Thermochemical Properties and Bond Dissociation Energies for

Article pubs.acs.org/JPCA

Thermochemical Properties and Bond Dissociation Energies for Fluorinated Methanol, CH3−xFxOH, and Fluorinated Methyl Hydroperoxides, CH3−xFxOOH: Group Additivity Heng Wang and Joseph W. Bozzelli* Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, New Jersey 07102, United States S Supporting Information *

ABSTRACT: Oxygenated fluorocarbons are routinely found in sampling of environmental soils and waters as a result of the widespread use of fluoro and chlorofluoro carbons as heat transfer fluids, inert materials, polymers, fire retardants and solvents; the influence of these chemicals on the environment is a growing concern. The thermochemical properties of these species are needed for understanding their stability and reactions in the environment and in thermal process. Structures and thermochemical properties on the mono- to trifluoromethanol, CH3−xFxOH, and fluoromethyl hydroperoxide, CH3−xFxOOH (1 ≤ x ≤ 3), are determined by CBS-QB3, CBS-APNO, and G4 calculations. Entropy, S°298, and heat capacities, Cp(T)’s (300 ≤ T/K ≤ 1500) from vibration, translation, and external rotation contributions are calculated on the basis of the vibration frequencies and structures obtained from the B3LYP/6-31+G(d,p) density functional method. Potential barriers for the internal rotations are also calculated from this method and used to calculate hindered rotor contributions to S°298 and Cp(T)’s using direct integration over energy levels of the internal rotational potentials. Standard enthalpies of formation, ΔfH°298 (units in kcal mol−1) are CH2FOOH (−83.7), CHF2OOH (−138.1), CF3OOH (−193.6), CH2FOO• (−44.9), CHF2OO• (−99.6), CF3OO• (−153.8), CH2FOH (−101.9), CHF2OH (−161.6), CF3OH (−218.1), CH2FO• (−49.1), CHF2O• (−97.8), CF3O• (−150.5), CH2F• (−7.6), CHF2• (−58.8), and CF3• (−112.6). Bond dissociation energies for the R−OOH, RO−OH, ROO−H, R−OO•, RO−O•, R−OH, RO−H, R−O•, and R−H bonds are determined and compared with methyl hydroperoxide to observe the trends from added fluoro substitutions. Enthalpy of formation for the fluoro-hydrocarbon oxygen groups C/F/H2/O, C/F2/H/O, C/F3/O, are derived from the above fluorinated methanol and fluorinated hydroperoxide species for use in Benson’s Group Additivity. It was determined that fluorinated peroxides require interaction terms O/CH2F/O, O/CHF2/O, and O/CF3/O, as opposed to the common (O/C/O) group in hydrocarbons, resulting from interactions of the peroxide oxygen with the fluorines. Hydrogen bond dissociation increment (HBI) groups are also developed.

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INTRODUCTION Halogenated compounds are valued chemicals in industry,1 because of their high stability and low reactivity, but they are of concern to the environment because of their widespread use and their persistence in the environment. Mono-, di-, and trifluorinated methyl hydroperoxides and their corresponding radicals are intermediates in the atmospheric degradation of hydrofluorocarbons, which are often greenhouse gases. Their thermochemical properties are important to understanding the oxidation and reduction reactions1 in environmental and biological systems. A review2 on synthesis and decomposition of the saturated and unsaturated fluorinated peroxides has been published in 1996 by Sawada. Hayman et al.3 described the degradation of the fluorinated hydrocarbons and indicated that the fluorinated hydroperoxides and their radicals are important intermediates in the fluorocarbon degradation cycle. Schneider et al.1 focused on oxygenated trifluoromethyl compounds and concluded that substituting hydrogen atoms in the methyl group by fluorine © 2016 American Chemical Society

atoms shortened and therefore strengthened the C−O and O−O bonds, whereas substituting fluorine atoms by chlorine atoms increased the C−O and O−O bond lengths. El-Taher4 calculated the enthalpies of formation on fluorinated methyl peroxides with B3LYP, MP2(FULL), and MP4(SDTQ) methods and showed a stabilizing influence of fluorine-substituted methyl groups. El-Taher4 also presented bond dissociation energies for C−O, O−O, and O−H bonds in fluorinated methyl hydroperoxides. Reints et al.5 studied a series of O−O and O−H bond dissociation energies in monofluorinated to multiple fluorinated hydroperoxide molecules with several density functional theory calculation methods. In Reints et al.’s5 work, the bond dissociation energy of CF3O−H was reported as 118.8 kcal mol−1, which is near 14 kcal mol−1 stronger than the RO−H bond in methanol Received: May 25, 2016 Revised: July 27, 2016 Published: August 2, 2016 6998

DOI: 10.1021/acs.jpca.6b05293 J. Phys. Chem. A 2016, 120, 6998−7010

Article

The Journal of Physical Chemistry A Table 1. Standard Enthalpy of Formation for Reference Species in the Isodesmic Reactions (kcal mol−1) ΔfH°298

species

−56.54 ± −56.62 ± −65.42 ± −70.24 ± −108.07 ± −107.67 ± −120.87 ± −125.82 ± −166.71 ± −166.09 ± −180.51 ± −185.48 ± 34.98 ± 28.65 ± 24.21 ± 24.18i 52.10c 59.57c

CH3F CH3CH2F CH3CH2CH2F CH2F2 CH3CHF2 CH3CH2CHF2 CHF3 CH3CF3 CH3CH2CF3 CH3• CH3CH2• CH3CH2CH2• H O a

ΔfH°298

species

0.07a 0.48h 1.11a 1.30a 1.46a 0.48h 1.62a 1.65a 1.97a 0.48h 2.05a 2.15a 0.02c 0.07c 0.24g,j

−30.96 ± −38.94 ± −44.03 ± 2.37 ± −6.19 ± −11.35 ± −17.81 ± −20.05 ± −25.01 ± −30.07 ± 5.15 ± −3.01d 8.96 ± −47.97 ± −56.07 ± 2.94e,j −32.39 ± −32.37i

CH3OOH CH3CH2OOH CH3CH2CH2OOH CH3OO• CH3CH2OO• CH3CH2CH2OO• CH4 CH3CH3 CH3CH2CH3 CH3CH2CH2CH3 CH3O• CH3CH2O• OH CH3OH CH3CH2OH HOO• HOOH

0.67b 0.81b 0.67b 1.24b 0.92b 1.24b 0.01c 0.04c 0.06i 0.08i 0.08c 0.01c 0.04c 0.05i 0.04f,j

Wang.9 bWang.8 cRuscic.15 dBurke.16 eChase.17 fLuo.18 gBodi.19 hCsontos.21 iATcT table.20 jThe values we used in this study.

Table 2. Structural Parameters of Methyl Hydroperoxide and Mono- to Trifluoromethyl Hydroperoxides (Bond Lengths in Å, Dihedral Angles in Degrees) B(C−F) CH3OOH CH2FOOH CHF2OOH CF3OOH

1.3766 1.3507 1.3396 1.3327 1.3233 1.3215

B(C−O)

B(O−O)

B(O−H)

Φ(HO−OC)

Φ2(OO−CH)

1.4151 1.3814 1.3713

1.4399 1.4368 1.4349

0.9620 0.9637 0.9640

118.2 93.6 96.4

177.8 169.5 179.8

1.3712

1.4316

0.9642

96.4

179.6

and similar to the H−OH bond in water. They suggested that the CF3O• radical should be quite reactive toward hydrocarbons. Harvey et al.6 presented an experimental and theoretical calculation study on the halogenated methane derivatives. They combined the imaging photoelectron photoion coincidence (iPEPICO) spectrometry with G3B3 and W1 ab initio calculation methods, to investigate the thermochemical properties on energized species like CH2F+ as well as stable species, like CClF3. Kosmas et al.7 investigated the geometry and R−OOH bond dissociation energy of halogenated methyl peroxides (CHn+1X2−nOOH, X = F, Cl, Br, I) and concluded that increasing the halogen substitutions on the methyl group stabilized the molecular system and increased the R−C bond energy. They addressed the stability of the fluorinated hydroperoxides and specifically identified the weaker ROO−H and R−OOH bonds; they did not, however, characterize the very weak O−O bonds, which are the most likely to undergo dissociation reaction in a thermal environment. The enthalpy of formation of alkyl hydroperoxides8 and fluorinated hydrocarbons9 have been re-evaluated in our previous studies. In this study we employ these enthalpies of formation for the C1−C4 hydroperoxides and fluorinated hydrocarbons as reference species in work reactions to determine the enthalpy of formation of fluorinated methyl peroxides. Thermochemical properties are also determined for the corresponding alcohols, and the peroxy and alkoxy radicals with fluorine substitution on methyl group. These thermochemical properties

Table 3. Structural Parameters of Methyl Hydroperoxy and Mono- to Trifluoromethyl Hydroperoxy (Bond Lengths in Å, Dihedral Angles in Degrees) B(C−F) CH3OO• CH2FOO• CHF2OO• CF3OO•

1.3564 1.3333 1.3290 1.3174 1.3174 1.3156

B(C−O)

B(O−O)

Φ1(OO−CH)

1.4409 1.4184 1.4177

1.3241 1.3318 1.3304

180.0 164.2 163.9

1.4087

1.3324

180.0

are meant to serve as a reference data source for further development of thermochemical properties for larger fluorinated alcohols and peroxides, and for fluorinated aldehydes, esters, and acids.

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COMPUTATIONAL METHODS All values reported in this paper are for a standard state of 298 K and 1 atm. The absence of imaginary frequencies verified that all stable structures were true minima at their respective levels of theory. All calculations were performed using the Gaussian 0910 program. Because the G4, CBS-QB3, and CBS-APNO calculation methods have been successfully applied to fluoro hydrocarbons9 with small standard deviations, we continue the calculation of fluorinated alcohols and fluorinated hydroperoxides in this study with these three methods. 6999


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The Journal of Physical Chemistry A

The composite calculation method, CBS-QB3,12 utilizes the B3LYP/6-311G(2d,d,p) level of theory to optimize geometries and to calculate frequencies and then uses CCSD(T), MP4(SDQ), and MP2 calculations to determine single point energies. To compare and to provide an additional composite method calculation, CBS-APNO13 was also used. It performs an initial geometry optimization and frequency calculation at the HF/6-311G(d,p) level, followed by a higher-level QCISD/6-311G(d,p) geometry optimization. A single-point energy calculation is then performed at the QCISD(T)/ 6-311++G(2df,p) level, followed by extrapolation to the complete basis set limit. CBS-APNO is comparable to CCSD(T)/aug-cc-pVTZ which was shown in one of our previous studies.14 Enthalpies of Formation. Enthalpies of formation and bond dissociation energies were determined by averaging the results from isodesmic work reactions from CBS-QB3, CBS-APNO, and G4 calculation methods. Table 1 lists the standard enthalpy of formation for the reference species, which are used in the isodesmic work reactions along with their uncertainties. The enthalpy of formation of the fluorinated hydrocarbons9 and hydroperoxides are taken from our recent publications.8 The enthalpy of formation of small alkanes and their alkyl radicals are taken from Ruscic.15 Entropy and Heat Capacity. Entropy and heat capacity contributions for the 298−1500 K temperature range are determined from the calculated structures, moments of inertia, vibration frequencies, symmetry, electron degeneracy, number of optical isomers, and the known mass of each molecule. Vibration frequencies are scaled by a factor of 0.96422 for

Table 4. Important Geometry Parameters of Methanol and Mono- to Trifluoro Methanol (Bond Lengths in Å, Dihedral Angles in Degrees) B(C−F) CH3OH CH2FOH CHF2OH CF3OH

1.3808 1.3558 1.3558 1.3396 1.3396 1.3210

B(C−O)

B(O−H)

Φ1(HO−CH)

1.4176 1.3790 1.3541

0.9569 0.9590 0.9621

180.0 175.2 180.0

1.3463

0.9605

180.0

Table 5. Important Geometry Parameters of Methoxy and Mono- to Trifluoromethoxy (Bond Lengths in Å, Dihedral Angles in Degrees) B(C−F) CH3O• CH2FO• CHF2O• CF3O•

1.3757 1.3482 1.3482 1.3277 1.3272 1.3272

B(C−O) 1.3792 1.3313 1.3432 1.3598

The latest Gaussian-n family calculation, Gaussian-4 theory,11 optimized geometry and calculated frequency at the B3LYP/ 6-31G(2df,p) level, followed by a series of single point correlation energy calculations started from CCSD(T), MP4SDTQ, until MP2-Full were employed.

Figure 1. Potential energy profiles of the internal rotors of the methyl hydroperoxide and mono- to trifluoro hydroperoxides (a)−(d). The solid lines are the fit of the Fourier series expansions. Barriers decrease with increasing fluorine substitution. Numerical values in green are energies in kcal mol−1. 7000


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Figure 2. Potential energy profiles of the internal rotors of the methyl hydroperoxy and mono- to trifluoro hydroperoxy radicals (e)−(h). The solid lines are the fit of the Fourier series expansions. Numerical values in green are energies in kcal mol−1.

Table 6. Isodesmic Reactions and Heat of Formation for Fluoro Methyl Hydroperoxides ΔfH°298, kcal mol−1 isodesmic reactions

CBS-QB3

CBS-APNO

G4

CH2FOOH + CH4 = CH3OOH + CH3F CH2FOOH + CH3CH3 = CH3OOH + CH3CH2F CH2FOOH + CH3CH2CH3 = CH3OOH + CH3CH2CH2F CH2FOOH + CH3CH3 = CH3CH2OOH + CH3F CH2FOOH + CH3CH2CH3 = CH3CH2OOH + CH3CH2F CH2FOOH + CH3CH2CH2CH3 = CH3CH2OOH + CH3CH2CH2F CH2FOOH + CH3CH2CH3 = CH3CH2CH2OOH + CH3F CH2FOOH + CH3CH2CH2CH3 = CH3CH2CH2OOH + CH3CH2F method average average standard deviation for the work reaction set

−83.52 −83.69 −83.46 −83.59 −83.73 −83.57 −83.38 −83.58 −83.56 −83.74 0.12

−83.83 −84.02 −83.93 −83.95 −84.08 −84.05 −83.87 −84.07 −83.98

−83.57 −83.79 −83.85 −83.33 −83.59 −83.70 −83.61 −83.92 −83.67

0.09

0.19

CHF2OOH + CH4 = CH3OOH + CH2F2 CHF2OOH + CH3CH3 = CH3OOH + CH3CHF2 CHF2OOH + CH3CH2CH3 = CH3OOH + CH3CH2CHF2 CHF2OOH + CH3CH3 = CH3CH2OOH + CH2F2 CHF2OOH + CH3CH2CH3 = CH3CH2OOH + CH3CHF2 CHF2OOH + CH3CH2CH2CH3 = CH3CH2OOH + CH3CH2CHF2 CHF2OOH + CH3CH2CH3 = CH3CH2CH2OOH + CH2F2 CHF2OOH + CH3CH2CH2CH3 = CH3CH2CH2OOH + CH3CHF2 method average average standard deviation for the work reaction set

−137.77 −137.84 −137.83 −137.85 −137.87 −137.94 −137.63 −137.73 −137.81 −138.11 0.10

−138.36 −138.65 −138.78 −138.48 −138.71 −138.90 −138.41 −138.69 −138.62

−137.92 −138.30 −137.54 −137.67 −138.10 −137.39 −137.95 −138.43 −137.91

0.19

0.36

CF3OOH CF3OOH CF3OOH CF3OOH CF3OOH

−193.09 −192.93 −192.69 −193.17 −194.24

−193.81 −194.19 −194.19 −193.93 −194.24

−193.31 −193.71 −193.71 −193.07 −193.51

+ + + + +

CH4 = CH3OOH + CHF3 CH3CH3 = CH3OOH + CH3CF3 CH3CH2CH3 = CH3OOH + CH3CH2CF3 CH3CH3 = CH3CH2OOH + CHF3 CH3CH2CH3 = CH3CH2OOH + CH3CF3 7001


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The Journal of Physical Chemistry A Table 6. continued ΔfH°298, kcal mol−1 isodesmic reactions

CBS-QB3

CBS-APNO

G4

−192.80 −192.95 −192.82 −193.09 −193.56 0.49

−194.34 −193.85 −194.23 −194.10

−193.45 −193.35 −193.84 −193.49

0.20

0.25

CH2FOO• + HOOH = CH2FOOH + HOO• CH2FOO• + CH4 = CH2FOOH + CH3• CH2FOO• + CH3CH3 = CH2FOOH + CH3CH2• CH2FOO• + CH3CH2CH3 = CH2FOOH + CH3CH2CH2• CH2FOO• + CH3OOH = CH2FOOH + CH3OO• CH2FOO• + CH3CH2OOH = CH2FOOH + CH3CH2OO• CH2FOO• + CH3CH2CH2OOH = CH2FOOH + CH3CH2CH2OO• method average average standard deviation for the work reaction set

−44.38 −44.27 −44.66 −44.40 −44.53 −44.48 −44.70 −44.49 −44.90 0.16

−44.61 −45.57 −46.05 −45.85 −44.70 −44.71 −44.91 −45.20

−45.08 −45.06 −45.34 −44.81 −45.02 −45.11 −44.63 −45.01

0.61

0.23

CHF2OO• + HOOH = CHF2OOH + HOO• CHF2OO• + CH4 = CHF2OOH + CH3• CHF2OO• + CH3CH3 = CHF2OOH + CH3CH2• CHF2OO• + CH3CH2CH3 = CHF2OOH + CH3CH2CH2• CHF2OO• + CH3OOH = CHF2OOH + CH3OO• CHF2OO• + CH3CH2OOH = CHF2OOH + CH3CH2OO• CHF2OO• + CH3CH2CH2OOH = CHF2OOH + CH3CH2CH2OO• method average average standard deviation for the work reaction set

−98.35 −98.25 −98.64 −98.38 −98.51 −98.45 −98.68 −98.47 −99.26 0.16

−98.63 −99.59 −100.08 −99.87 −98.72 −98.73 −98.93 −99.22

−100.16 −100.15 −100.43 −99.89 −100.10 −100.20 −99.72 −100.09

0.61

0.23

CF3OO• + HOOH = CF3OOH + HOO• CF3OO• + CH4 = CF3OOH + CH3• CF3OO• + CH3CH3 = CF3OOH + CH3CH2• CF3OO• + CH3CH2CH3 = CF3OOH + CH3CH2CH2• CF3OO• + CH3OOH = CF3OOH + CH3OO• CF3OO• + CH3CH2OOH = CF3OOH + CH3CH2OO• CF3OO• + CH3CH2CH2OOH = CF3OOH + CH3CH2CH2OO• method average average standard deviation for the work reaction set

−152.72 −152.61 −153.00 −152.74 −152.87 −152.82 −153.04 −152.83 −153.76 0.16

−152.96 −153.92 −154.41 −154.20 −153.05 −153.06 −153.26 −153.55

−154.97 −154.96 −155.24 −154.70 −154.91 −155.01 −154.53 −154.90

0.61

0.23

CH2FOH + CH4 = CH3OH + CH3F CH2FOH + CH3CH3 = CH3OH + CH3CH2F CH2FOH + CH3CH2CH3 = CH3OH + CH3CH2CH2F CH2FOH + CH3CH3 = CH3CH2OH + CH3F CH2FOH + CH3CH2CH3 = CH3CH2OH + CH3CH2F CH2FOH + CH3CH2CH2CH3 = CH3CH2OH + CH3CH2CH2F method average average standard deviation for the work reaction set

−101.48 −101.65 −101.42 −101.84 −101.97 −101.81 −101.69 −101.94 0.22

−101.84 −102.04 −101.94 −102.22 −102.35 −102.32 −102.12

−101.61 −101.83 −101.90 −102.00 −102.26 −102.37 −102.00

0.21

0.28

CHF2OH + CH4 = CH3OH + CH2F2 CHF2OH + CH3CH3 = CH3OH + CH3CHF2 CHF2OH + CH3CH2CH3 = CH3OH + CH3CH2CHF2 CHF2OH + CH3CH3 = CH3CH2OH + CH2F2 CHF2OH + CH3CH2CH3 = CH3CH2OH + CH3CHF2 CHF2OH + CH3CH2CH2CH3 = CH3CH2OH + CH3CH2CHF2 method average average standard deviation for the work reaction set

−161.09 −161.16 −161.15 −161.45 −161.47 −161.55 −161.31 −161.59 0.18

−161.64 −161.92 −162.06 −162.02 −162.24 −162.44 −162.05

−161.17 −161.56 −160.80 −161.56 −161.99 −161.28 −161.40

0.25

0.33

CF3OOH + CH3CH2CH2CH3 = CH3CH2OOH + CH3CH2CF3 CF3OOH + CH3CH2CH3 = CH3CH2CH2OOH + CHF3 CF3OOH + CH3CH2CH2CH3 = CH3CH2CH2OOH + CH3CF3 method average average standard deviation for the work reaction set

7002


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The Journal of Physical Chemistry A Table 6. continued ΔfH°298, kcal mol−1 isodesmic reactions

CBS-QB3

CBS-APNO

G4

−217.53 −217.37 −217.13 −217.89 −217.68 −217.52 −217.52 −218.11 0.26

−218.21 −218.59 −218.62 −218.59 −218.90 −219.00 −218.65

−217.70 −218.11 −218.00 −218.09 −218.54 −218.48 −218.15

0.28

0.31

CH2FO• + CH3OH = CH2FOH + CH3O• CH2FO• + CH3CH2OH = CH2FOH + CH3CH2O• method average average standard deviation for the work reaction set

−49.30 −49.13 −49.22 −49.11 0.12

−49.12 −48.89 −49.00

−49.66 −48.56 −49.11

0.16

0.77

CHF2O• + CH3OH = CHF2OH + CH3O• CHF2O• + CH3CH2OH = CHF2OH + CH3CH2O• method average average standard deviation for the work reaction set

−97.59 −97.41 −97.50 −97.82 0.12

−97.86 −97.63 −97.75

−98.75 −97.65 −98.20

0.16

0.77

−149.93 −149.76 −149.84 −150.49 0.12

−150.63 −150.40 −150.51

−151.66 −150.56 −151.11

0.16

0.77

CH2F• + CH4 = CH3• + CH3F CH2F• + CH3CH3 = CH3CH2• + CH3F CH2F• + CH3CH2CH3 = CH3CH2CH2• + CH3F CH2F• + CH3CH3 = CH3• + CH3F CH2F• + CH3CH2CH3 = CH3CH2• + CH3CH2F CH2F• + CH3CH2CH3 = CH3• + CH3CH2CH2F method average average standard deviation for the work reaction set

−7.26 −7.65 −7.39 −7.43 −7.78 −7.20 −7.45 −7.61 0.28

−7.55 −8.03 −7.82 −7.74 −8.16 −7.65 −7.79

−7.38 −7.66 −7.13 −7.60 −7.92 −7.67 −7.52

0.34

0.20

CHF2• + CH4 = CH3• + CH2F2 CHF2• + CH3CH3 = CH3CH2• + CH2F2 CHF2• + CH3CH2CH3 = CH3CH2CH2• + CH2F2 CHF2• + CH3CH3 = CH3• + CH3CHF2 CHF2• + CH3CH2CH3 = CH3CH2• + CH3CHF2 CHF2• + CH3CH2CH3 = CH3• + CH3CH2CHF2 method average average standard deviation for the work reaction set

−58.26 −58.65 −58.39 −58.33 −58.68 −58.32 −58.45 −58.82 0.28

−58.89 −59.37 −59.16 −59.17 −59.59 −59.31 −59.13

−58.64 −58.92 −58.38 −59.02 −59.34 −58.26 −58.78

0.34

0.20

−111.87 −112.26 −112.00 −111.70 −112.05 −111.47 −112.06 −112.57 0.28

−112.58 −113.08 −112.86 −112.96 −113.38 −112.99 −112.82

−112.60 −112.88 −112.35 −113.01 −113.32 −112.90 −112.74

0.34

0.20

CF3OH + CH4 = CH3OH + CHF3 CF3OH + CH3CH3 = CH3OH + CH3CF3 CF3OH + CH3CH2CH3 = CH3OH + CH3CH2CF3 CF3OH + CH3CH3 = CH3CH2OH + CHF3 CF3OH + CH3CH2CH3 = CH3CH2OH + CH3CF3 CF3OH + CH3CH2CH2CH3 = CH3CH2OH + CH3CH2CF3 method average average standard deviation for the work reaction set

CF3O• + CH3OH = CF3OH + CH3O• CF3O• + CH3CH2OH = CF3OH + CH3CH2O• method average average standard deviation for the work reaction set

CF3• + CH4 = CH3• + CHF3 CF3• + CH3CH3 = CH3CH2• + CHF3 CF3• + CH3CH2CH3 = CH3CH2CH2• + CHF3 CF3• + CH3CH3 = CH3• + CH3CF3 CF3• + CH3CH2CH3 = CH3CH2• + CH3CF3 CF3• + CH3CH2CH3 = CH3• + CH3CH2CF3 method average average standard deviation for the work reaction set

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CF3OH is ∼5 kcal mol−1 lower than the value from Batt et al.,27 and our value for the trifluoromethoxy radical, CF3O•, is ∼6 kcal mol−1 higher than the enthalpy of formation reported by Batt et al.27 Batt et al. used the group additivity approach to estimate the enthalpies of formation of fluorinated species along with several bond energies. The work reactions that were used in this study have better systematic error cancellation compared to the group additivity estimation. In a couple of our previous studies9,28−32 in this research group, we indicated the interaction groups are needed when halogens are on adjacent carbons. Group additivity does not give correct enthalpies of formation for multi-halogenated hydrocarbons without the interaction group consideration. Our standard enthalpies of formation for CH2F•, CHF2•, and CF3•, are in agreement with the data of Kosmas et al.7 Substituting one F atom for a H atom on the methyl group of methyl hydroperoxide, methyl hydroperoxy, methanol, methoxy, and methane molecules results in a reduction of standard enthalpies of formation for the system ranging from 43 to 60 kcal mol−1, as illustrated under the “Diff column” in Table 7. Enthalpy values are taken from the lowest energy structure as determined from the evaluation of internal rotor potentials. There are a few PE curves that show conformers at 0.7−1 kcal mol−1 higher than the lowest energy conformers,

calculation of standard entropy and heat capacity at the B3LYP/6-31+G(d,p) level of calculation. As one of the most popular DFT (density functional theory) methods, B3LYP (the three-parameter Becke exchange functional, B3,23 combined with Lee−Yang−Parr correlation functional, LYP24) was used with the 6-31+G(d,p) basis set because of its economic cost and its capability of calculating larger molecules. The “SMCPS”25 program employing the rigid-rotorharmonic oscillator approximation from the frequencies along with moments of inertia from the optimized structure was used to determine the contributions of translation, external rotation, and vibrations. The “Rotator”23 program developed by Krasnoperov, Lay et al.26 was used to calculate the contributions from internal rotors from the corresponding internal rotor torsion frequencies. In this work, a ten-parameter Fourier series function is presented as a torsional potential curve to calculate the contribution of free internal rotation. The detailed function and parameters are shown in the Supporting Information.

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RESULTS AND DISCUSSION Geometries. The optimized geometries at the CBS-APNO for CH2FOOH, CHF2OOH, CF3OOH, CH2FOO•, CHF2OO•, CF3OO•, CH2FOH, CHF2OH, CF3OH, CH2FO•, CHF2O•, CF3O•, CH2F•, CHF2•, and CF3• are presented in the Supporting Information. The Cartesian coordinates, vibration frequencies, and moments of inertia are presented as Table S1−S3, respectively. Figure S16−S19 in the Supporting Information show important geometric parameters of target species. Structure comparisons on bond length and bond angle vs the fluorine substitution are listed in Tables 2−5. The F atom attached to the methyl group appears to undergo an interaction with the oxygen of the −OH in the −OOH group that results in an increased enthalpy value. Internal rotor barriers corresponding to the F atom rotation across the peroxy oxygen are significant: 13, 8, and 5 kcal mol−1 for CH2FOOH, CHF2OOH, and CF3OOH respectively; see Figure 1. The F atom in CH2FOOH undergoes hydrogen bonding to the peroxide hydrogen in the lowest energy configuration with a separation distance of 2.6 Å. Data in Tables 3 and 4 indicate that substation of F atoms for H atoms tends to strengthen the C−F and C−O bonds in the fluorinated methyl hydroperoxy species. Internal rotor barriers corresponding to the F atom rotation across the peroxy oxygen radical are 5, 3, and 2 kcal mol−1 for CH2FOO•, CHF2OO•, and CF3OO•, respectively. These barriers are less than half the corresponding barriers on the hydroperoxides. See Figure 2. Enthalpies of Formation. Table 6 lists the isodesmic reactions used to determine the enthalpy of formation of each target species by the three different calculation methods. The average of the three methods, in bold, is taken over the, up to eight, different isodesmic reactions. Table 7 summarizes the determined standard enthalpy of formation for each of the target species and compares the values with available literature data. Our standard enthalpies of fluoro hydroperoxide molecules, CH2FOOH, CHF2OOH, and CF3OOH, are in good agreement with the data of El-Taher,4 which were calculated at the B3LYP/6-311+G(2df,2p) level. Our standard enthalpies of CF3OH and CF3O• are in agreement with Schneider et al.1 The enthalpy of formation for

Table 7. Enthalpy of Formation of Each Target Molecules in This Study and Comparison with Available Literature (All in kcal mol−1) species CH3OOH CH2FOOH

ΔfH°298 −30.96 −83.7

ΔDiff a

literature values

b

52.8

−86.7,d,e −84.0,d,f −86.1,d,g −83.9,d,h −82.5k −144.0,d,e −139.1,d,f −142.6,d,g −138.3,d,h −136.9k −199.8,d,e −194.3,d,f −197.4,d,g −192.4,,d,h −191.0,d −191.9k,l

CHF2OOH

−138.1

54.4

CF3OOH

−193.6

55.5

CH3OO• CH2FOO• CHF2OO• CF3OO•

2.37b −44.9 −99.6 −153.8

47.3 54.4 54.5

CH3OH CH2FOH CHF2OH CF3OH

−47.97c −101.9 −161.6 −218.1

53.8 59.7 56.5

−217.7,i,l −213.5j,l

CH3O• CH2FO• CHF2O• CF3O•

5.15 ± 0.08c −49.1 −97.8 −150.5

54.3 48.7 52.7

−156.7,j,l −150.4i,l

CH3• CH2F• CHF2• CF3•

34.98c −7.6 −58.8 −112.6

42.6 51.2 53.8

−6.9k,l −57.6k,l −110.8,i,l −111.3k,l

a

Difference corresponding to substitution of one F atom for H atom. Wang.9 cRuscic.15 dEl-Taher.4 eMP2(FULL)/6-31G(d,p). fMP4(SDTQ)/6-311+G(d,p). gB3LYP/6-31G(d,p). hB3LYP/6-311+G(2df,2p). iSchneider.1 jBatt.27 kKosmas.7 lvia theoretical calculations.

b

7004


Article


Figure 3. Potential energy profiles of the internal rotors of the methanol and mono- to trifluoromethanols (i)−(l). The solid lines are the fit of the Fourier series expansions. Numerical values in green are energies in kcal mol−1.

substitution for a hydrogen shows the largest change in the R−O and O−H bond dissociation energies, relative to addition of the second and the third F atoms. The second F atom substitution results in a much stronger O−O bond than addition of the first and the third F atoms. Removing the terminal H atom in the peroxide group changes the RO−OH bond from the weakest to the strongest. The R−OO• bond energies are decreased to that of about onehalf of the R−OOH bonds. The RO−O• BDE of CH3O−O•, CH2FO−O•, CHF2O−O•, and CF3O−O• are 61, 55, 61, and 63 kcal mol−1, respectively, whereas the BDE of CH3−OO•, CH2F−OO•, CHF2−OO•, and CF3−OO• are 33, 37, 40, and 41 kcal mol−1, respectively. The R−OH bonds are 92, 103, 112, and 115 kcal mol−1 for methanol, monofluoromethanol, difluoromethanol, and trifluoromethanol. The R−O• bonds are 89, 101, 99, and 98 kcal mol−1 for methoxy, monofluoromethoxy, difluoromethoxy, and trifluoromethoxy. Group Additivity. Group additivity35 is a straightforward, valuable, and powerful method to estimate the thermodynamic properties of molecules for reaction analysis and use in detailed reaction modeling codes. Group additivity values are developed here for the mono- to trifluoromethanol and mono- to trifluoromethyl peroxides. In our previous study,9 we demonstrated the need for fluorine−fluorine non-nearest neighbor interaction groups to be included in the group additivity estimation of fluorocarbons when fluorine atoms are present on adjacent central (carbon) atoms. Similar interactions between the fluorine atom attached to central carbon and the peroxy oxygen atom in the C−OO oxygen are needed to accurately

which may contribute to the enthalpy. This study has not counted all the different structures to accurately determine the contribution of the higher energy conformers. Potential Energy Diagrams for Internal Rotors. Figure 1 shows the potential energy profiles for the two internal rotors in mono- to trifluoro hydroperoxide molecules as well as in the methyl hydroperoxide with peak energy values noted. Figure 2 shows the potential energy profiles for the internal rotors in mono- to trifluoro peroxy radicals as well as in the methyl peroxy radical. Figure 3 shows the potential energy profiles for the internal rotor in mono- to trifluoromethanol molecules as well as in the methanol. Entropy and Heat Capacity. Table 8 lists the standard entropy and heat capacities at 300, 400, 500, 600, 800, 1000, and 1500 K. TVR represents the sum of the contributions from translation, vibrations, and external rotations. Internal rotor indicates the contribution from hindered internal rotors, which replace the torsion frequency contributions in the TVR heat capacity and entropy data summations. Bond Dissociation Energies (BDE). Table 9 summarizes and compares the bond dissociation energies with available literature. For the bonding in the fluoro-substituted peroxide and peroxy radical groups, the ROO−H bonds are the strongest, about 90 kcal mol−1, which are about twice that of the RO−OH bonds, and about 10 kcal mol−1 stronger than the R−OOH bond, for the fluorinated species. Fluorine substitution tends to increase the bond dissociation energies, where the first F atom 7005


Article

The Journal of Physical Chemistry A Table 8. Ideal Gas Phase Entropy and Heat Capacity Obtained by B3LYP/6-31+G(d,p) Calculation (cal mol−1 K−1) CH2FOOH

CHF2OOH

CF3OOH

CH2FOH

CHF2OH

CF3OH

CH2FOO•

CHF2OO•

CF3OO•

CH2FO• CHF2O• CF3O• CH2F• CHF2• CF3• a

TVRa internal total TVR internal total TVR internal total TVR internal total TVR internal total TVR internal total TVR internal total TVR internal total TVR internal total TVR TVR TVR TVR TVR TVR

rotor

rotor

rotor

rotor

rotor

rotor

rotor

rotor

rotor

S°298

Cp300

Cp400

Cp500

Cp600

Cp800

Cp1000

Cp1500

64.28 6.73 71.01 67.82 8.60 76.42 68.78 9.09 77.87 60.42 2.62 63.04 64.35 4.53 68.87 65.46 4.40 69.86 65.34 5.99 71.33 69.10 6.09 75.20 70.10 6.64 76.74 61.57 65.86 68.03 54.99 59.89 63.37

12.38 5.67 18.05 14.52 4.90 19.42 17.18 3.96 21.14 10.57 1.82 12.39 12.65 3.40 16.04 15.20 1.35 16.55 12.09 2.35 14.44 14.40 2.05 16.45 17.02 2.22 19.24 10.96 12.95 15.66 9.64 10.13 12.05

15.22 5.12 20.34 17.66 4.58 22.24 20.57 4.03 24.61 12.80 2.07 14.86 15.28 3.66 18.94 18.16 1.24 19.40 14.64 2.06 16.70 17.20 2.09 19.29 20.11 1.95 22.05 13.13 15.37 18.16 10.77 11.66 13.86

17.78 4.78 22.56 20.28 4.27 24.55 23.16 4.01 27.17 14.93 2.15 17.08 17.51 3.41 20.92 20.40 1.17 21.57 16.93 1.86 18.78 19.51 2.02 21.53 22.40 1.71 24.12 15.04 17.31 20.00 11.81 13.00 15.25

19.91 4.59 24.50 22.35 4.02 26.36 25.08 3.93 29.00 16.76 2.14 18.90 19.29 2.99 22.28 22.06 1.12 23.18 18.81 1.72 20.53 21.31 1.91 23.22 24.07 1.54 25.61 16.60 18.81 21.33 12.70 14.07 16.27

23.08 4.36 27.44 25.24 3.64 28.89 27.59 3.65 31.24 19.60 1.99 21.59 21.83 2.27 24.10 24.22 1.07 25.30 21.59 1.53 23.11 23.79 1.68 25.47 26.16 1.33 27.50 18.91 20.85 22.99 14.12 15.60 17.58

25.33 4.14 29.47 27.16 3.35 30.51 29.12 3.36 32.48 21.68 1.81 23.48 23.55 1.83 25.38 25.55 1.05 26.59 23.48 1.40 24.89 25.34 1.51 26.85 27.33 1.22 28.55 20.52 22.14 23.90 15.22 16.61 18.31

28.77 3.56 32.33 29.92 2.86 32.78 31.14 2.84 33.98 24.93 1.48 26.41 26.10 1.36 27.45 27.34 1.02 28.36 26.22 1.23 27.46 27.39 1.27 28.66 28.63 1.10 29.73 22.85 23.85 24.92 17.05 18.04 19.13

TVR represents values from translation, vibrations, and external rotations.

describe the thermochemistry in these fluoroperoxide species. A resulting set of F/OO interactions or special O/CxF3−x/O groups are therefore developed to serve as an added component of the group additivity method; we term them “increments or increment groups”. The conventional groups for fluorinated methanols are listed in Table 10, and this table illustrates that the groups for fluoro methyl alcohols do not need added interaction terms, as the values are identical to those in Table 7. We now try to apply the enthalpies of formation for O/CxF3−x/O groups in Table 10 to calculate the enthalpies of formation for fluorinated methyl peroxides base on the groups in Table 11. Tables 10 and 11 illustrate that the calculated enthalpies of formation obtained for the fluorinated peroxides using the C/Fx/H3−x/O groups developed for the fluorinated methanols and the O/C/O and O/H/O groups of hydrocarbon peroxides are in error by 1.6−7.9 kcal mol−1. The enthalpies of formation for the fluoro peroxides are significantly off (in error) from the computationally calculated values obtained above in Table 7. The differences between each fluorinated methyl peroxide suggest that there is a C/Fx/H3−x/O interaction term between the fluorine on the carbon and oxygen of the peroxide that needs to be considered in the group additivity calculations for the fluoro hydroperoxide species.

In this study, we developed O/C3−xFx/O groups that take this C/Fx/H3−x/O interaction into account for the fluoro hydroperoxide species. Table 12 illustrates the group additivity calculation for fluorinated methyl peroxides using the new developed O/C3−xFx/O groups. Table 13 summarizes the enthalpies of formation for C/Fx/H3−x/O and a series of O/C3−xFx/O groups that have been developed. The standard entropy of C/F/H2/O is calculated as ΔS°298(CH 2FOH) = ΔS°298(C/F/H 2 /O) + ΔS°298(O/C/H) − R ln σ

where R = 1.987 cal mol−1 K−1 and σ is the symmetry number of the species, which is 1 for CH2FOH. ΔS°298(C/F/H 2 /O) = 63.04 − 29.07 + 1.987*ln(1) = 33.97 cal mol−1 K−1

The heat capacity of C/F/H2/O is calculated as Cp300(CH 2FOH) = Cp300(C/F/H 2 /O) + Cp300(O/C/H)

Cp300(C/F/H 2 /O) = 12.39 − 4.30 = 8.06 cal mol−1 K−1 7006


Article

The Journal of Physical Chemistry A Table 9. Summary and Comparison of Bond Dissociation Energies with Available Literature (Units in kcal mol−1) R = CH3

R = CH2F

R = CHF2

R = CF3

ROO−H

85.3 87.6a,b, 86.7a,c, 86.9a,d, 86.1a,e

90.9 95.0a,b, 93.8a,c, 94.2a,d, 93.3a,e

91.0 94.1a,b, 90.2a,c, 93.8a,d, 93.4a,e

91.9 94.5,a,b 93.4,a,c 94.1,a,d 93.5,a,e 95.1f

RO−OH

44.0 48.2a,b, 47.7a,c, 42.9a,d, 42.7a,e

43.6 47.9a,b, 46.8a,c, 40.5a,d, 39.9a,e

49.3 52.2a,b, 48.6a,c, 46.5a,d, 46.3a,e

52.0 49.5,a,b 53.2,a,c 48.9,a,d 49.5,a,e 49.7,f 49.4h

R−OOH

68.9 72.1a,b, 66.8a,c, 63.0a,d, 61.0a,e

79.1 83.8a,b, 77.2a,c, 72.3a,d, 69.9a,e, 72.9 g,

82.2 88.3a,b, 77.6a,c, 75.5a,d, 71.6a,e, 74.8g,

83.9 87.7,a,b 82.3,a,c 77.0,a,d 72.2,a,e 83.5,f 75.8g

RO−O•

61.3k

55.4

61.0

62.8 57.0 f

R−OO•

32.6k

37.3

40.4

41.2 37.0 f

R−OH

91.9l

103.3

111.7

114.5 116.2 f

RO−H

105.3l

104.9

115.9

119.7 119.4,f 118.8,h 124.7,i 117.5j

R−O•

89.4l

101.1

98.6

104.9l

100.8

101.4

97.5 99.2 f 106.2

R−H a

4 b

El-Taher. MP2(FULL)/6-31G(d,p). cMP4(SDTQ)/6-311+G(d,p). dB3LYP/6-31G(d,p). eB3LYP/6-311+G(2df,2p). fSchneider.1 gKosmas.7 h Reints.5 iHuey.33 jAsher.34 kWang.8 lRuscic.15

Table 10. Groups for Fluorinated Methanol with Use of C/Fx/H3−x/O Groups group 1 group 2 ΔfH298a a

CH2FOH

ΔfH°298a

CHF2OH

ΔfH°298

CF3OH

ΔfH°298

C/F/H2/O O/C/Hb

−64.0 −37.9 −101.9

C/F2/H/O O/C/H

−123.7 −37.9 −161.6

C/F3/O O/C/H

−180.2 −37.9 −218.1

Units in kcal mol−1. bCohen.36 Values are identical to values in Table 7.

Table 11. Groups for Fluorinated Methyl Hydroperoxides with Use of O/C/O Groups for Fluoro Methyl Hydroperoxides versus Values Obtained from Table 7

Table 13. Enthalpy of Formation for Fluoro Oxyhydrocarbon Groups (Units in kcal mol−1)

CH2FOOH

CHF2OOH

CF3OOH

group 1 C/F/H2/O group 2 O/C/O group 3 O/H/O calcd ΔfH°298a from group −85.3 additivity −83.7 calcd ΔfH°298a,b from work reactions (Table 7) needed interaction groups F/OO 1.6

C/F2/H/O O/C/O O/H/O −145.0

C/F3/O O/C/O O/H/O −201.5

−138.1

−193.6

F2/OO

6.9

F3/OO

a

7.9

Units in kcal mol−1. bInteraction groups are needed to account for fluorine/peroxide oxygen interactions.

Table 12. Groups for Fluorinated Methyl Hydroperoxides with O/C3−xFx/O Groups CH2FOOH

CHF2OOH

CF3OOH

C/F/H2/O O/CH2F/O O/H/O

C/F2/H/O O/CHF2/O O/H/O

C/F3/O O/CF3/O O/H/O

ΔfH°298

group

ΔfH°298

−64.0 −123.7 −180.2 −37.9a

O/CH2F/O O/CHF2/O O/CF3/O O/H/O

-3.4 1.9 2.9 −16.3a

Cohen.36

Table 14 lists the standard entropy and heat capacities for C/Fx/H3−x/O and O/C3−xFx/O groups. Hydrogen Bond Increments. The hydrogen-bond increment (HBI) method for group additivity of radical species, as developed by Lay et al.,37 was implemented for the fluorinated alkoxy and hydroperoxy radicals. The HBI method allows calculation of the thermochemical properties of radicals with only one group addition to that of the parent molecules. HBI groups include the bond energy and intrinsic increments corresponding to differences between the parent and corresponding radical for loss of a hydrogen atom. To calculate the bond dissociation energy, we have

a

group 1 group 2 group 3

group C/F/H2/O C/F2/H/O C/F3/O O/C/H

RH → R• + H 7007


Article

The Journal of Physical Chemistry A Table 14. Standard Entropy and Heat Capacities for Groups C/F/H2/O C/F2/H/O C/F3/O O/CH2F/O O/CHF2/O O/CF3/O O/C/Hb O/H/Ob a

S°298a

Cp300a

Cp400

Cp500

Cp600

Cp800

Cp1000

Cp1500

33.97 39.80 42.97 9.21 8.79 9.25 29.07 27.83

8.09 11.74 12.25 4.75 2.47 3.68 4.30 5.21

10.36 14.44 14.90 4.26 2.08 3.99 4.50 5.72

12.26 16.10 16.75 4.13 2.28 4.25 4.82 6.17

13.67 17.05 17.95 4.17 2.65 4.39 5.23 6.66

15.57 18.08 19.28 4.72 3.66 4.81 6.02 7.15

16.87 18.77 19.98 4.99 4.13 4.89 6.61 7.61

18.97 20.01 20.92 4.93 4.34 4.63 7.44 8.43

Units in cal mol−1 K−1. bBenson.35

Table 15. Recommended Hydrogen Bond Increment Group Values for Fluoro Methyl Hydroperoxy Radicals ΔCp(T), cal mol−1 K−1 group •

CH2FOO CHF2OO• CF3OO• a

ΔfH°298(HBI),a kcal mol−1

ΔS°298 (HBI), cal mol−1 K−1

300 K

400 K

500 K

600 K

800 K

1000 K

1500 K

90.9 91.0 91.9

0.32 −1.22 −1.13

−3.61 −2.97 −1.90

−3.64 −2.95 −2.56

−3.78 −3.02 −3.05

−3.97 −3.14 −3.39

−4.33 −3.42 −3.74

−4.58 −3.66 −3.93

−4.87 −4.12 −4.25

Equals the bond dissociation energy of CH3−xFxOO---H.

Cp(T) for a free radical formed via the elimination of H atom from its parent molecule. The symmetry of the parent compounds used to generate the groups is not included in the calculation of the HBI groups as group additivity was developed by Benson,35 and they are termed “intrinsic groups”. The symmetry of the radical needs to be included in the compilation of each target radical. Table 15 lists the hydrogen bond increment group values, standard enthalpies of formation, standard entropies, and heat capacities for fluorinated hydroperoxy radicals.

Δrxn H °298 = Δf H °298(R•) + Δf H °298(H) − Δf H °298(RH) = BDE (R−H)

Then, the enthalpy of formation of the radical can be written as Δf H °298(R•) = BDE (R−H) + Δf H °298(RH) − Δf H °298(H)

Here, the ΔfH°298(H) = 52.1 kcal mol−1 in the literature.15 Then, Δf H °298(R•) = BDE (R−H) + Δf H °298(RH) − 52.1 kcal mol−1

■

The HBI group allows one to calculate the ΔfH°298(R•) if one knows the ΔfH°298(RH) and the bond strength for the R---H bond being broken to form the radical and H atom. Values of bond dissociation energies for the corresponding radicals are from Table 12 in this study. The molecular structure of a radical (R•) is similar to that of the corresponding stable molecule (RH). It corresponds to the parent molecule minus a hydrogen atom at the carbon or oxygen site and to the atom sequence and chemical bonds in the parent molecule. If the differences in molecular structure and properties for R• and RH are properly calculated, one can calculate the ΔS°298, and ΔCp(T) values for R• from properties of the corresponding RH parent plus increment values for ΔS°298 and ΔCp(T) that account for these changes:

SUMMARY

Standard enthalpies of formation of fluoromethyl hydroperoxide, CH3−xFxOOH (1 ≤ x ≤ 3), fluoromethyl hydroperoxy radicals, CH3−xFxOO• (1 ≤ x ≤ 3), fluoromethyl-alkoxy radicals CH3−xFxO• and fluoromethyl-alcohols, CH3−xFxOH are determined by CBS-QB3, CBS-APNO, and G4 methods. Small standard deviations suggest good error cancellation of work reactions and accuracy. Standard entropy and heat capacity as a function of temperature are determined with B3LYP/6-31+G(d,p) optimized structures and frequencies. Internal rotors have been investigated by intramolecular torsion potential curves at the B3LYP/6-31+G(d,p) level. Bond dissociation energies for R−OOH, RO−OH, ROO−H, R−OO•, RO−O•, R−OH, RO−H, R−O•, and R−H have been determined and compared with literature. Addition of fluorine(s) to the carbon tends to increase the carbon−oxygen, the oxygen−oxygen, and the oxygen−hydrogen bond dissociation energies in the fluoroperoxides and alcohols. Hydrogen bond increments (HBI’s) have been developed for the fluorinated peroxides, alcohols, and peroxy and alkoxy radicals. Group additivity values for fluorinated methanols and methyl hydroperoxides are developed and fluorine/oxygen interaction terms are needed to calculate the thermochemical effects that fluorines have on the peroxide oxygen systems. These interaction groups, F/OO, F2/OO, and F3/OO and hydrogen bond increment groups CH2FOO•, CHF2OO•, and CF3OO• have been determined for the fluoro hydroperoxides and corresponding radicals.

Sint°298(R•) = S°298(RH) + ΔS°298 Cp(T )(R•) = Cp(T )(RH) + ΔCp(T )

Here, Sint° represents intrinsic entropy (excluding symmetry). Then, the increment values can be written as ΔS°298(HBI) = S°298(R•) − S°298(RH) ΔCp(T )(HBI) = Cp(T )(R•) − Cp(T )(RH)

These ΔS°298 and ΔCp(T) (300 ≤ T/K ≤ 1500) increments are group values for estimating the corresponding properties of the radical resulting from loss of a H atom from the parent and are termed hydrogen bond increments (ΔS°298(HBI)) and ΔCp(T)(HBI)). They are then used to calculate S°298 and 7008


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(15) Ruscic, B. Active Thermochemical Tables: Sequential Bond Dissociation Enthalpies of Methane, Ethane, and Methanol and the Related Thermochemistry. J. Phys. Chem. A 2015, 119, 7810−7837. (16) Burke, S. M.; Simmie, J. M.; Curran, H. J. Critical Evaluation of Thermochemical Properties of C1−C4 Species: Updated GroupContributions to Estimate Thermochemical Properties. J. Phys. Chem. Ref. Data 2015, 44, 013101. (17) Chase, M. W. J. NIST-JANAF Thermochemical Tables. J. Phys. Chem. Ref. Data. 1998, Monograph 9, 1−1951. (18) Luo, X.; Fleming, P. R.; Rizzo, T. R. Vibrational Overtone Spectroscopy of the 4νOH+νOH′ Combination Level of HOOH via Sequential Local Mode−local Mode Excitation. J. Chem. Phys. 1992, 96, 5659−5667. (19) Bodi, A.; Kercher, J. P.; Bond, C.; Meteesatien, P.; Sztáray, B.; Baer, T. Photoion Photoelectron Coincidence Spectroscopy of Primary Amines RCH2NH2 (R = H, CH3, C2H5, C3H7, i-C3H7): Alkylamine and Alkyl Radical Heats of Formation by Isodesmic Reaction Networks. J. Phys. Chem. A 2006, 110, 13425−13433. (20) Ruscic, B., Active Thermochemical Tables Enthalpies−Version 1.118 of the Thermochemical Network, available at http://ATcT.anl. gov, accessed April 24th 2016; see also: Ruscic, B.; Pinzon, R. E.; Morton, M. L.; von Laszewski, G.; Bittner, S. J.; Nijsure, S. G.; Amin, K. A.; Minkoff, M.; Wagner, A. F. Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 2004, 108, 9979−9997. and: Ruscic, B.; Pinzon, R. E.; von Laszewski, G.; Kodeboyina, D.; Burcat, A.; Leahy, D.; Montoya, D.; Wagner, A. F. Active Thermochemical Tables: Thermochemistry for the 21st Century. J. Phys.: Conf. Ser. 2005, 16, 561−570. (21) Csontos, J.; Rolik, Z.; Das, S.; Kállay, M. High-Accuracy Thermochemistry of Atmospherically Important Fluorinated and Chlorinated Methane Derivatives. J. Phys. Chem. A 2010, 114, 13093−13103. (22) NIST Computational Chemistry Comparison and Benchmark Database. NIST Standard Reference Database Number 101, Release 16a; Johnson, R. D., III, Ed.; NIST: Gaithersburg, MD, 2013. (23) Becke, A. D. Density-functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648−5652. (24) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti Correlation-energy Formula into A Functional of the Electron Density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789. (25) Sheng, C. Elementary, Pressure Dependent Model for Combustion of C1, C2 and Nitrogen Containing Hydrocarbons: Operation of A Pilot Scale Incinerator and Model Comparison. Ph.D. dissertation; New Jersey Institute of Technology, 2002. (26) Lay, T. H.; Krasnoperov, L. N.; Venanzi, C. A.; Bozzelli, J. W.; Shokhirev, N. V. Ab Initio Study of α-Chlorinated Ethyl Hydroperoxides CH3CH2OOH, CH3CHClOOH, and CH3CCl2OOH: Conformational Analysis, Internal Rotation Barriers, Vibrational Frequencies, and Thermodynamic Properties. J. Phys. Chem. 1996, 100, 8240−8249. (27) Batt, L.; Walsh, R. A Reexamination of the Pyrolysis of Bis Trifluoromethyl Peroxide. Int. J. Chem. Kinet. 1982, 14, 933−944. (28) Sun, H.; Bozzelli, J. W. Structures, Rotational Barriers, Thermochemical Properties, and Additivity Groups for 2-Propanol, 2-Chloro-2-propanol and the Corresponding Alkoxy and Hydroxyalkyl Radicals. J. Phys. Chem. A 2002, 106, 3947−3956. (29) Sun, H.; Bozzelli, J. W. Structures, Rotational Barriers, and Thermochemical Properties of β-Chlorinated Ethyl Hydroperoxides. J. Phys. Chem. A 2003, 107, 1018−1024. (30) Sun, H.; Chen, C.-J.; Bozzelli, J. W. Structures, Intramolecular Rotation Barriers, and Thermodynamic Properties (Enthalpies, Entropies and Heat Capacities) of Chlorinated Methyl Hydroperoxides (CH2ClOOH, CHCl2OOH, and CCl3OOH). J. Phys. Chem. A 2000, 104, 8270−8282. (31) Yamada, T.; Bozzelli, J. W. Thermodynamic Properties ΔHf°298, S°298, and Cp(T) for 2-Fluoro-2-Methylpropane, ΔHf°298 of Fluorinated Ethanes, and Group Additivity for Fluoroalkanes. J. Phys. Chem. A 1999, 103, 7373−7379.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpca.6b05293. Cartesian coordinates, frequencies, moments of inertia, optimized geometries, molecular structures, bond dissociation energy equations, explanation of “SMCPS” and “Rotator” and list of ten-parameter Fourier series functions, and group additivity calculation details (PDF)

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AUTHOR INFORMATION

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS The authors thank the editor and reviewers for their valuable suggestions and comments. REFERENCES

(1) Schneider, W. F.; Wallington, T. J. Ab Initio Investigation of the Heats of Formation of Several Trifluoromethyl Compounds. J. Phys. Chem. 1993, 97, 12783−12788. (2) Sawada, H. Fluorinated Peroxides. Chem. Rev. 1996, 96, 1779− 1808. (3) Hayman, G. D.; Derwent, R. G. Atmospheric Chemical Reactivity and Ozone-Forming Potentials of Potential CFC Replacements. Environ. Sci. Technol. 1997, 31, 327−336. (4) El-Taher, S. Ab Initio and DFT Investigation of Fluorinated Methyl Hydroperoxides: Structures, Rotational Barriers, and Thermochemical Properties. J. Fluorine Chem. 2006, 127, 54−62. (5) Reints, W.; Pratt, D. A.; Korth, H.-G.; Mulder, P. O−O Bond Dissociation Enthalpy in Di(trifluoromethyl) Peroxide (CF3OOCF3) as Determined by Very Low Pressure Pyrolysis. Density Functional Theory Computations on O−O and O−H Bonds in (Fluorinated) Derivatives. J. Phys. Chem. A 2000, 104, 10713−10720. (6) Harvey, J.; Tuckett, R. P.; Bodi, A. A Halomethane Thermochemical Network from iPEPICO Experiments and Quantum Chemical Calculations. J. Phys. Chem. A 2012, 116, 9696−9705. (7) Kosmas, A. M.; Mpellos, C.; Salta, Z.; Drougas, E. Structural and Heat of Formation Studies of Halogenated Methyl Hydro-peroxides. Chem. Phys. 2010, 371, 36−42. (8) Wang, H.; Bozzelli, J. W. Thermochemical Properties (ΔfH°(298 K), S°(298 K), Cp(T)) and Bond Dissociation Energies for C1−C4 Normal Hydroperoxides and Peroxy Radicals. J. Chem. Eng. Data 2016, 61, 1836−1849. (9) Wang, H.; Castillo, Á .; Bozzelli, J. W. Thermochemical Properties Enthalpy, Entropy, and Heat Capacity of C1−C4 Fluorinated Hydrocarbons: Fluorocarbon Group Additivity. J. Phys. Chem. A 2015, 119, 8202−8215. (10) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et al. Gaussian 09; Gaussian, Inc.: Wallingford, CT, 2009. (11) Curtiss, L. A.; Redfern, P. C.; Raghavachari, K. Gaussian-4 Theory. J. Chem. Phys. 2007, 126, 084108. (12) Montgomery, J. A.; Frisch, M. J.; Ochterski, J. W.; Petersson, G. A. A Complete Basis Set Model Chemistry. VII. Use of the Minimum Population Localization Method. J. Chem. Phys. 2000, 112, 6532− 6542. (13) Ochterski, J. W.; Petersson, G. A.; Montgomery, J. A. A Complete Basis Set Model Chemistry. V. Extensions to Six or More Heavy Atoms. J. Chem. Phys. 1996, 104, 2598−2619. (14) Wang, H.; Bozzelli, J. W. Thermochemistry and Kinetic Analysis on Unimolecular Dissociation Reaction of Oxiranyl Radical: A Theoretical Study. ChemPhysChem 2016, 17, 1983−1992. 7009


Article

The Journal of Physical Chemistry A (32) Yamada, T.; Lay, T. H.; Bozzelli, J. W. Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°298 and Cp(T)’s (300 < T/K < 1500): Group Additivity for Fluoroethanes. J. Phys. Chem. A 1998, 102, 7286−7293. (33) Huey, L. G.; Dunlea, E. J.; Howard, C. J. Gas-Phase Acidity of CF3OH. J. Phys. Chem. 1996, 100, 6504−6508. (34) Asher, R. L.; Appelman, E. H.; Tilson, J. L.; Litorja, M.; Berkowitz, J.; Ruscic, B. A Photoionization Study of Trifluoromethanol, CF3OH, Trifluoromethyl Hypofluorite, CF3OF, and Trifluoromethyl Hypochlorite, CF3OCl. J. Chem. Phys. 1997, 106, 9111−9121. (35) Benson, S. W. Thermochemical Kinetics; Wiley-Interscience: New York, 1976. (36) Cohen, N. Revised Group Additivity Values for Enthalpies of Formation (at 298 K) of Carbon−Hydrogen and Carbon−Hydrogen−Oxygen Compounds. J. Phys. Chem. Ref. Data 1996, 25, 1411− 1481. (37) Lay, T. H.; Bozzelli, J. W.; Dean, A. M.; Ritter, E. R. Hydrogen Atom Bond Increments for Calculation of Thermodynamic Properties of Hydrocarbon Radical Species. J. Phys. Chem. 1995, 99, 14514− 14527.

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