies, zero point vibration

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energy (ZPVE), plus thermal contributions (to 298K) at the B3LYP/6-31 g(d,p) and CBS-QB3 levels of

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theory and use of work reactions24-25. The calculated total energy at B3LYP/6-31 g(d,p) is corrected by the

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ZPVE, which is scale by 0.9806 , as recommended by Scott and Radom26. The CBS-QB3 uses geometry

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from B3LYP/CBSB7 calculations. To more accurately evaluate the standard enthalpy of formation (∆fHo298),

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a number of homodesmic and isodesmic work reactions have been used to calculate the standard enthalpy of

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formation for both parent molecules and radicals at each level of theory. An isodesmic reaction is a

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hypothetical reaction where the number and type of bonds is conserved on each side of the work reaction,

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and a homodesmic reaction conserves number and type of bonds, but also conserves hybridization27. The

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thermal enthalpy of each species in the work reaction is determined, which allows calculation of ∆Ho298

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reaction. Known, evaluated literature values ∆fHo298 of the three reference molecules are used with the

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calculated ∆Ho298 reaction, to determine the standard enthalpies of formation of the target molecule. 4


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∆rxnHo298 = ∑ ∆ Hf (Products) - ∑ ∆ Hf (Reactants)

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The use of species, that have similar bond environments on both sides of the work reaction, provides a

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cancellation of systematic errors that may exist in the calculation of ∆fHo298 for each species and allows for

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an increase in accuracy for the standard enthalpy analysis.

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Internal Rotation Potentials about the C—C, C—OH, C—OOH, C—OO and O—OH bonds in the target

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molecules are needed to determine the lowest energy conformer and for internal rotor energy contributions to

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entropy and heat capacity versus temperature. Energy profiles for internal rotations were calculated to

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determine energies of the rotational conformers and inter-conversion barriers along with contributions to

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entropy and heat capacity for the low barrier (below 4.5 kcal mol-1) rotors. Frequencies calculated by the

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Gaussian code are examined by viewing the vibration mode movement; the contributions from frequencies

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corresponding to internal rotations are excluded from the entropy and heat capacity and replaced with a more

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accurate estimate of S and Cp(T) from the internal rotor contributions. The total energies as a function of the

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dihedral angles were computed at the B3LYP/6-31G(d,p) level of theory by scanning the torsion angles

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between 00 and 3600 in steps of 100, while all remaining coordinates were fully optimized. All potentials

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were rescanned when a lower energy conformer is found, relative to the initial low energy conformer. The

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total energy corresponding to the most stable molecular conformer was arbitrarily set to zero and used as a

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reference point to plot the potential barriers. The resulting potential energy barriers for internal rotations in

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the hydroperoxides, alcohols and peroxy radicals are shown in supporting information along with data for the

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potentials.

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Kinetic calculations

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Canonical transition state theory was used for reactions with potential barriers (saddle points) and minimum

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energy path, variational transition state analysis, was used for the barrierless R• + O2 association reaction.

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High-pressure rate constants were calculated as a function of temperature, from the thermochemical

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properties of the reactants, and the transition state structures through the following reaction:

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=

∆ ‡

∆ ‡

(1)

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Where kB is the Boltzmann constant, h is Planck’s constant, T is temperature, R is gas constant, ∆

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difference in entropy of reactants and transition state structures, and ∆

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reactants and transition state structures, with account for units of concentration.

‡

‡

is

is difference in enthalpy of

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The variational transition state theory (VTST) calculation for R• + O2 association reaction involved a

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potential energy scan along the forming bond at 0.1 Ao intervals with determination of the frequencies and

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structure at each of the points. Rate constants (canonical transition state theory) versus temperature were

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determined at each point and the minimum rate constant at each temperature (over the PE can) was

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identified. The variational rate constant was determined from the fit of the minimum rate constants to a

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modified Arrhenius equation.

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Kinetic parameters for the bimolecular chemical activation reactions, stabilization of each adduct (isomer)

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and for the subsequent unimolecular thermal dissociation reactions of the stabilized isomers were calculated

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by using a multifrequency quantum Rice Ramsperger-Kassel (QRRK)28-30 analysis for k(E). Reaction kinetic

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parameters for the chemically activated peroxy radical (adduct) formed from the R. + O2 association are

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reported to stabilized adduct and product channels as functions of pressure and temperature.

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RESULTS AND DISCUSSION

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Structures and internal rotor potentials

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Figure 1 illustrates the structures and nomenclature for the target molecules. Internal rotor potential

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diagrams for the hydroxyl and hydroperoxy rotors are illustrated in the supporting information Figures 1S-

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11S.

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y(c5h4do) cyclopentadienone

y(c5h3do)oh2 2-hydroxyl cyclopentadienone

y(c5h3do)q2 2-hydroperoxy cyclopentadienone

y(c5h3do)q3 3- hydroperoxy cyclopentadienone

y(c5h3do)oh3 3-hydroxyl cyclopentadienone

Figure 1 Structure and abbreviated nomenclature of the target molecules. Nomenclature: clockwise -

carbon site adjacent to the C=O group is 1, secondary vinylic carbon is 2, q is (ooh) group.

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The standard enthalpies of formation at 298.15 K of the reference species in the reactions are summarized in Table 1, along with their uncertainities.

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As an example the following equation is used to estimate ∆fHo298 for y(c5h4do). y(c5h4do) + cdccc → y(c5h6)

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∆fHo298 (kcal mol-1): Target

-0.15

+ cdccdoc

32.1

-27.40

The standard enthalpy of formation for each species in the reaction is calculated, and the enthalpy of reaction, ∆rxnHo298, is calculated. Literature values for enthalpies of formation of the three reference compounds (values above in bold) are used with the ∆rxnHo298 to obtained the enthalpy of formation on the target molecule, y(c5h4do) As an example the values in brackets below correspond to B3LYP/6-31 g(d,p) calculated values in Hartrees and resulting value is converted to kcal mol-1 using 627.51 kcal mol-1/Hartree. ∆rxnHo298 = [(-194.012906)+( -231.147354)] –[( -268.030211)+( -157.117923)] x 627.51 = -7.61 kcal mol-1 Using the calculated ∆rxnHo298 and reference species to find ∆fHo298 of the target molecule in kcal mol-1

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-7.61 kcal mol-1 = (-27.40) + (32.1) - (-0.15) - ∆fHo298 y(c5h4do).

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∆fHo298 y(C5h4dO) = 12.7 kcal mol-1

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The target molecule and radical structure corresponding abbreviated nomenclature are presented in Figures 1 and 2 respectively. Table 1 Standard Enthalpies of formation at 298.15 K of reference species used in work reactions Species cdcc y(c5h6) cdccdo cdccc cdccdoc y(c6h8) y(c6h6do) y(c6h12) y(c6h10do) y(c4h6) y(c4h4do) y(c6h10) y(c5h8) cdc cdcoh Benzene

∆fHo298 kcal mol-1 4.78 ± 0.19 32.1 ± 0.36 -16.7 ± 1.0 -0.15 ± 0.19 -27.4 ± 2.6 25.00 ± 0.15 -4.4 ± 2.4 -29.43 ± 0.19 -55.23 ± 0.21 38.53± 0.4 10.32 ± 1.0 -1.03 ± 0.2 8.10 ± 0.33 12.54 ± 0.1 -29.8 ± 2.0 19.8 ± 0.2

reference 31 31 33 35 37 39 40 42 43 45 46 47 31 31 49 51

Species cdcj y(c6h5)j cdcjc y(c4h4o) y(c4h3o)j2 cdccdc cdcjcdc cdccjdo cdccdcj y(c4h3o)j3 coh ccoh cccoh coj ccoj cccoj

∆fHo298 kcal mol-1 71 ± 1.0 81 ± 2.0 58.89 ± 0.12 -8.3 ± 0.2 61.67 ± 0.3 26.00 ± 0.19 75 ± 1 a 21.9 ± 1 a 85.4 ± 1 a 61.80 ± 0.3 -48.16 ± 0.07 -56.21 ± 0.1 -60.97 ± 0.12 5.02 ± 0.5 -3.1 ± 0.31 -7.91 ± 0.33

reference 32 32 34 36 38 35 41 41 44 38 31 31 31 48 50 50

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203 204 205 206 207

52 Phenol -23.03 ± 0.14 cq a 53 ccohdc -42.1 ± 1 ccq 40 y(c6h6do)2 -6.0 ± 2.4 cccq 56 cdcq -10.87 ± 1 a cooj 34 y(c6h5)q -2.68 ± 0.49 ccooj 58 cc -20.04 ± 0.07 cccooj 58 ccc -25.02 ± 0.12 cj 32 i-c4h9 17 ± 0.5 y(c4h4o) 60 y(c3h4do) 3.8 ± 1.0 cdcdo a Error not provided (error ± 1 assigned), y= cyclic, d= double bond,

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50 -30.93 ± 0.21 54 -39.9 ± 1.5 55 -44.37 ± 0.2 50 2.91 ± 0.21 57 -6.8 ± 2.3 50 -10.53 ± 0.26 32 35.1 ± 0.2 59 -8.3 ± 0.2 31 -11.35 ± 0.38 j= radical, q= ooh group

Uncertainty and Confidence Limits The error calculation is determined from comparison of calculated ∆Hrxn with the literature ∆Hrxn, on a set

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of twelve work reactions involving species with known, standard enthalpies of formation. Table 2 lists the

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12 reference reactions with ∆Hrxn calculated using known thermochemical values and with our calculated

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∆H work reaction energies. Overall of Root Mean Square (RMS) deviation values for the twelve reaction set

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are 0.48 kcal mol-1 for CBS-QB3 and 0.98 kcal mol-1 for B3LYP/6-31G(d,p). Table 3 lists the method

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uncertainty at 95% confidence limit obtained from this data versus number of work reactions. The values vs.

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number of reactions results from a limitation in number of reference species, which prevented the use of the

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same number of work reactions for each molecule or radical target. The uncertainty in enthalpy values of

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each reference species in each of the work reactions for our target molecules and radicals is also incorporated

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into the error analysis. Further calculation details for the reported uncertainties and the error limits for the

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reference species are included in the supporting information. The number of isodesmic reactions for each

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target molecule are listed in Table 4, which also includes the 95% confidence limits.

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Table 2 Comparison of Experiment ∆fHo298 with values from CBS-QB3 and B3LYP/6-31G(d,p) calculation (kcal mol-1) Reaction Experiment CBS_QB3 B3LYP/6-31G(d,p) coh + ccc → ccoh + cc -3.07 -2.95 -3.86 ccoh + ccc → cccoh + cc 0.22 -0.01 -0.15 cccoh + cc → ccoh + ccc -0.22 0.01 0.15 cdcc + cc → cdc + ccc 2.78 2.72 3.89 cj + cdcc → i-c4h9 -22.88 -22.21 -21.34 cdcj + cj → cdcc -101.32 -101.32 -102.05 y(c4h4o) + cdccdc → y(c5h6) + y(c3h4do) 18.20 18.77 18.55 Phenol + cc → y(c6h6) + ccoh 6.66 6.18 8.20 y(c6h5)oh + ccj → y(c6h5)j + ccoh 19.42 19.92 19.09 8


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222 223 224 225 226 227


cdcc + cdcdo → cdc + y(c3h4do) 22.91 23.67 23.86 y(c4h6) + cccoh → Phenol + ccc -6.88 -6.17 -8.05 cdcoh + Benzene → Phenol + cdc -0.49 0.05 0.70 RMS 0.48 0.98 Notation - y is cyclic, d is double bond, j is radical, Experiment data uses reference species in Table 1. This data is used to determine the ‘work reaction method’ uncertainty vs. number of work reactions used.

Table 3 Method Uncertainty for the Work Reaction Sets at Confidence 95% Limit in (kcal mol-1) Number of Work Reactions 7 5 4 3

228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254

CBS-QB3 0.44 0.59 0.76 1.18

B3LYP/6-31G(d,p) 0.90 1.21 1.54 2.42

Standard enthalpies of formation and for the stable parent molecules of cyclopentadienone, hydroxyl cyclopentadienones and cyclopentadienone-hydroperoxides are listed in Table 4.

Five to seven isodesmic reactions are used to determined ∆fHo298 of the species in Figure 1. Nomenclature – carbon site adjacent to the C=O group is 1, secondary vinylic carbon is 2, q is (ooh) group. The calculated standard enthalpies of formation and work reactions for each of these target parent molecules, with the corresponding uncertainty value including standard deviation, are listed in Table 4. The calculation values from CBS-QB3, which shows the lowest standard deviation and is the highest level calculation method in this study, are recommended. For one evaluation on the accuracy for enthalpy of formation values in this study, we calculated ∆fHo298 of the target cyclopentadienone y(c5h4do) using seven work reactions as shown in Table 4 This resulted in 13.0 ± 1.9 kcal mol-1 for ∆fHo298. This value is in agreement with the literature data (13.0 kcal mol-1) by Ormand et. Al.15, (13.2 kcal mol-1) by Wang and Brezinsky2, and by Burcat and Ruscic61, the data is 0.25 kcal mol-1 higher than work of Robinson and Lindstedt19 (12.75 kcal mol-1). Five isodesmic reactions schemes are used for evaluation the ∆fHo298 values on the cyclopentadienonealcohols, y(c5h3do)oh2 and y(c5h3do)oh3, where values show a 2.2 kcal mol-1 higher enthalpy for the 2 position alcohol relative to the 3 position, -31.3 ± 2.7 and -33.5 ± 2.7 kcal mol-1 respectively. Enthalpies of formation of two parent cyclopentadienone hydroperoxides, y(c5h3do)q2 and y(c5h3do)q3, were calculated with five isodesmic reactions. The enthalpies determined show that y(c5h3do)q2 is five kcal mol-1 higher in enthalpy at -8.2 ± 2.4 kcal mol-1, versus the lower enthalpy of y(c5h3do)q3 at -13.2 ± 2.4 kcal mol-1. 9



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255 256 257 258

Page 10 of 44

Table 4 Evaluated Enthalpies of Formation at 298 K of Target Molecules from the work reaction analysis

Work Reactions

CBS-QB3

y(c5h4do) y(c5h4do) + cdcc → y(c5h6)+ cdccdo y(c5h4do) + cdccc → y(c5h6) + cdccdoc y(c5h4do) + y(c6h8) → y(c5h6) + y(c6h6do) y(c5h4do) + y(c6h12) → y(c5h6) + y(c6h10do) y(c5h4do) + y(c4h6) → y(c5h6) + y(c4h4do) y(c5h4do) + y(c6h10) → y(c5h8) + y(c6h6do) y(c5h4do) + y(c5h8) → y(c4h6) + y(c6h6do) Average ∆fHo298 Standard Deviation y(c5h3do)oh2 y(c5h3do)oh2 + cdc → y(c5h4do) + cdcoh y(c5h3do)oh2 + benzene → y(c5h4do) + phenol y(c5h3do)oh2 + cdcc → y(c5h4do) + ccohdc y(c5h3do)oh2 + cdcc → y(c6h6do) + cdcoh y(c5h3do)oh2 + cdcc → y(c6h6do)2 + cdcoh Average ∆fHo298 Standard Deviation y(c5h3do)oh3 y(c5h3do)oh3 + cdc → y(c5h4do) + cdcoh y(c5h3do)oh3 + benzene → y(c5h4do) + phenol y(c5h3do)oh3 + cdcc → y(c5h4do) + ccohdc y(c5h3do)oh3 + cdcc → y(c6h6do) + cdcoh y(c5h3do)oh3+ cdcc → y(c6h6do)2 + cdcoh Average ∆fHo298 Standard Deviation y(c5h3do)q2 y(c5h3do)q2 + cdc → y(c5h4do) + cdcq y(c5h3do)q2 + benzene → y(c5h4do) + y(c6h5)q y(c5h3do)q2 + cc → y(c5h4do) + ccq y(c5h3do)q2 + cdcc → y(c6h6do) + cdcq y(c5h3do)q2 + cdcc → y(c6h6do)2 + cdcq Average ∆fHo298 Standard Deviation y(c5h3do)q3

∆fHo298 kcal mol-1 B3LYP/ Literature 6-31G(d,p)

12.3 ± 1.2 12.8 ± 2.7 13.7 ± 2.5 13.0 ± 0.7 13.8 ± 1.2 12.5 ± 2.5 13.0 ± 2.5 13.0 ± 1.9 0.55

12.0 ± 1.4 12.5 ± 2.8 15.6 ± 2.6 12.2 ± 1.0 13.8 ± 1.5 15.1 ± 2.6 16.3 ± 2.6 13.9 ± 2.1 1.76

-30.9 ± 2.8 -31.5 ± 2.0 -32.3 ± 2.2 -30.9 ± 3.2 -31.0 ± 3.2 -31.3 ± 2.7 0.59

-31.9 ± 3.0 -33.1 ± 2.2 -34.4 ± 2.5 -30.9 ± 3.4 -31.6 ± 3.4 -32.4 ± 2.9 1.39

-33.1 ± 2.8 -33.7 ± 2.0 -34.5 ± 2.2 -33.2 ± 3.2 -33.2 ± 3.2 -33.5 ± 2.7 0.59

-33.3 ± 3.0 -34.5 ± 2.2 -35.9 ± 2.5 -32.3 ± 3.4 -33.1 ± 3.4 -33.8 ± 2.9 1.39

-8.3 ± 2.2 -8.4 ± 2.0 -7.9 ± 2.5 -8.3 ± 2.7 -8.3 ± 2.7 -8.2 ± 2.4 0.17

-8.9 ± 2.4 -9.6 ± 2.3 -10.7 ± 2.7 -7.9 ± 2.9 -8.6 ± 2.9 -9.2 ± 2.6 1.07

13.22 12.7519 13.2061 13.015

10


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259 260 261


y(c5h3do)q3 + cdc → y(c5h4do) + cdcq -13.3 ± 2.2 -13.1 ± 2.4 y(c5h3do)q3 + benzene → y(c5h4do) + y(c6h5)q -13.4 ± 2.0 -13.8 ± 2.3 y(c5h3do)q3 + cc → y(c5h4do) + ccq -12.9 ± 2.5 -15.0 ± 2.7 y(c5h3do)q3 + cdcc → y(c6h6do) + cdcq -13.3 ± 2.7 -12.1 ± 2.9 y(c5h3do)q3 + cdcc → y(c6h6do)2 + cdcq -13.3 ± 2.7 -12.9 ± 2.9 o -13.4 ± 2.6 Average ∆fH 298 -13.2 ± 2.4 Standard Deviation 0.17 1.07 Notation - y is cyclic, d is double bond, j is radical, q is (ooh) group, 2 is carbon beta to carbonyl. CBSQB3 values recommended, standard deviation is for the method work reaction sets.

y(c5h3do)j2

y(c5h3do)j3

y(c5h3do)oj2

y(c5h3do)oj3

y(c5h3do)ooj2

y(c5h3do)ooj3

y(c5h3do)oh2-3j

y(c5h3do)oh2-4j

y(c5h3do)oh2-5j

y(c5h3do)oh3-2j

y(c5h3do)oh3-4j

y(c5h3do)oh3-5j

y(c5h3do)q2-3j

y(c5h3do)q2-4j

y(c5h3do)q2-5j

y(c5h3do)q3-2j

y(c5h3do)q3-4j

y(c5h3do)q3-5j

262 11



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Page 12 of 44

263 264 265 266 267 268 269

Figure 2 Structure and abbreviated nomenclature of the cyclopentadienone radicals corresponding to the loss of a hydrogen atom from the parent molecules

270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286

Scheme 1 Nomenclature for C—H bond dissociation energy calculations in Table 5 for: • Cyclopentadienone, hydroxyl- and hydroperoxyl- cyclopentadienone vinylic radicals

Table 5 shows the results from the three to seven work reactions and the resulting standard enthalpies for the vinylic carbons, alkoxy and peroxy radicals listed in the scheme below. The calculated enthalpies of the parent cyclopentadienone and of the radicals corresponding to loss of a hydrogen atom with ∆Hf Hydrogen atom (52.1 kcal mol-1 at 298.15 K)61 allow calculation of the corresponding C—H bond dissociation energies.

Cyclo-pentadienone-2yl: (y(c5h3do)j2 Cyclo-pentadienone-3yl: y(c5h3do)j3 Cyclo-pentadienone-2-hydroxyl-3-yl: y(c5h3do)oh2-3j Cyclo-pentadienone-2-hydroxyl-4-yl: y(c5h3do)oh2-4j Cyclo-pentadienone-2-hydroxyl-5-yl: y(c5h3do)oh2-5j Cyclo-pentadienone-3-hydroxyl-2-yl: y(c5h3do)oh3-2j Cyclo-pentadienone-3-hydroxyl-4-yl: y(c5h3do)oh3-4j Cyclo-pentadienone-3-hydroxyl-5-yl: y(c5h3do)oh3-5j Cyclo-pentadienone-2-hydroperoxyl-3-yl: y(c5h3do)q2-3j Cyclo-pentadienone-2-hydroperoxyl-4-yl: y(c5h3do)q2-4j Cyclo-pentadienone-2-hydroperoxyl-5-yl: y(c5h3do)q2-5j Cyclo-pentadienone-3-hydroperoxyl-2-yl: y(c5h3do)q3-2j Cyclo-pentadienone-3-hydroperoxyl-4-yl: y(c5h3do)q3-4j Cyclo-pentadienone-3-hydroperoxyl-5-yl: y(c5h3do)q3-5j • O—H bond dissociation energies for cyclopentadienone to form an alkoxy radical Cyclo-pentadienone-alkoxyl-2-yl: (y(c5h4do)oj2 Cyclo-pentadienone-alkoxyl-3-yl: y(c5h4do)oj3 • OO-H bond dissociation energies for cyclopentadienone to form a peroxy radical Cyclo-pentadienone-peroxyl-2-yl (y(c5h3do)ooj2 Cyclo-pentadienone-peroxyl-3-yl: y(c5h3do)ooj3. ----------------------------------------------------------------------------------------------------------------------------------------Nomenclature – carbon site adjacent to the C=O group is 1, secondary vinylic carbon is 2, q is (ooh) group. Structures of radical species are illustrated in the Figure 2.

287 288

Bond Dissociation Enthalpies (BDE)

289

The C—H bond dissociation Enthalpies are reported from the calculated ∆fHo298 of the parent molecule and

290

the radical corresponding to loss of hydrogen atom at the respective carbon or oxygen site. The enthalpies of

291

the parent molecule and of the product radical are calculated and used with the value of 52.1061 kcal mol-1 for

292

the H atom to determine the corresponding BDE. The individual BDE values computed from isodesmic

293

work reaction enthalpies of formation are listed in Table 5.

294 295

The data in Table 5 list the standard enthalpy for cyclopentadienone -2yl radical (117.4), which is 3.6 kcal

296

mole-1 stronger than the C—H bond on cyclopentadienone-3yl radical (113.8). The 3-yl C—H bond is

297

similar to that on benzene50 (113.5 kcal mol-1); but the -2yl bond is significantly stronger. The presence of an

298

alcohol, a hydroperoxide, or a peroxy group on a carbon adjacent to the C-H bond increase bond dissociation

299

enthalpy by an average of 0.5 kcal mol-1.

300

Table 5 Enthalpies of Formation at 298 K and Bond Dissociation Enthalpy (BDE) for Radicals ∆fHo298 kcal mol-1 Work Reactions CBS-QB3 B3LYP/ 12


Page 13 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


6-31g(d,p) y(c5h3do)j2 y(c5h3do)j2 + cdc → y(c5h4do) + cdcj y(c5h3do)j2 + benzene → y(c5h4do) + y(c6h5)j y(c5h3do)j2 + cdcc → y(c5h4do) + cdcjc y(c5h3do)j2 + y(c4h4o) → y(c5h4do) + y(c4h3o)j y(c5h3do)j2 + cdccdc → y(c5h4do) + cdcjcdc y(c5h3do)j2 + cdccdo → y(c5h4do) + cdccjdo y(c5h3do)j2 + cdccdc → y(c5h4do) + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)j3 y(c5h3do)j3 + cdc → y(c5h4do) + cdcj y(c5h3do)j3 + benzene → y(c5h4do) + y(c6h5)j y(c5h3do)j3 + cdcc → y(c5h4do) + cdcjc y(c5h3do)j3 + y(c4h4o) → y(c5h4do) + y(c4h3o)j2 y(c5h3do)j3 + cdccdc → y(c5h4do) + cdcjcdc y(c5h3do)j3 + cdccdo → y(c5h4do) + cdccjdo y(c5h3do)j3 + cdccdc → y(c5h4do) + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h4do)oj2 y(c5h3do)oj2 + coh → y(c5h3do)oh + coj y(c5h3do)oj2 + ccoh → y(c5h3do)oh + ccoj y(c5h3do)oj2 + cccoh → y(c5h3do)oh + cccoj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oj3 y(c5h3do)oj3 + coh → y(c5h3do)oh2 + coj y(c5h3do)oj3+ ccoh → y(c5h3do)oh2 + ccoj y(c5h3do)oj3 + cccoh → y(c5h3do)oh2 + cccoj Average ∆fHo298 Standard Deviation BDE y(c5h3do)ooj2 y(c5h3do)ooj2 + cooh → y(c5h3do)q + cooj y(c5h3do)ooj2 + ccooh → y(c5h3do)q + ccooj y(c5h3do)ooj2 + cccooh → y(c5h3do)q + cccooj Average ∆fHo298

78.6 ± 2.2 76.5 ± 2.8 77.3 ± 1.9 78.9 ± 2.0 79.3 ± 2.2 78.8 ± 2.4 78.6 ± 2.2 78.3 ± 2.2 1.01 117.3

75.6 ± 2.3 80.1 ± 2.9 78.7 ± 2.1 79.8 ± 2.1 82.1 ± 2.3 81.1 ± 2.5 78.6 ± 2.3 79.4 ± 2.4 2.12 118.5

75.1 ± 2.2 72.9 ± 2.8 73.8 ± 1.9 75.3 ± 2.0 75.8 ± 2.2 75.2 ± 2.4 75.1 ± 2.2 74.7 ± 2.2 1.01 113.8

71.8 ± 2.3 76.4 ± 2.9 75.0 ± 2.1 76.2 ± 2.1 78.4 ± 2.3 77.4 ± 2.5 74.9 ± 2.3 75.7 ± 2.4 2.12 114.8

-9.4 ± 3.1 -9.4 ± 3.1 -9.3 ± 3.1 -9.4 ± 3.1 0.02 74.1

-6.2 ± 3.7 -6.1 ± 3.7 -6.1 ± 3.7 -6.1 ± 3.7 0.08 77.3

-6.7 ± 3.1 -6.7 ± 3.1 -6.6 ± 3.1 -6.7 ± 3.1 0.02 79.0

-3.8 ± 3.7 -3.7 ± 3.7 -3.7 ± 3.7 -3.7 ± 3.7 0.08 81.9

27.7 ± 2.7 27.6 ± 3.8 28.2 ± 2.7 27.8 ± 3.1

28.8 ± 3.4 28.6 ± 4.4 29.3 ± 3.4 28.9 ± 3.8 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Standard Deviation BDE y(c5h3do)ooj3 y(c5h3do)ooj3 + cooh → y(c5h3do)q2 + cooj y(c5h3do)ooj3 + ccooh → y(c5h3do)q2+ ccooj y(c5h3do)ooj3 + cccooh → y(c5h3do)q2 + cccooj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh2-3j y(c5h3do)oh2-3j + cdc → y(c5h3do)oh + cdcj y(c5h3do)oh2-3j + cdccdo → y(c5h3do)oh+ cdccjdo y(c5h3do)oh2-3j + cdccdc → y(c5h3do)oh + cdcjcdc y(c5h3do)oh2-3j + cdccdc → y(c5h3do)oh + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh2-4j y(c5h3do)oh2-4j + cdc → y(c5h3do)oh + cdcj y(c5h3do)oh2-4j + cdccdo → y(c5h3do)oh+ cdccjdo y(c5h3do)oh2-4j + cdccdc → y(c5h3do)oh + cdcjcdc y(c5h3do)oh2-4j + cdccdc → y(c5h3do)oh + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh2-5j y(c5h3do)oh2-5j + cdc → y(c5h3do)oh + cdcj y(c5h3do)oh2-5j + cdccdo → y(c5h3do)oh+ cdccjdo y(c5h3do)oh2-5j + cdccdc → y(c5h3do)oh + cdcjcdc y(c5h3do)oh2-5j + cdccdc → y(c5h3do)oh + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh3-2j y(c5h3do)oh3-2j + cdc → y(c5h3do)oh2 + cdcj y(c5h3do)oh3-2j + cdccdo → y(c5h3do)oh2+ cdccjdo y(c5h3do)oh3-2j + cdccdc → y(c5h3do)oh2 + cdcjcdc y(c5h3do)oh3-2j + cdccdc → y(c5h3do)oh2 + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh3-4j

Page 14 of 44

0.31 88.1

0.37 89.2

23.9 ± 2.7 23.8 ± 3.8 24.3 ± 2.7 24.0 ± 3.1 0.31 89.3

24.6 ± 3.4 24.4 ± 4.4 25.2 ± 3.4 24.7 ± 3.8 0.37 90.1

33.7 ± 3.06 33.8 ± 3.22 34.4 ± 3.07 33.7 ± 3.07 33.9 ± 3.12 0.34 117.3

30.9 ± 3.35 36.4 ± 3.49 37.4 ± 3.35 33.9 ± 3.35 34.7 ± 3.40 2.93 118.1

30.2 ± 3.1 30.4 ± 3.2 31.0 ± 3.1 30.3 ± 3.1 30.5 ± 3.1 0.34 113.9

27.0 ± 3.4 32.6 ± 3.5 33.6 ± 3.4 30.1 ± 3.4 30.8 ± 3.4 2.93 114.2

34.6 ± 3.1 34.8 ± 3.2 35.4 ± 3.1 34.7 ± 3.1 34.9 ± 3.1 0.34 118.3

32.0 ± 3.4 37.5 ± 3.5 38.5 ± 3.4 35.0 ± 3.4 35.8 ± 3.4 2.93 119.2

33.9 ± 3.1 34.1 ± 3.2 34.7 ± 3.1 33.9 ± 3.1 34.2 ± 3.1 0.34 119.8

30.9 ± 3.4 36.5 ± 3.5 37.5 ± 3.4 34.0 ± 3.4 34.7 ± 3.4 2.93 120.4 14


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y(c5h3do)oh3-4j + cdc → y(c5h3do)oh2 + cdcj y(c5h3do)oh3-4j + cdccdo → y(c5h3do)oh2+ cdccjdo y(c5h3do)oh3-4j + cdccdc → y(c5h3do)oh2 + cdcjcdc y(c5h3do)oh3-4j + cdccdc → y(c5h3do)oh2 + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)oh3-5j y(c5h3do)oh3-5j + cdc → y(c5h3do)oh2 + cdcj y(c5h3do)oh3-5j + cdccdo → y(c5h3do)oh2+ cdccjdo y(c5h3do)oh3-5j + cdccdc → y(c5h3do)oh2 + cdcjcdc y(c5h3do)oh3-5j + cdccdc → y(c5h3do)oh2 + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)q2-3j y(c5h3do)q2-3j + cdc → y(c5h3do)q + cdcj y(c5h3do)q2-3j + cdccdo → y(c5h3do)q+ cdccjdo y(c5h3do)q2-3j + cdccdc → y(c5h3do)q + cdcjcdc y(c5h3do)q2-3j + cdccdc → y(c5h3do)q + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)q2-4j y(c5h3do)q2-4j + cdc → y(c5h3do)q + cdcj y(c5h3do)q2-4j + cdccdo → y(c5h3do)q+ cdccjdo y(c5h3do)q2-4j + cdccdc → y(c5h3do)q + cdcjcdc y(c5h3do)q2-4j + cdccdc → y(c5h3do)q + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)q2-5j y(c5h3do)q2-5j + cdc → y(c5h3do)q + cdcj y(c5h3do)q2-5j + cdccdo → y(c5h3do)q+ cdccjdo y(c5h3do)q2-5j + cdccdc → y(c5h3do)q + cdcjcdc y(c5h3do)q2-5j + cdccdc → y(c5h3do)q + cdccdcj Average ∆fHo298 Standard Deviation BDE y(c5h3do)q3-2j y(c5h3do)q3-2j + cdc → y(c5h3do)q2 + cdcj y(c5h3do)q3-2j + cdccdo → y(c5h3do)q2+ cdccjdo

30.2 ± 3.1 30.3 ± 3.2 30.9 ± 3.1 30.2 ± 3.1 30.4 ± 3.1 0.34 116.0

26.4 ± 3.4 32.0 ± 3.5 33.0 ± 3.4 29.5 ± 3.4 30.2 ± 3.4 2.93 115.8

31.7 ± 3.1 31.9 ± 3.2 32.5 ± 3.1 31.8 ± 3.1 32.0 ± 3.1 0.34 117.6

28.3 ± 3.4 33.9 ± 3.5 34.8 ± 3.4 31.4 ± 3.4 32.1 ± 3.4 2.93 117.7

56.8 ± 2.7 57.0 ± 2.9 57.6 ± 2.8 56.9 ± 2.7 57.1 ± 2.8 0.34 117.4

53.6 ± 3.0 59.1 ± 3.2 60.1 ± 3.1 56.6 ± 3.1 57.3 ± 3.1 2.93 117.7

53.8 ± 2.7 53.9 ± 2.9 54.5 ± 2.8 53.8 ± 2.7 54.0 ± 2.8 0.34 114.3

50.3 ± 3.0 55.9 ± 3.2 56.9 ± 3.1 53.4 ± 3.1 54.1 ± 3.1 2.93 144.40

57.5 ± 2.7 57.6 ± 2.9 58.2 ± 2.8 57.5 ± 2.8 57.7 ± 2.8 0.34 118.0

53.9 ± 3.0 59.5 ± 3.2 60.5 ± 3.1 57.0 ± 3.1 57.7 ± 3.1 2.93 118.06

55.2 ± 2.7 55.3 ± 2.9

52.1 ± 3.0 57.7 ± 3.2 15



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301 302 303

Page 16 of 44

y(c5h3do)q3-2j + cdccdc → y(c5h3do)q2 + cdcjcdc 55.9 ± 2.8 58.7 ± 3.1 y(c5h3do)q3-2j + cdccdc → y(c5h3do)q2 + cdccdcj 55.2 ± 2.7 55.2 ± 3.1 o 55.9 ± 3.1 Average ∆fH 298 55.4 ± 2.8 Standard Deviation 0.34 2.93 121.3 BDE 120.7 y(c5h3do)q3-4j y(c5h3do)q3-4j + cdc → y(c5h3do)q2 + cdcj 50.3 ± 2.7 46.7 ± 3.0 y(c5h3do)q3-4j + cdccdo → y(c5h3do)q2+ cdccjdo 50.4 ± 2.9 52.3 ± 3.2 y(c5h3do)q3-4j + cdccdc → y(c5h3do)q2 + cdcjcdc 51.0 ± 2.8 53.5 ± 3.1 y(c5h3do)q3-4j + cdccdc → y(c5h3do)q2 + cdccdcj 50.3 ± 2.7 49.8 ± 3.1 o 50.5 ± 3.1 Average ∆fH 298 50.5 ± 2.8 Standard Deviation 0.34 2.93 115.8 BDE 115.8 y(c5h3do)q3-5j y(c5h3do)q3-5j + cdc → y(c5h3do)q2 + cdcj 51.8 ± 2.7 48.5 ± 3.0 y(c5h3do)q3-5j + cdccdo → y(c5h3do)q2+ cdccjdo 52.0 ± 2.9 54.1 ± 3.2 y(c5h3do)q3-5j + cdccdc → y(c5h3do)q2 + cdcjcdc 52.6 ± 2.8 55.1 ± 3.1 y(c5h3do)q3-5j + cdccdc → y(c5h3do)q2 + cdccdcj 51.8 ± 2.7 51.6 ± 3.1 52.3 ± 3.1 Average ∆fHo298 52.0 ± 2.8 Standard Deviation 0.34 2.93 117.7 BDE 117.4 y = cyclic, d = double bond, j = radical, q = ooh group, BDE = Bond Dissociation Enthalpy, CBS-QB3 values are recommended, standard deviation is for the method work reaction sets.

304

Table 6 provides a comparison of the C—H, O—H, OO--H bond dissociation enthalpies for

305

cyclopentadienone related species and literature value for reference cyclic and linear compounds.

306 307

Table 6 Comparison of C—H, O—H, and OO—H bond dissociation enthalpies. C—H Bond Dissociation Enthalpies (kcal mol-1) O

O

O

Values for comparison

.

. +H

|

+H

117.4

120.6038

(cdcjcq + H) 110.1762 (cdcjc + H) 106.2834

H

CH3

(ccjdcc + H) 108.664

. +H O

118.7063

(cdcjcdo + H) 112.8265

O

O

.

+H

113.8

.

+H

120.7038

16


Page 17 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


O

O

O OH

O CH3

OH

+H

. O

+H

.

117.2

120.4566

O OOH

OOH

+H

. O

117.4 O

O OH

O CH3

OH

+H

.

113.9

O

+H

.

119.2266

O OOH

OOH

. O

+H

114.3

O

.

OH

.

OH

+H

O

O

O CH3

+H

118.3

120.8066

O

.

OOH

OOH

+H O

118.0 O

O

. OH O

+H

+H

119.8

OH

. O CH3

120.5166

O

. +H OOH

OOH

O

120.7 O

O

+H

.

OH

116.0

OH

O

+H

.

O CH3

120.9766

O

+H

.

OOH O

OOH

115.8

O

.

.

117.6

OH

O

+H

+H

OH

O

O CH3

119.0566

O

. OOH

+H OOH

117.4

O—H Bond Dissociation Enthalpies (kcal mol-1)

17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

O

O OH

O

Page 18 of 44

.

.

O

+H

+ H 74.1

73.52

(cdccoj + H) 105.964 alkoxy radical

.

O

(cdcoj + H) 86.464 +H O

vinoxy radical

89.1034

O

+H

+H

.

OH

.

79.0

O

O

83.22

OO—H Bond Dissociation Enthalpies (kcal mol-1) O

O

.

+H O

OO

OO

OOH

88.1

O

H

+H OOH

OO

.

.

+H OO

85.6667

(cdcc(ooj) + H) 86.6162 (c(ooj)cdo + H) 87.2868

. +H

89.3

85.0467

(cdc(ooj)c + H) 84.8134 (ccdc(ooj)c + H) 85.5234

OO .

Peroxy radical +H

86.0634

308 309

Radical sites are indicated by a • or a j, d represents a double bond, q represents a hydroperoxide group (OOH).

310

The C—H bond dissociation enthalpies are important properties that relate the respective reactivity / stability

311

at specific carbon sites. Table 6 lists and compares BDE values of this study with that of the literature,

312

where data are available.

313

•

C—H bond dissociation enthalpy for the carbonyl-vinylic site [y(c5h3do)j2] is 117.4 kcal mol-1.

314

This is lower than the corresponding bond on furan by 1-3 kcal mol-1 and higher than on benzene by

315

~ 4 kcal mol-1.

316

•

317 318

similar to that on benzene. • •

323

C—H bond dissociation enthalpies for 2-hydroxyl-4-yl and 2-hydroperoxyl-4-yl sites [y(c5h3do)oh24j and y(c5h3do)q-3j] are 113.9 and 114.3 kcal mol-1 respectively.

321 322

C—H bond dissociation enthalpies for 2-hydroxyl-3-yl and 2-hydroperoxyl-3-yl sites [y(c5h3do)oh23j and y(c5h3do)q-2j] are 117.2 and 117.4 kcal mol-1 .

319 320

C—H bond dissociation enthalpy for secondary vinylic-3-yl site [y(c5h3do)j3] is 113.8 kcal mol-1 ,

•

C—H bond dissociation enthalpies for 2-hydroxyl-5-yl and 2-hydroperoxyl-5-yl sites [(y(c5h3do)oh2-5j and y(c5h3do)q-3j] are 118.3 and 118.0 kcal mol-1 respectively.

18


Page 19 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

324


•

325 326

similar to that on furans. •

C—H bond dissociation enthalpies for 3-hydroxyl-4-yl and 3-hydroperoxyl-4-yl sites [(y(c5h3do)oh3-4j and y(c5h3do)q3-4j] are 116. 0 and 115.8 kcal mol-1 respectively.

327 328

C—H bond dissociation enthalpy for 3-hydroxyl-2-yl sites [(y(c5h3do)oh3-2j] is 119.8 kcal mol-1 ,

•

C—H bond dissociation enthalpies for 3-hydroxyl-5-yl and 3-hydroperoxyl-5-yl sites

329

[(y(c5h3do)oh3-5j and y(c5h3do)q3-5j] are 117.6 and 117.4 kcal mol-1 about 2 kcal mol-1 weaker than

330

the C—H bond on furans.

331

•

Replacing a H atom on a vinylic carbon of cyclopentadienone with either a hydroxyl or

332

hydroperoxide affects the C—H bond energies on the other vinylic carbons differently; but the

333

respective carbon site differences are near constant , that is they vary by less than 1 kcal mol-1

334

(between 0.2-0.9 kcal mol-1) regardless of hydroxyl or peroxide moiety.

335 336

Alkoxy and Peroxide bonds

337

RO—H bond dissociation enthalpies for different alcohols forming an alkoxy radical site on the ring.

338

•

O—H bond dissociation enthalpies at alkoxyl-2-yl site [y(c5h3do)oj2] is 74.1 kcal mol-1 that close to

339

the 1,3-C5H5O reference species from Wang and Brezinsky2 (73.5 kcal mol-1), and lower than a

340

phenol - phenoxy radical by more than 10 kcal mol-1.

341 342 343

•

ROO—H bond dissociation enthalpies for peroxy radical sites on the ring. •

OO—H bond dissociation enthalpies at peroxyl-2-yl site [y(C5H3DO)OOJ2] is 88.1 kcal mol-1, which is stronger linear alkyl peroxides by 2-3 kcal mol-1.

344 345

O—H bond dissociation enthalpies at alkoxyl -3-yl site [y(c5h3do)oj3] is 79.0 kcal mol-1 .

•

OO—H bond dissociation enthalpies at peroxyl-3-yl site [y(C5H3DO)OOJ3] is 89.3 kcal mol-1 .

346 69 •

70

347

Reference enthalpy values (∆fHo298 ) for of OH radical 8.95 , OOH of 2.94

348

59.5561 all values in kcal mol-1 were used along with the parent molecule enthalpies for

349

determination of the BDE’s.

and for oxygen atom

350 351

Table 7 provides the C—OOH, RO—OH, and RO—O bond dissociations enthalpies from this study.

352 353 354 355

Table 7 Comparison of R—OH, R—OOH, RO—OH, RO--O bond dissociation enthalpies (kcal mol-1) 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Bond Dissociated

Page 20 of 44

C—OH Bond dissociation enthalpies

O

O

.

OH

O

. OH

118.5

. OH

117.1

+

O

+

.

OH

C—OOH Bond dissociation enthalpies O

O

.

OOH

O

.

+

O

.

+

.

OOH

90.9

OOH

Bond Dissociated

RO—OH Bond dissociation enthalpies

O

O

O

OOH

.

.

+

O

7.8 OH

Hydroperoxide not stable

O

.

+

.

OOH

OO

.

O

O O

RO—O Bond dissociation enthalpies

. +

O

15.5

OH

Bond Dissociated O

.O

22.4

O

OO .

356

89.5

OOH

.

+

.O

28.9

O

radical site is represented by •

357 358

Ring opening reactions of the cyclopentadienone vinylic radicals

359 360 361 362 363

Enthalpy of formation for species y(c5h3do)j2 and y(c5h3do)j3 were obtained from the CBS-QB3 calculation method as listed in Table 5. Canonical transition state theory was used to calculate the ring opening kinetic parameters for Cyclo-pentadienone-2yl [y(c5h3do)j2] and Cyclo-pentadienone-3yl [y(c5h3do)j3] radicals. The M062X71 and ωB97X72 hybrid density functional theory methods were used with the 6-311+G(d,p) basis set, along with the composite CBS-QB322 level of theory. There are two paths, both 20


Page 21 of 44

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364 365 366

beta scissions for ring opening reaction of Cyclo-pentadienone-2yl radical; one is to transition state (TS3) at 35.6 kcal mol-1 as shown in Table 8 forming C≡C-C(=O)C=C•. A second is TS1 to form C•=C--C=C=C=O with a barrier of 30.7; both barriers are at the CBS-QB3 level.

367 368 369

A barrier of 23.7 kcal mol-1 exists for the y(c5h3do)j3 radical for the ring opening, beta scission reaction to form C≡CC=C-C•=O from the Cyclo-pentadienone-3yl radical. High pressure limit rate parameter expressions in Table 9 are calculated based on B3LYP/CBSB7 structures.

370 371

Table 8 Ring opening reactions of Cyclo-pentadienone-2yl and Cyclo-pentadienone-3yl radicals. Enthalpies of reactants , transition state structures and products, kcal mol-1. Methods

Reactant

TS1

Product Ea

372 373 374 375

M062X/6-311+G(d,p) ώB97X/6-311+G(d,p) CBS-QB3

y(c5h3do)j2 78.3 78.3 78.3

TS1 110.4 112.0 109.0

cj=c--c=c=c=o 98.2 101.0 102.1

32.1 33.7 30.7

M062X/6-311+G(d,p) ώB97X/6-311+G(d,p) CBS-QB3

y(c5h3do)j3 74.7 74.7 74.7

TS2 98.0 100.9 98.4

c≡c-c=c-cj=o 69.1 70.5 72.4

23.3 26.2 23.7

y(c5h3do)j2 TS3 c≡c-c(=o)c=cj M062X/6-311+G(d,p) 78.3 116.3 100.3 38.0 78.3 117.6 103.0 39.3 ώB97X/6-311+G(d,p) CBS-QB3 78.3 113.9 102.3 35.6 Note: unit is kcal mol-1, y= cyclic ring, d = double bond, t = triple bond, TS = transition state, Ea Calculated Energy barrier to beta scission ring opening reaction (298 K)

Table 9 High pressure-limit rate parameters for ring opening reactions (298 – 2000 K) k = A(T)nexp(−E/RT) cm3/mol.s

Reactions

n

E (kcal mol-1)

1.0 x 1011

0.93

30.7

10

1.15

23.7

10

1.30

35.6

A

y(c5h3do) j2 → TS1→ cj=c--c=c=c=o y(c5h3do) j3 → TS2→ c≡c-c=c-cj=o y(c5h3do) j3 → TS3→ c≡c-c(=o)c=cj

3.6 x 10

1.1 x 10

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 44

376 377

R . + O2 Potential Energy Surface, Chemical Activation and Unimolecular Dissociation Reactions

378 379 380 381

Figures 3 and 4 show potential energy diagrams for the chemical activation reactions of O2 addition with the 2 and 3 carbon radical sites on cyclopentadienone and the further reactions involving: stabilization to ROO•, RO• + O (chain branching), intramolecular H atom transfers from the carbon atom sites to the peroxy radical, and intramolecular peroxy radical additions to the ipso carbons which form dioxiranes and dioxetanes.

382 383 384 385 386 387

The C2 and C3 carbon radical sites on the ring have deep R• + O2 → ROO• reaction well depths of 50.5 and 50.8 kcal mol-1 respectively. The enthalpy of reaction (∆HoRXN) for the chain branching reaction to cleave the RO—O bond is only 22.4 and 29 kcal mol-1 for the c2 and c3 peroxy sites as shown in Figures 3 and 4 and Table 5. The reactions of the peroxy radicals back to parent radical + O2, which in conventional alkane peroxy radicals often dominate over the branching reactions, each have an endothermicity (barrier) of slightly over 50 kcal mol-1 and will not be competitive.

388 389 390 391 392 393 394

Reactions involving intramolecular hydrogen transfer reactions from the carbon sites on the ring to the peroxy radical sites are also illustrated. The activation enthalpy (Ea) for this reaction on the y(c5h3do)ooj2 peroxy radical to form y(c5h3do)q2-3j is 10 kcal mol-1 or more above that of the RO + O branching channels. The y(c5h3do)ooj3 peroxy radical can abstract a hydrogen atom from two different carbon sites (intramolecular hydrogen transfer reaction), forming products y(c5h3do)q3-2j and y(c5h3do)q3-4j. The barriers to these H atom transfers are more than 13 kcal mol-1 above the branching path and the H transfer reactions are not calculated to be important – see kinetics diagrams vs. 1000/T(K) below.

395 396 397 398 399 400 401 402 403

There is one low energy reaction path that competes with the chain branching reactions in the cyclopentadienone 2 and 3 peroxy radical systems: this is the ipso addition of the peroxy radical to the ring forming a di-oxirane ring, and it is important in both the C2 and C3 peroxy radicals. The peroxy radical adds to the carbon site of the peroxide group (ipso addition) forming cyclopentadienone-2-dioxirane [ycpdo-2y(oo)] and cyclopentadienone-3-dioxirane [ycpdo-3-y(oo)] from the respective radicals. The respective barriers are 22.8 and 24.4 kcal mol-1, which are a few kcal mol-1 lower than the branching as shown in the potential energy (PE) diagrams, Figures 3 and 4. The transistion states to the dioxirane rings have tighter transition structures than the branching path. The low barriers make these product channels competitive with the chain branching reaction (RO + O).

404 405 406 407

The intramolecular peroxy radical addition reactions that result in a four member (oxetane) rings, shown in Figures 3 and 4, have barriers that are near 10 kcal mol-1 higher than the chain branching and dioxirane ring paths. The R• + O2 reactions to RO• + O chain branching reactions will be important paths when the cyclopentadienone carbon radicals are formed in combustion systems.

408 409 410 411 412 413

The thermochemical properties along with the forward and reverse rate constants (high-pressure limit) are calculated for each elementary reaction step. There are no publications on hydrogen transfer reactions

on aromatic systems or near aromatic systems that include a carbonyl oxygen on the ring system such as this cyclopentadienone nor are there any transition state energies for O atom or O2 association / dissociations, that we are aware of for comparisons. In separate studies we have compared our transition state calculation values with data from a number of other publications; 22


Page 23 of 44

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414 415 416 417 418 419 420 421 422 423

these include two alkyl systems of isooctane73-74, and on the ring carbon of toluene75. The comparison values show good agreement among the studies.

424 425 426

The chemical activation reaction kinetic results versus temperature and pressure are presented in Figures 5ad and 6a-d for the Cyclo-pentadienone-2-yl radical and Cyclo-pentadienone-3-yl radical systems, respectively.

Multi frequency quantum Rice Ramsperger-Kassel (QRRK) analysis is used for k(E)28-30 and master equation analysis76-78 is used for falloff. The QRRK-Master equation analysis is described by Chang et al28. The calculation of the state distributions use a set of 3n-6 frequencies in the form represented by sets of three frequencies that accurately reproduce the heat capacity curve of each adduct, where n is number of atoms in the adduct plus energy levels of one external rotation28. Tables 10 and 11 list the high pressure-limit, elementary rate parameters used as input data to the QRRK calculations, along with the Lennard Jones collision diameters, well depths (e/K) and .

Enthalpy (kcal mol-1)

+ O2

+o2

80

y(c5h3do)j

78.3

67.8 TS

60

+O +O

56 TS

y(c5h3do)oj

66 TS y(c5h3do)q-2j

57.1

ycpdo-4,5-y(cooc)

56.9 TS 50.6

50.2 40

y(c5h3do)ooj

27.8

ycpdo-2y(oo)

20

21.4

427 428

Figure 3 Potential Energy diagram for Reactions of Cyclo-pentadienone-2-yl + O2 (TS=Transition State)

429

(298K).

430

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 44

Enthalpy (kcal mol-1)

+O2

80 y(c5h3do)j2

74.7

69.9

70.7

TS

TS

67.2 65.6

TS

TS 60

+O

56.1 TS

y(c5h3do)oj2

52.9

y(c5h3do)q2-1j

ycpdo-3,4-y(cooc)

55.4

y(c5h3do)q2-3j

53.9

50.5

ycpdo-4,5-y(cooc)

44.9

40

TS

48.3

ycpdo-3-y(oo)

y(c5h3do)ooj2

24.7

23.9

431 432

20

433

Figure 4

434

(TS=Transition State) (298 K)

Potential Energy Diagram for Reactions of Cyclo-pentadienone-3-yl radical with O2

435 436 437

Table 10 High pressure-limit rate parameters for Cyclo-pentadienone-2-yl radical + O2 reactions

438

(298 – 2000 K) k = A(T)nexp(−E/RT) cm3 mol-1sec-1

Reactions

A

N

E (kcal mol-1)

y(c5h3do)j2 + o2 → y(c5h3do)ooj2

1.6 x 107

1.84

0.0

y(c5h3do)ooj2 → y(c5h3do)j2 + o2

18

3.2 x 10

-1.17

50.5

y(c5h3do)ooj2 → y(c5h3do)oj2 + o

5.7 x 1012

0.26

28.2

y(c5h3do)ooj2 → y(c5h3do)q2-3j

2.0 x 1011

0.49

40.2

y(c5h3do)ooj2 →ycpdo-4,5-y(cooc)

2.6 x 1012

-0.06

38.7

12

0.06

23.3

y(c5h3do)ooj2 → ycpdo-2-y(oo)

3.1 x 10

439 440

Input parameters include Lennard Jones collision diameter 6.23 Angstroms, e/k (Kelvin) 670 for well

441

depth, 900 cal mol-1. Complete input file for the Chemaster27 calculation is included in the

442

supporting information.

443 24


Page 25 of 44

log k

1 atm 13 12 11 10 9 8 7 6 5

y(c5h3do)ooj2 y(c5h3do)j2+o2 y(c5h3do)oj2+o y(c5h3do)q2-3j cpdo-4,5-y(cooc) 0

1

2

3

4

cpdo-2-y(oo)

1000/T

444 445

5-a

50 atm

log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


14 13 12 11 10 9 8 7 6 5

y(c5h3do)ooj2 y(c5h3do)j2+o2 y(c5h3do)oj2+o y(c5h3do)q2-3j cpdo-4,5-y(cooc) cpdo-2-y(oo) 0

1

2

3

4

1000/T

446 447

5-b

25



298 K 12

log k

11 10

y(c5h3do)ooj2

9

y(c5h3do)j2+o2

8

y(c5h3do)oj2+o

7

y(c5h3do)q2-3j

6

cpdo-4,5-y(cooc)

5

cpdo-2-y(oo) -3

-2

-1

0

1

2

log P 448 449

5-c

1000 K

log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 44

13 12 11 10 9 8 7 6 5 4

y(c5h3do)ooj2 y(c5h3do)j2+o2 y(c5h3do)oj2+o y(c5h3do)q2-3j cpdo-4,5-y(cooc) cpdo-2-y(oo) -3

-2

-1

0

1

2

log P 450 451

5-d

452 453

Figure 5 a-d Reactions of Cyclo-pentadienone-2-yl + O2. Figures 5 a and 5b show rate constants 3 -1 (log k, cm mol sec-1) vs temperature (1000/T) at 1 and 50 atm respectively. Figures 5c and 5d present

454 455

rate constants (log k, cm3 mol-1sec-1) vs Pressure (log P, atm) at 298 and 1000 Kelvin.

456

Results from the QRRK / Master Equation analysis show that two channels are competitive under

457

combustion temperatures: the chain branching (RO• + O) and the product from the ipso intramolecular

458

peroxy addition (cyclopentadienone-2-dioxirane). Stabilization is important at lower temperatures. Figure 5a

459

shows stabilization (cyclo-pentadienone-peroxyl-2-yl), is the most important channel up to 400 K. at 1 atm 26


Page 27 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


460

pressure, with the di-oxirane ring (cyclopentadienone-2-dioxirane) with the chain branching RO + O

461

(y(c5k3do)oj+o) slightly lower. Above 400 K the stabilization shows falloff and the dioxirane and the RO• +

462

O channels dominate. The dioxirane path is slightly higher between 400 and 1000K and the chain branching

463

dominates above 1000K. At 50 atm pressure, Figure 5b shows that stabilization (Cyclo-pentadienone-

464

peroxyl-2-yl) is the most important product up to 1000 K. Near 1000 K stabilization, chain branching and

465

dioxirane formation are competitive. The chain branching dominates over formation of dioxirane from 1000

466

K through the higher temperatures as stabilization shows rapid falloff. The intramolecular hydrogen atom

467

transfer reactions to form a hydroperoxide and alkenyl radical are several orders of magnitude lower.

468 469

Figure 5c illustrates the rate constants as a function of pressure at 298K. At pressures of 1 atm and above the

470

stabilized Cyclo-pentadienone-peroxyl-2-yl is the dominant channel and the cyclopentadienone-2-dioxirane

471

and y(c5k3do)oj+o

472

cyclopentadienone-2-dioxirane and the chain branching paths [y(c5k3do)oj+o] are the dominate reactions

473

below 1 atm pressure.

474

Figure 5d shows rate constants versus pressure at 1000 K. the cyclopentadienone-2-dioxirane and the chain

475

branching channel are near equal and dominate over the entire pressure range with stabilization only

476

approaching these two main channels at 100 atm. Intramolecular hydrogen atom transfer reactions are low

477

and considered not important.

products are lower.

Stabilization falls off rapidly below 1 atm, and the

478 479

Figures 6a and 6b illustrate the rate constants for the cyclo-pentadienone-3-yl radical reactions with 3O2

480

versus temperature at 1 and 50 atmospheres. Table 11 High pressure-limit rate

kbi= A(T)nexp(−E/RT) cm3 mol-1 sec-1; kuni sec-1

parameters for Cyclo-pentadienone-3A

n

E (kcal mol-1)

y(c5h3do)j3+ o2 → y(c5h3do)ooj3

2.4 x 106

2.04

0.0

y(c5h3do)ooj3 → y(c5h3do)j3 + o2

4.9 x 1017

-0.91

50.7

y(c5h3do)ooj3 → y(c5h3do)oj3 + o

5.1 x 1012

0.45

32.1

11

0.50

46.1


11

1.4 x 10

0.54

46.9


3.8 x 1011

0.28

41.9


2.0 x 1011

0.34

43.5

12

0.34

24.6

yl + O2 radical reactions for input to the Chemaster Calculations .Reactions


y(c5h3do)ooj3→ ycpdo-3-y(oo)

2.5 x 10

4.6 x 10

27



481 482 483

1 atm 14 y(c5h3do)ooj3

12

y(c5h3do)j3+o2

log k

10

y(c5h3do)oj3+o 8

y(c3h5do)q3-2j

6

y(c3h5do)q3-4j

4

ycpdo-4,5-y(cooc)

2

ycpdo-3,4-y(cooc) 0

1

2

3

4

ycpdo-3-y(oo)

1000/T

484 485

6-a

50 atm 14 y(c5h3do)ooj3

12

y(c5h3do)j3+o2

10 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 44

y(c5h3do)oj3+o 8

y(c3h5do)q3-2j

6

y(c3h5do)q3-4j

4

ycpdo-4,5-y(cooc)

2

ycpdo-3,4-y(cooc) 0

1

2

3

4

ycpdo-3-y(oo)

1000/T

486 487

6-b

488

28


Page 29 of 44

log k

298 K 12 11 10 9 8 7 6 5 4 3 2

y(c5h3do)ooj3 y(c5h3do)j3+o2 y(c5h3do)oj3+o y(c5h3do)q3-2j y(c5h3do)q3-4j ycpdo-4,5-y(cooc) ycpdo-3,4-y(cooc) -3

-2

-1

0

1

2

ycpdo-3-y(oo)

log P

489 490

6-c

491

1000 K 14 12

log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


y(c5h3do)ooj3

10

y(c5h3do)j3+o2

8

y(c5h3do)oj3+o

6

y(c5h3do)q3-2j

4

y(c5h3do)q3-4j ycpdo-4,5-y(cooc)

2

ycpdo-3,4-y(cooc) 0 -3

-2

-1

0

1

2

ycpdo-3-y(oo)

log P

492 493

6-d

494

Figures 6 a-d Reactions of Cyclo-pentadienone-3-yl + O2. Figures 6a and 6b show rate constants (log

495

k, cm3 mol-1sec-1) vs Temperature (1000/T) at 1 and 50 atm respectively. Figures 6c and 6d present rate

496

constants (log k, cm3 mol-1 sec-1) vs log ressure (log P, atm) at 298 and 1000 Kelvin respectively.

497

29



498

The cyclo-pentadienone-3-yl radical reaction with 3O2 shows similar results to that of the cyclo-

499

pentadienone-2-yl radical reactions. Figures 6a and 6b show rate constants vs. temperature: here the

500

stabilization dominates at temperatures below 500 K at 1atm and below 1000 K at 50 atm. The chain

501

branching (RO• + O) and the intramolecular peroxy ipso addition (cyclopentadienone-3-dioxirane) are

502

dominant at higher temperatures with the chain branching channel [y(c5h3do)oj3+o] being the higher.

503 504

Figures 6c and 6d show the rate constants for cyclo-pentadienone-3-yl radical reactions with 3O2 at

505

temperatures of 298 and 1000K versus log pressure. The results are similar to the cyclo-pentadienone-2-yl

506

radical system, where at 1000 K chain branching dominates over the entire pressure range and stabilization

507

only approaches the high pressure limit at 100 atm. The dioxirane ring formation channel is slightly lower

508

than the RO• + O branching channel. At 298 K, stabilization is the major product channel above 0.1 atm, and

509

the branching and dioxirane ring channels is dominant at pressures below 0.1 atm.

510 511

Overall the cyclopentadienone radical, chemical activation oxidation reactions show that the two major

512

reaction paths are reaction is to chain branching (RO• + O) and to dioxirane ring radical products in

513

temperature and pressure regions important to combustion systems. The products of the dioxirane reaction

514

paths and products need to be further evaluated.

515 516

1 atm 10 5 0 y(c5h3do)j2+o2 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 44

-5 y(c5h3do)oj2+o -10

y(c5h3do)q2-3j

-15

cpdo-4,5-y(cooc)

-20

cpdo-2-y(oo)

-25 0

1

2

3

4

1000/T

517 518

7-a

519 30


Page 31 of 44

50 atm 10 5 0 log k

y(c5h3do)j2+o2 -5 y(c5h3do)oj2+o -10

y(c5h3do)q2-3j

-15

cpdo-4,5-y(cooc)

-20

cpdo-2-y(oo)

-25 0

1

2

3

4

1000/T

520 521

7-b

298 K 0 -5 -10 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


y(c5h3do)j2+o2

-15

y(c5h3do)oj2+o -20

y(c5h3do)q2-3j

-25

cpdo-4,5-y(cooc)

-30

cpdo-2-y(oo)

-35 -4

-3

-2

-1

0

1

2

log P

522 523

7-c

31



1000 K 10 5 y(c5h3do)j2+o2

0 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 44

y(c5h3do)oj2+o -5

y(c5h3do)q2-3j cpdo-4,5-y(cooc)

-10

cpdo-2-y(oo) -15 -4

-3

-2

-1

0

1

2

log P

524 525

7-d

526

Figures 7a and 7b show rate constants (log k, sec-1) vs. (1000/T) at 1 and 50 atm for cyclopentadienyl -

527

2 peroxy radical dissociation. Figures 7c and 7d present the rate constants for the dissociation (log k,

528

sec-1) vs. (log P, atm) at 298 and 1000 K.

529 530

Unimolecular Dissociation of Cyclo-pentadienone-2-yl and Cyclo-pentadienone-3-yl peroxy radicals

531

Plots of rate constant versus 1000/T for dissociation of the stabilized peroxy adduct y(c5h3do)ooj2 at 1 and

532

50 atm pressure are illustrated in Figures 7a and 7b. The intramolecular peroxy ipso addition

533

(cyclopentadienone-2-dioxirane) and the chain branching (RO• + O) reactions are the dominant unimolecular

534

dissociation reaction channels under all conditions. At temperatures below 1000K the cyclic dioxirane

535

adduct dominates the chain branching, and at temperatures above 1000K, the chain branching and dioxirane

536

ring are similar at both pressures.

537 538

Plots of rate constant versus log pressure at 298 and 1000 K are illustrated in Figures 7c and 7d at 1 and 50

539

atm respectively. At 298 K this cyclo-pentadienone-2-yl peroxy radical dissociates to the dioxirane ring

540

adduct at several molecules per day over the entire pressure range. At 1000 K the dioxirane ring dominates

541

the chain branching at pressures above 5 atm the two channels are competitive.

542 543

The kinetic parameters for the cyclo-pentadienone-3-yl peroxy radical dissociation reaction 1 and 50 atm are

544

shown in Figures 8a and 8b. The dominant unimolecular reaction paths are similar to that of the cyclo32


Page 33 of 44

545

pentadienone-2-yl peroxy radical and are the dioxirane ring and chain branching paths. Here the reaction

546

paths are about one order of magnitude lower than those of the cyclo-pentadienone-2-yl peroxy radical

547

adduct. At pressures above 10 atm at 1000 K the cyclopentadienone-3-dioxirane formation reaction is the

548

dominant path with a smaller fraction to the chain branching.

549 550 551

The rate parameters versus pressure for chain branching and dioxirane formation reactions for Cyclo-

552

pentadienone-2-yl and Cyclo-pentadienone-3-yl peroxy radical system are tabulated in Table 12. Chemical

553

activation and unimolecular dissociation reaction rate parameters at pressures from 0.001 to 100 atm and

554

temperatures to 2000 K are in the supporting information.

555

1 atm 10 5 y(c5h3do)j3+o2

0 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


y(c5h3do)oj3+o

-5

y(c3h5do)q3-2j -10

y(c3h5do)q3-4j

-15

ycpdo-4,5-y(cooc)

-20

ycpdo-3,4-y(cooc) ycpdo-3-y(oo)

-25 0

1

2

3

4

1000/T

556 557

8-a

33



50 atm 10 5 y(c5h3do)j3+o2

log k

0

y(c5h3do)oj3+o

-5

y(c3h5do)q3-2j -10

y(c3h5do)q3-4j

-15

ycpdo-4,5-y(cooc)

-20

ycpdo-3,4-y(cooc)

-25

ycpdo-3-y(oo) 0

1

2

3

4

1000/T

558 559

8-b

560

298 K 0 -5 y(c5h3do)j3+o2 log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 44

-10

y(c5h3do)oj3+o

-15

y(c3h5do)q3-2j y(c3h5do)q3-4j

-20

ycpdo-4,5-y(cooc) -25

ycpdo-3,4-y(cooc)

-30

ycpdo-3-y(oo) -4

-3

-2

-1

0

1

2

log P

561 562

8-c

34


Page 35 of 44

1000 K

log k

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


8 6 4 2 0 -2 -4 -6 -8 -10 -12

y(c5h3do)j3+o2 y(c5h3do)oj3+o y(c3h5do)q3-2j y(c3h5do)q3-4j ycpdo-4,5-y(cooc) ycpdo-3,4-y(cooc) ycpdo-3-y(oo) -4

-3

-2

-1

0

1

2

log P

563 564 565 566 567 568

8-d Figures 8a and 8b show rate constants cyclopentadienyl -3 peroxy radical dissociation (log k, sec-1) vs Temperature (1000/T) at 1 and 50 atm, Figures 8c and 8d illustrate rate constants for the dissociation (log k, sec-1) vs Pressure (log P, atm) at 298 and 1000 Kelvin.

569 570 571

Table 12 Rate parameters for important paths in Cyclo-pentadienone-2-yl and Cyclo-pentadienone-3yl peroxy radical dissociations at different pressure (298 – 2000 K) Reactions Pressure k = A(T)nexp(−E/RT) sec-1

y(c5h3do)ooj2 → y(c5h3do)oj2+o

(atm)

A

n

E (kcal mol-1)

0.1

8.7 x 1049 7.0 x 1041

-12.05 -9.22

37.5 36.1

10

8.8 x 10

34

-6.88

34.6

50

1.9 x 1029

-5.02

33.1

0.1

7.3 x 1042

-9.89

31.2

1

2.2 x 10

35

-7.35

29.5

10

4.9 x 1029

-5.46

28.2

50

1.6 x 1025

-4

27.0

0.1

2.3 x 10

55

-13.59

43.0

3.0 x 10

45

-10.18

41.1

3.8 x 10

37

-7.52

39.3

3.6 x 10

31

-5.56

37.7

1

y(c5h3do)ooj2 → cpdo-2-y(oo)

y(c5h3do)ooj3 → y(c5h3do)oj3+o

1 10 50

35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

y(c5h3do)ooj3 → cpdo-3-y(oo)

Page 36 of 44

0.1

1.7 x 1043

-9.92

33.2

1

6.3 x 1034

-7.12

31.1

6.6 x 10

28

-5.15

29.7

2.9 x 10

24

-3.74

28.4

10 50 572 573 574

Entropy and Heat Capacity. Entropy and heat capacity values as a function of temperature are

575

determined from the calculated structures, moments of inertia, vibration frequencies, internal rotor

576

potentials, symmetry, electron degeneracy, number of optical isomers and the known mass of each

577

molecule. The calculations use standard formulas from statistical mechanics for the contributions of

578

translation, vibrations and external rotation (TVR) using the SMCPS (Statistical Mechanics – Heat

579

Capacity, Cp, and Entropy, S) program described in reference(79). This program utilizes frequencies

580

from the rigid-rotor-harmonic oscillator approximation along with moments of inertia from the

581

optimized B3LYP/6-31G(d,p) level.

582

Entropy and heat capacity contributions from torsion frequencies reported in Gaussian output were

583

replaced with the respective contributions from hindered internal rotors. Potential energy profiles

584

for internal rotations were calculated to determine energies of the rotational conformers and inter-

585

conversion barriers along with contributions to entropy and heat capacity for the low barrier rotors.

586

These are reported in the supplemental material. All internal: (R--OH) and hydroperoxide rotors

587

(R--OOH) and (RO--OH), were treated as hindered rotors. The contributions to entropy and heat

588

capacity of these internal rotors are calculated using ROTATOR80 code, which also accounts for

589

contributions to entropy from the optical isomers. Coupling of the low barrier internal rotors with

590

vibrations is not included. For hindered rotors, a relaxed rotational scan was done with dihedral

591

angle increments of 10o using B3LYP/6-31G(d,p) and the potential obtained was fitted to a

592

truncated Fourier series expansion of the form:

(2)

(3) 36


Page 37 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


593

The coefficients ao, ai, and bi were calculated to provide the minimum and maximum of the torsion

594

potentials with allowance for a shift of the theoretical angular positions. Where fi is relative energies

595

along with the rotational angle (θ) and m is number of angles in rotation.

596 597

The program ROTATOR uses the internal rotor potential to solve the 1-D Schrödinger equation in θ

598

and to calculate energy levels and the partition function of the hindered rotor. The program

599

calculates the Hamiltonian matrix in the basis of the wave function of free internal rotation and

600

performs the subsequent calculation of energy levels by diagonalization of the Hamiltonian matrix.

601

From the obtained partition functions, the contribution to entropy and heat capacity are determined

602

according to standard expressions of statistical thermodynamics. Entropy and heat capacity values

603

obtained from SMCPS and ROTATOR are summed with the TVR contributions above, and used to

604

calculate the entropy and heat capacity of the calculated species versus temperature. Entropy, So298,

605

and heat capacities, Cp(T), data of target molecules for 300-1500 K, are listed in Table 6, and the supporting

606

information include data for the studied species from 50 to 5000K.

607 608

Table 13 Ideal gas-phase thermochemical propertiesa vs. Temperature species

Cpo(T) cal mol-1 K-1

So 298 K

300 K

400 K

500 K

600 K

800 K

1000 K

1500 K

y(c5h4do)

69.3

19.6

25.4

30.1

33.8

39.2

42.9

48.3

y(c5h3do)oh2

75.9

24.1

30.4

35.6

39.8

45.8

49.6

54.5

y(c5h3do)oh3

76.1

24.7

31.2

36.3

40.2

45.5

49.0

53.9

y(c5h3do)q2

86.1

29.0

35.7

41.2

45.4

51.1

54.7

59.4

y(c5h3do)q3

86.1

29.1

35.7

40.8

44.6

50.1

53.7

58.8

y(c5h3do)j2

72.1

19.3

24.4

28.5

31.7

36.3

39.4

43.8

y(c5h3do)j3

71.8

19.3

24.5

28.6

31.8

36.3

39.4

43.9

y(c5h3do)oj2

72.1

19.3

24.4

28.5

31.6

36.3

39.4

43.8

y(c5h3do)oj3

71.8

19.3

24.5

28.6

31.8

36.4

39.4

43.9

y(c5h3do)ooj2

83.6

26.9

33.7

38.9

42.8

47.8

51.1

55.8

y(c5h3do)ooj3

83.4

26.9

33.1

38.0

41.9

47.2

50.6

55.1

y(c5h3do)oh2-3j

77.7

24.1

29.9

34.5

38.0

42.7

45.6

49.5

y(c5h3do)oh2-4j

77.3

23.9

29.7

34.4

38.0

43.0

46.1

49.9 37



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

609

Page 38 of 44

y(c5h3do)oh2-5j

78.8

23.9

29.6

34.3

38.0

43.0

46.1

49.9

y(c5h3do)oh3-2j

78.7

23.9

29.8

34.5

38.0

42.7

45.6

49.4

y(c5h3do)oh3-4j

78.6

23.7

29.3

33.7

37.1

41.9

45.0

49.2

y(c5h3do)oh3-5j

78.0

24.7

30.3

34.6

37.2

43.0

45.2

49.2

y(c5h3do)q2-3j

87.1

30.0

36.1

40.6

43.9

48.2

50.9

54.6

y(c5h3do)q2-4j

88.0

28.8

34.9

39.7

43.4

48.1

50.9

54.7

y(c5h3do)q2-5j

87.2

29.3

35.6

40.3

43.8

48.3

51.0

54.7

y(c5h3do)q3-2j

88.3

28.5

34.3

38.7

42.1

46.8

49.9

54.1

y(c5h3do)q3-4j

87.5

28.7

34.5

34.0

42.4

47.1

50.2

54.4

y(c5h3do)q3-5j

87.6

28.9

34.8

39.2

42.6

47.2

50.2

54.3

a

Units: Enthalpy kcal mol-1, Entropy and Heat Capacity cal mol-1 K-1

610 611

Summary

612

Thermochemical properties of cyclopentadienone and cyclo-pentadienone- alcohols, hydroperoxides, vinylic

613

radicals, alkoxy radicals and peroxy radicals are determined using Density Functional Theory B3LYP/6-

614

31G(d,p) and the CBS-QB3 higher level composite calculation method with use of isodesmic work reactions.

615

Standard enthalpy of formation (∆fHo298), entropy (So298) and heat capacity (CPo(T)) for cyclopentadienone

616

and corresponding 2-hydroxyl cyclopentadienone, 3-hydroxyl cyclopentadienone, 2-hydroperoxy

617

cyclopentadienone, and 3- hydroperoxy cyclopentadienone and related radical species are reported. Entropy

618

and heat capacity values versus temperature were also determined. The computed standard enthalpy of

619

formation of cyclopentadienone from this study is 13.0 ± 1.9 kcal mol-1 in agreement with data in the

620

literature. The standard enthalpy of formation for the 2-hydroxyl cyclopentadienone, 3-hydroxyl

621

cyclopentadienone, 2-hydroperoxy cyclopentadienone, and 3- hydroperoxy cyclopentadienone are -31.3 ±

622

2.7 kcal mol-1, -33.5 ± 2.7 kcal mol-1, -8.2 ± 2.4 kcal mol-1, and -13.2 ± 2.4 kcal mol-1, respectively. Bond

623

dissociation enthalpies for C—H, O—H, OO—H, C—OOH, R—OH, R—OOH, RO—OH, and RO—O

624

bonds on cyclopentadienone and the cyclopentadienone alcohols and hydroperoxides were also determined.

625

The vinylic C—H bond dissociation energies for parent cyclopentadienone are 113.8 and 117.4 kcal mol-1 for

626

the cyclo-pentadienone-2, and -3-yl peroxy radicals respectively. The RO—OH BDEs on the

627

cyclopentadienone y(c5h3do)oj2—OH and y(c5h3do)oj3—OH are very weak at 7.8 and 15.5 kcal mol-1

628

respectively. The RO—O BDEs on y(c5h3do)oj2—O and y(c5h3do)oj—O are also low at 22.4 and 29.0 kcal

629

mol-1 respectively. The R—OO BDEs on y(c5h3do) j2—OO and y(c5h3do)j3—OO BDEs are 50 kcal mol-1,

630

these are stronger than corresponding bonds on phenyl radical11 at 44.9 kcal mol-1 . The chemical activation

631

oxidation reactions, of the two vinylic radicals on cyclopentadienone with oxygen, show significant chain 38


Page 39 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


632

branching forming cyclo-pentadienone-2 and -3-yl alkoxy radicals (RO•) + oxygen atom ( O) products. The

633

branching is on the order of 50 % or higher in several important temperature and pressure ranges. One other

634

major new product, (other than stabilization to the peroxy adduct) from the oxidation reaction is formation of

635

a dioxirane ring on a carbon of a cyclopentenonyl radical.

636 637

Supporting Information

638

Figures 1S-11S provide potential energy profiles for target molecules with internal rotors. Tables 1S-2S

639

show example of uncertainty analysis calculations. Tables 3S-4S provide rate constant (log k) versus

640

temperature in different pressure condition of cyclo-pentadienone-2-yl and cyclo-pentadienone-3-yl radical

641

system. Tables 5S-6S presents reaction kinetic parameters, k = A(T/K)n exp(-Ea/RT) (300 < T/K< 2000),

642

for the cyclo-pentadienone-2-yl and cyclo-pentadienone-3-yl radical systems. Tables 7S-42S shows the

643

geometric parameters for stable, radical, and transition state molecules, from the B3LYP/CBSB7 level

644

calculations. Table 43S provide electronic energies, frequencies, and moments of inertia. Tables 44S-45S

645

present input parameters for Chemaster27 program. This information is available free of charge via the

646

Internet at http://pubs.acs.org.

647 648

39



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649

References

650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694

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695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740


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787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833


59. Guthrie, G. B.; Scott, D. W.; Hubbard, W. N.; Katz, C.; McCullough, J. P.; Gross, M. E.; Williamson, K. D.; Waddington, G., Thermodynamic Properties of Furan. J. Am. Chem. Soc. 1952, 74, 4662-4669. 60. Rodriguez, H. J.; Chang, J.-C.; Thomas, T. F., Thermal, Photochemical, and Photophysical Processes in Cyclopropanone Vapor. J. Am. Chem. Soc. 1976, 98, 2027-2034. 61. Burcat, A.; Ruscic, B., Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Table, Report Tae 960, 2005. 62. Lee, J.; Bozzelli, J. W., Thermochemical and Kinetic Analysis of the Allyl Radical with O2 Reaction System. Prepr. Pap.-Am. Chem. Soc. Div. Fuel Chem. 2004, 49, 439. 63. Catoire, L.; Swihart, M. T.; Gail, S.; Dagaut, P., Anharmonic Thermochemistry of Cyclopentadiene Derivatives. Int. J. Chem. Kinet. 2003, 35, 453-463. 64. Goldsmith, C. F.; Magoon, G. R.; Green, W. H., Database of Small Molecule Thermochemistry for Combustion. J. Phys. Chem. A 2012, 116, 9033-9057. 65. Jian, R. Thermochemical Properties of C3 to C5 Unsaturated Carbonyl Alkenes: Enthalpies of Formation, Entropy, Heat Capacity, Bond Enthalpy. New Jersey Institute of Technology, 2014. 66. Hudzik, J. M.; Bozzelli, J. W., Structure and Thermochemical Properties of 2-Methoxyfuran, 3Methoxyfuran, and Their Carbon-Centered Radicals Using Computational Chemistry. J. Phys. Chem. A 2010, 114, 7984-7995. 67. Auzmendi-Murua, I.; Bozzelli, J. W., Thermochemical Properties and Bond Dissociation Energies of C3 - C5 Cycloalkyl Hydroperoxides and Peroxy Radicals: Cycloalkyl Radical + 3o2 Reaction Thermochemistry. J. Phys. Chem. A 2012, 116, 7550–7563. 68. Lee, J.; Bozzelli, J. W., Thermochemical and Knetic Analysis of the Formyl Methyl Radical + O2 Reaction System. J. Phys. Chem. A 2003, 107, 3778-3791. 69. Baulch, D. L.; Bowman, C. T.; Cobos, C. J.; Cox, R. A.; Just, T.; Kerr, J. A.; Pilling, M. J.; Stocker, D.; Troe, J.; Tsang, W., et al. , Evaluated Kinetic Data for Combustion Modeling: Supplement Ii. J. Phys. Chem. Ref. Data 2005, 34, 757−1397. 70. Ruscic, B.; Pinzon, R. E.; Morton, M. L.; Srinivasan, N. K.; Su, M.; Sutherland, J. W.; Michael, J. V., Active Thermochemical Tables: Accurate Enthalpy of Formation of Hydroperoxyl Radical, Ho2. J. Phys. Chem. A 2006, 110, 6592-6601. 71. Zhao, Y.; Truhlar, D., The M06 Suite of Density Functionals for Main Group Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States, and Transition Elements: Two New Functionals and Systematic Testing of Four M06-Class Functionals and 12 Other Functionals. Theor. Chem. Acc. 2008, 120, 215-241. 72. Chai, J.-D.; Head-Gordon, M., Systematic Optimization of Long-Range Corrected Hybrid Density Functionals. J Chem Phys. 2008, 128, 084106. 73. Auzmendi-Murua, I.; Bozzelli, J. W., Thermochemistry, Reaction Paths, and Kinetics on the Secondary Isooctane Radical Reaction with 3o2. Int. J. Chem. Kinet. 2014, 46, 71-103. 74. Snitsiriwat, S.; Bozzelli, J. W., Thermochemistry, Reaction Paths, and Kinetics on the Tert-Isooctane Radical Reaction with O2. J. Phys. Chem. A 2014, 118, 4631−4646. 75. Da Silva, G.; Chen, C.-C.; Bozzelli, J. W., Toluene Combustion: Reaction Paths, Thermochemical Properties, and Kinetic Analysis for the Methylphenyl Radical + O2 Reaction. J. Phys. Chem. A 2007, 111, 8663-8676. 76. Dean, A. M., Predictions of Pressure and Temperature Effects Upon Radical Addition and Recombination Reactions. J. Phys. Chem. 1985, 89, 4600-4608. 77. Gilbert, R. G.; Luther, K.; Troe, J., Theory of Thermal Unimolecular Reactions in the Fall-Off Range. Ii. Weak Collision Rate Constants. Ber. Bunsen-Ges. Phys. Chem. 1983, 87, 169−177. 78. Gilbert, R. G.; Smith, S. C., Theory of Unimolecular and Recombination Reactions; Blackwell Scientific Publications: Oxford, 1990. 43



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834 835 836 837 838 839 840

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79. Sheng, C. Elementary, Pressure Dependent Model for Combustion of C1, C2 and Nitrogen Containing Hydrocarbons : Operation of a Pilot Scale Incinerator and Model Comparison. New Jersey Institute of Technology, 2002. 80. Lay, T. H.; Krasnoperov, L. N.; Venanzi, C. A.; Bozzelli, J. W.; Shokhirev, N. V., Ab Initio Study of ΑChlorinated Ethyl Hydroperoxides CH3CH2OOH, CH3CHCLOOH, and CH3CCL2OOH: Conformational Analysis, Internal Rotation Barriers, Vibrational Frequencies, and Thermodynamic Propertiesproperties. J. Phys. Chem. 1996, 100, 8240−8249.

841 842 843 844 845 846

"TOC Graphic" Enthalpy (kcal mol-1)

.+ O

2

80 Y(C5H3DO)J2 78.3 67.8

60

.

56

+O Y(C5H3DO)OJ2

66

.

.

Y(C5H3DO)Q2-3J

57.1

. YCPDO-4,5-Y(COOC) 56.9 50.6

50.2

40

847 848 849 850 851 852

20

. Y(C5H3DO)OOJ2 27.8

YCPDO-2Y(OO) 21.4

44


Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry

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