The Production of Aliphatic and Aromatic Compounds, in the High

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A: Spectroscopy, Molecular Structure, and Quantum Chemistry

The Production of Aliphatic and Aromatic Compounds, in the High Temperature Decomposition of Propargyl Chloride. Single Pulse Shock Tube Experiments, Quantum Chemical Calculations and Computer Modeling Faina Dubnikova, Carmen Tamburu, and Assa Lifshitz J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.8b10515 • Publication Date (Web): 03 Jan 2019 Downloaded from http://pubs.acs.org on January 3, 2019

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The Journal of Physical Chemistry

The Production of Aliphatic and Aromatic Compounds, in the High Temperature Decomposition of Propargyl Chloride. Single Pulse Shock Tube Experiments, Quantum Chemical Calculations and Computer Modeling Faina Dubnikova, Carmen Tamburu and Assa Lifshitz* The Institute of Chemistry, Edmund J. Safra Campus, Giv’at Ram The Hebrew University of Jerusalem, Jerusalem 9190401, Israel *To whom correspondence should be addressed: E-mail: [email protected]

ABSTRACT The thermal reactions of propargyl chloride were studied behind reflected shock waves in a pressurized driver 2’’i.d. single-pulse shock tube over the temperature range 1000-1350 K, and pressure range behind the reflected shocks of 2-4 atm. Cooling rates were ~ 5105 K/s. The reflected shock temperatures were calculated from the extent of elimination of hydrofluoric acid (HF) from 1,1,1-trifluoroetane: 1,1,1trifluoroetane (TFE): → HF + 1,1-difluoroethylene (DFE), that was added in small concentration (0.1%) to the reaction mixture to serve as a chemical thermometer. For comparison, the shock temperatures were obtained also from the measured incident shock velocities, using the three conservation equations and the ideal gas equation of states. Fifteen stable reaction products, containing different numbers of carbon atoms (from two to nine), both aliphatic and aromatic, chain and cyclic, with and without chlorine resulting from the initial rupture of the CCl bond in propargyl chloride were identified. Based on the results of quantum chemical calculations that were carried out, a chemical kinetic scheme containing 63 elementary steps was constructed. Comparison of the curves that were calculated by using the kinetic scheme with the experimental results shows good agreement.

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I.

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INTRODUCTION

In the present study the homogeneous thermal decomposition at high temperatures of an important chorine molecule: propargyl chloride, CHCCH2Cl, in a single pulse shock tube is presented. A large number of decomposition products are obtained and their yields are determined and calculated. When various hydrocarbons are subjected to the conditions that prevail in combustion, in parallel to the oxidation processes, they undergo thermal decomposition and fragmentation that are independent of the presence of air. The study of these decompositions in the absence of air, or another oxidizer is thus essential to reveal the mechanism of the overall combustion process. There are several studies on propargyl chloride1-4 and, also propargyl bromide5-7 and some with propargyl iodide.8-10 Not all their findings are similar to the present work. The experiments were carried out either under different conditions of temperature and pressure, or used different additives (H2, Cl2, C6H6, HCl and others). An additional option is to obtain the propargyl radical (C3H3) from propyne.11 In addition to the propargyl radical resulting from a week C-Cl bond breaking, another radical, C3H2Cl is also presented in the reaction mixture to provide the formation of products containing chlorine. The attack of chlorine atom on the reactant producing C3H2Cl radical was studied theoretically by Hudgens and Gonzales.12 Both these resonance stabilized radicals C3H3 and C3H2Cl12-14 can produce aliphatic chain and aromatic hydrocarbons via recombination reactions and some additional isomerizations. The single pulse shock tube is an ideal tool for studying combustion processes at high temperatures, since it imitates perfectly the conditions that prevail in combustions namely, pressure, temperature and reaction dwell times that are typical parameters of combustion processes at high temperatures.15 There is one factor however, that impairs to some extent the study of the kinetics of chlorinated hydrocarbons. Not all the reaction products are available for calibration so that their gas chromatographic sensitivities have to be estimated. Although the estimates are quite reliable, they prevent accurate ACS Paragon Plus Environment

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3 determination of some of the product yields. An additional issue is the lack of available information on both Arrhenius parameters of the reactions and thermochemical data of the species involved, particularly of chlorinated free radicals. To overcome this issue, detailed quantum chemical calculations were carried out. On the basis of quantum chemical theory, thermochemical parameters for the reactant, products and intermediate species are calculated and presented. The data for some species were taken from thermochemical databases.16,17 Kinetic parameters, such as values of pre-exponential factors and energy

barriers are also calculated for each elementary step in the reaction pathways. Among the large variety of reaction steps responsible for the formation of fifteen main experimental products, only several are presented in the kinetic scheme. Those of them that do not provide a significant contribution were eliminated from the scheme, based on the sensitivity analyses. Computer modelling is carried out and a comparison between calculated and experimental mole percent is shown. Some products are presented as the sum of their isomers.

II.

EXPERIMENTAL

The thermal reactions of propargyl chloride (C3H3Cl) were studied behind reflected shock waves in a 2” i.d. single-pulse shock tube.18 In order to increase the vapor pressure of the reactants and products, the tube was heated and maintained at 170oC. The driven section was 4 m long and was divided in the middle by a 2” ball valve. The driver had a variable length up to a maximum of 2.7 m and could be varied in small steps in order to tune for the best cooling conditions. A 36-L dump tank was connected to the driven section near the diaphragm position to prevent reheating of the system by reflection of transmitted shocks. "Mylar" polyester films of various thicknesses were used as diaphragms to separate the driver from the driven section. Figure 1 shows a schematic diagram of the single pulse shock tube.



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Figure 1. A schematic view of a single pulse shock tube

The shock temperature was determined both by the use of a chemical thermometer and the measurement of the incident shock wave velocity.19 Figure 2a presents an example of a pressure record of the incident shock wave from which the temperature and the pressure behind the reflected shock were calculated, by solving the three conservation equations and the ideal gas equation of state. There was a good agreement between the two methods. Figure 2b presents an example of the pressure record showing the heating and the cooling process.

Figure 2a. A pressure record showing the incident shock wave.


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Figure 2b. A pressure record showing the heating and the cooling process

A reaction mixture of 0.5% C3H3Cl + 0.1% C2H3F3 in argon was introduced into the driven section between the ball valve and the end plate, and pure argon into the driven section between the diaphragm and the valve, including the dump tank (Figure 1). After firing a shock, gas samples were transferred directly from the end plate of the driven section into gas chromatographs for products identification and quantitative analysis.20 Two gas chromatograms at two different temperatures are shown in Figure 3.



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Figure 3. Gas chromatograms of a post shock mixture of 0.5% Propargyl Chloride in argon heated to 1286 K/1090K, taken on a 2-m Porapaq N column using FID. The red lines represent the chemical thermometer, 0.1% of 1,1,1-trifluoroethane.

The reactant propargyl chloride, listed as 98% pure, was obtained from Sigma-Aldrich. Argon, used as a diluent, and helium, that served as the driver gas, were obtained from Matheson and were listed as 99.995% pure. Trifluoroethane (C3H3F3), used as a chemical thermometer, was obtained also from Matheson, as 99.9% pure. Most of the products, used for calibration and identification, were obtained from either Sigma-Aldrich or Matheson and were listed as at least 97% pure. They were used without further purification. None of the stable decomposition products were observed in the analyses of the unshocked samples.

III. Methods of Calculations III.1. Quantum chemical calculations. DFT (density functional theory) calculations were performed to generate a database of different chemical structures and energies related to reactant, main products, and ACS Paragon Plus Environment

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7 intermediate species and their reaction parameters. As we dealt with large number of bimolecular reactions, we used a long range corrected functional CAM-B3LYP (hybrid exchange-correlation functional using the Coulomb-attenuating method)21 in conjunction with the Dunning correlation

consistent polarized valence double  cc-pVDZ basis set22. The energetics for local minima and transition states was recalculated using coupled cluster theory CCSD(T).23,24 Such combination of methods and basis set yields reliable results and is quite economic in computational time requirements for molecular systems as those discussed in this publication. All calculations were carried out using the Gaussian-09 package.25 The vibrational analysis of the structures was performed at the same level of theory to characterize the optimized structures as local minima or transition states. Relative energies include zeropoint energy corrections (ZPE) of the corresponding species. All the calculated frequencies, the zero point energies and the thermal energies correspond to harmonic approximation. Intrinsic reaction coordinates calculation using internal coordinates was performed to examine whether the considered transition states connect the expected reactants and products.

III.2. Rate constant calculations. Rate constants were calculated from transition state theory, using the relation: k =  (kT/h) exp(S#R) exp(-H#/RT)

(1)

where  is the degeneracy of the reaction coordinate and S#(T) and H#(T) are the temperature dependent entropy of activation and the energy barrier respectively. For unimolecular reactions, H = E, where

E is the energy difference between the transition state and the reactant. E is equal to E0total + Ethermal where E0total is obtained by taking the difference between the total energies of the transition state and the reactant and Ethermal is the difference between the thermal energies of these species. Based on quantum chemical calculations, values of pre-exponential factors and energy barriers could be calculated for each particular rate constant. Each rate constant was calculated using equation (1) at several temperatures in order

to

obtain

the

rate

constant

in

terms

A exp (-Ea/RT). ACS Paragon Plus Environment

of

an

Arrhenius

equation,


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III.3. Temperature calculation. Reflected shock temperatures were determined from the extent of the decomposition of 1,1,1-trifluoroethan to 1,1-difluoroethylene + HF that was added in small quantities to the reaction mixtures to serve as a chemical thermomether.19 The calculations were carried out using the relation T = (E/R) / ln 1 ln(1) At

(2)

where t is the reaction time, A (1014.85, s1) and E (310, J/K.mol) are the pre-exponential factor and the activation energy of the chemical thermometer reaction.  is the extent of decomposition defined as:  = [CH2=CF2]t /( [CH 2=CF2]t + [CH3CF3]t ) (3)

Density ratios behind the reflected shocks were calculated from the measured incident shock velocities using the three conservation equations and the ideal gas equation of state26 1

1 2

2

where m = gas mass, u = gas velocity,  = gas density, H = gas energy, P = gas pressure, T = gas temperature, R = universal gas constant; “1” indicates the values prior heating by the incident shock whereas while “2” indicates the values after the incident shock wave heating.

IV.

Evaluation of Product Concentrations

The concentrations of the reactant and measurements of the individual products behind the reflected shock waves were calculated from their GC peak areas.26 Gas chromatographic (GC) analyses were performed using both flame ionization (FID) and mass selective (MSD) detectors. ACS Paragon Plus Environment

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9 The reaction products were identified by GC-MSD analyses and were also compared with

mixtures of known compounds. The identification was based on NIST Mass Spec Data Center.27 The GC-MSD analyses were used also for separation of several compounds with close or identical retention times, as can be seen in Figure 3. In both MSD and FID chromatograms the specific sensitivities were considerate. In both FID and MSD analyses, 2m, 1/8in stainless steel Porapak N columns were used. The sensitivities of the products were obtained by analyzing prepared known mixtures of several products and the reactant both on GC-FID and GC-MSD. The obtained peaks were compared to the reactant and the known concentrations were also considered. For only two products (C4H4 and C4H2), that we could not obtain commercially, we analyzed a mixture of several isomers of C4Hn and extrapolated the results.

V. Results and Discussion The starting reactions in the decomposition of propargyl chloride are the formation of two types of radicals: C3H3 and C3H2Cl. The first one is formed via the dissociation of the weak CCl bond which is ~260 kJ/mol. The second one can be formed by two different reactions, 1. CH bond cleavage via the energy barrier of ~340 kJ/mol and 2. interaction of propargyl chloride with Cl atom, resulting in the formation of C3H2Cl and hydrogen chloride (Reactions 1-3 in Table 1). Thus, four different radicals C3H3, C3H2Cl, Cl and H, as the result of propargyl chloride decomposition are formed. A large variety of reactions involving these radicals is possible. Additionally, these radicals can interact with the reactant, products and other intermediate species, formed in the overall reaction. Here we present only the reactions that are significant in the formation of the main products, on the base of the sensitivity analyses. The parameters of the majority of the reactions presented in the kinetic scheme were calculated using quantum chemical calculations and are presented in Table 1. Some reactions were taken from the literature,28 some were estimated. The table contains 63 reactions and is divided in 11 groups,



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10 according to their function in the mechanism. The names used in Table 1 are explained in Table 2 that presents also the thermochemical parameters of the structures. Three groups of main products can be characterized to help further discussion:

1) containing 2, 3 or 4 carbon atoms: acetylene (C2H2), chloroacetylene (C2HCl), propyne (C3H4), diacetylene (C4H2) and vinylacetylene (C4H4), 2) containing six carbon atoms; benzene, mono- and dichlorobenzenes, benzyne and their aliphatic chain isomers, and 3) compounds, containing more than six carbon atoms – phenylacetylene (C8H6) and indene (C9H8).

V.A. Formation of aliphatic chain isomers and aromatic isomers of benzene and mono- and di-substituted benzene: C6H6, C6H5Cl and C6H4Cl2. C3H3 is a resonance-stabilized radical. It can be presented by two resonance structures CH2C≡CH and CH2=C=CH, similar to allene and propyne. Radical C3H2Cl, similar to C3H3, is a resonance hybrid of the CHClC≡CH and CHCl=C=CH structures.

The interaction between these radicals, via the

connection of these radicals in different position, forms a variety of species: C3H3 + C3H3  reactive aliphatic chain isomers C6H6



C3H2Cl + C3H2Cl  reactive aliphatic chain isomers C6H4Cl2



C3H3 + C3H2Cl  reactive aliphatic chain isomers C6H5Cl



These reactive isomers, via different isomerizations, produce both stable aliphatic chain isomers and aromatic isomers: benzene, chlorobenzene and dichlorobenzenes. Here only the isomers that produce the final products via reaction pathways that effect in large yield are discussed. V.A.1. Aliphatic chain isomers and aromatic isomer of C6H5Cl. Two examples of potential energy surfaces are presented to ease the understanding of the reaction details. They show the sequence of reaction steps, starting from the reactive aliphatic chain isomers, monochloride-I (Figure 4) and monochloride-III (Figure 5) and ending in both surfaces as aromatic C6H5Cl. The main discrepancy ACS Paragon Plus Environment

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11 between the two surfaces is the different pathways of aromatic cycle formation from the aliphatic cyclic isomers, namely, the cyclic-monochloride-I on the first surface and cyclic-monochloride-III on the second one. On the first surface (Figure 4), cyclic aliphatic isomer via two 1,2- H-atom migrations turns into aromatic chlorobenzene. On the second surface (Figure 5), the only transition state that is responsible for the H atom shift is 1,3- H-atom migration. This step proceeds via much higher energy barrier (245 Vs 183 kJ/mol) as calculated relative to stable aliphatic chain isomers.

Figure 4. Potential energy surface of the transformations in reactive aliphatic chain isomer of C6H5Cl (monochloride-I) to chlorobenzene (values for energy in kJ/mol). The kinetics modeling calculations show that in the low temperature range the stable aliphatic chain isomer is presented as sum of both monochloride-II and monochloride-IV. When the temperature is increasing, monochloride-IV is the only stable aliphatic chain isomer, while monochloride-II is turning into aromatic cycle. In the high temperature range, the concentration of the aliphatic chain isomer ACS Paragon Plus Environment


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12 decreases, while the concentration of the aromatic isomer increases. It means that also monochloride-IV turns into aromatic cycle particularly.

Figure 5. Potential energy surface of the transformations in reactive aliphatic chain isomer of C6H5Cl (monochloride-III) to chlorobenzene (values for energy in kJ/mol). All the reaction steps that are shown in the two potential energy surfaces are given in detail in the kinetic scheme as reactions 8-16 (Table 1). The accordance between of calculated and experimental yield of aliphatic and aromatic isomers of C6H5Cl is shown in Figure 6a and Figure 6b. The values are presented as mole percent from the initial concentration of propargyl chloride. It should be mentioned that several cis-trans isomerization reactions around single bonds that proceed via low energy barriers (20 kJ/mol and lower) are not presented in the potential energy surfaces and in the kinetic scheme since they do not effect on the results of kinetic modeling.


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13

aromatic chain

aliphatic

cyclic C 6H 4

C6H6

aromatic

aliphatic C6H4Cl2

aromatic

aliphatic C6H5Cl

C2H2

Diacetylene

Vinylacetylene

C2HCl

C6H5-CCH

C3 H 4

Indene

Figure 6a. Comparison of experimental and calculated yields of reaction products. The plots for the aliphatic products C6H6, C6H4, C6H4Cl2 and C6H5Cl are the sum of several aliphatic chain isomers. The plot for aromatic C6H4Cl2 represents the sum of ortho, meta and para isomers. The points represent the experimental results while the lines represent the results of the modeling.



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Total decomposition C3H3Cl

Figure 6b. Total decomposition of C3H3Cl. The points represent the experimental results while the lines represent the results of the modeling.

Table 3 brings together the structures and energetics of the important steps of the C6H5Cl formation (columns 1 and 2) discussed above: a) the transformation of the reactive chain isomers to the stable chain isomers, b) its further cyclization to the cyclic aliphatic isomers, and c) the final transformations toward the aromatic cycle. Columns 3 and 4 present similar reactions in C6H4Cl2 and columns 5 and 6 in C6H6. It allows comparing the features of the mechanisms of formation for these three pairs of products.

V.A.2. Aliphatic chain isomers and aromatic isomers of C6H4Cl2. The structures of the reactive aliphatic chain dichloride-I and dichloride-III (Table 3) that are formed as the result of the direct recombination of two C3H2Cl radicals are similar to the structures of monochlorides I and III. Both reactive isomers produce, via 1,3- or 1,5- Cl-atom migration, the same most stable aliphatic chain isomer, dichloride-II. Next, it can form the cyclic isomer (cyclic-dichloride-I). Thus, only the isomer dichlorideII, either presents the main stable aliphatic chain isomer or produces aromatic isomers of dichlorobenzene. All these reactions are given in Table 1 as reactions 17-25. ACS Paragon Plus Environment

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15 V.A.3. Aliphatic chain isomers and aromatic isomer of C6H6. Regarding the lowest energy

reaction pathways in the compounds of the general formula C6H6, the direct recombination of two C3H3 radical results in the reactive aliphatic chain isomer C6H6-I, which is similar to monochloride-III and dichloride-III (column 5, Table 3). The isomer C6H6-I, via 1,5-H atom migration, produces the more stable aliphatic chain isomer C6H6-II. Next, the isomer C6H6-II either forms cyclic-C6H6-I isomer via the cyclization reaction or forms the most stable aliphatic chain isomer C6H6-III via the rotation around the double bond. Thus, the competition between these two reactions gives the relation between benzene and its aliphatic chain isomers (reactions 27-32, Table 1). It should be mentioned that during the temperature increase, the concentration of the aromatic isomers is rising and the aliphatic isomers are decreasing in all the cases (Figure 6a).

V.B. Formation of additional main products In addition to the detail discussion in section A regarding the formation of six aliphatic chain and aromatic products, insight into important details of mechanism of other nine products formation is presented. It should help in understanding of the kinetic scheme analysis. V.B.1. Formation of 3-hexene-1,5-diyne and its cyclic isomer (benzyne) of formula C6H4. Chain isomer of C6H4 is the result of two consecutive steps of the weak C–Cl bonds breaking in the dichlorideI (line 18, Table 2), which is the reactive chain isomer of C6H4Cl2. It should be mentioned, that the same reactive isomer takes part also in the formation of stable aliphatic chain and aromatic isomers of C6H4Cl2 via isomerization reactions as is shown in part A. In the first step, radical C6H4Cl-I (line 27, Table 2) is produced by the Cl-atom ejection (reaction 33, Table 1). In the second step, after the breaking of the remaining C–Cl bond, the aliphatic chain isomer of C6H4 is formed (reaction 34, Table 1). Benzyne is formed by the cyclization of this chain isomer, followed by two 1,2-H-atom migrations toward the meta, para and then to the most stable ortho isomer of benzyne (reactions 35-37, Table 1).



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16 V.B.2. Formation of C2HCl (chloroacetylene) and C4H2 (diacetylene). The formation of both chloroacetylene C2HCl and the C4H3 radical, which is the precursor of diacetylene, proceeds via decomposition of the radical C6H4Cl-II (line 28, Table 2). The lowest energy path for this radical formation is the attachment of the Cl atom to the chain isomer of C6H4 (reaction 38, Table 1). The radical C4H3 forms diacetylene, after the H-atom ejection (reactions 39-40, Table 1).

V.B.3. Formation of C3H4 (propyne), C2H2 (acetylene) and C4H4 (vinylacetylene). Propyne, C3H4, can be formed via two pathways: an attachment of hydrogen atom to the initial radical C3H3 (reaction 42, Table 1) and the interaction of the C3H3 radical with the reactant, propargyl chloride, resulting in the formation of propyne and the C3H2Cl radical (reaction 43, Table 1). Acetylene is formed via the attachment of the hydrogen atom to the reactant, propargyl chloride. As a result, the radical C3H4Cl is formed, which breaks down into acetylene and chloro-methyl radical CH2Cl (reactions 46 and 47, Table 1). Further, CH2Cl takes part in the formation of vinylacetylene (C4H4) via the recombination reaction with C3H3 and followed by the decomposition (reactions 48 and 49, Table 1). V.B.4. Formation of phenylacetylene C8H6 and indene C9H8. Phenyl radical is required as a participant in the process of both phenylacetylene and indene formation. Phenyl is formed mainly, via Clatom ejection from chlorobenzene and its precursor cyclic-monochloride-II (reactions 51, 52, Table 1). Other two reactions that produce phenyl radical are the H-atom ejection from benzene (reaction 50, Table 1) and, vise versa, H-atom addition to benzyne, (reaction 53, Table 1). V.B.4.a. Formation of phenylacetylene. When phenyl radical is attached to acetylene or chloroacetylene, two new radicals are formed, PHAC-H (line 43, Table 2) containing an extra H-atom and, PHAC-Cl (line 44, Table 2) containing an extra Cl atom. The last step is the ejection of this extra atom (reactions 54-57, Table 1). V.B.4.b. Formation of indene. The recombination of two radicals, phenyl and C3H3, results in the formation of the molecule C9H8 (line 46, Table 2), which is an isomer of indene (reaction 58). In order to ACS Paragon Plus Environment

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17 form indene, the H-atom should be removed from the C-H group in the benzene ring, which is situated in

α-position to the C3H3 group. Thus, radical C9H7-I (line 47, Table 2) is formed. Another possibility to form this radical is the addition of radical C3H3 to benzyne (reaction 59, Table 1). The next step is a radical C9H7-II formation (line 48, Table 2) which is already the structure containing two conjugated rings. The H-atom addition proceeding by two different paths results in indene formation (reactions 60-63, Table 1).

VI.

Conclusion

The thermal decomposition of propargyl chloride was studied behind reflected shock waves in a pressurized driver single pulse shock tube. From the large variety of chemical reactions, only those were used in the kinetic scheme, whose existence are necessary to provide significant contribution. The final kinetic scheme presented here includes 63 elementary steps. The comparison between the curves that were calculated by computer modeling and the experimental results shows good agreement. Based on the complex of reactions presented in the kinetic scheme, the sequence of all the main products formation is summarized in the following scheme. In the scheme red color denotes radicals, blue color – cyclic products.



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Acknowledgment The authors wish to thank the Israel Science Foundation (ISF), (grand No 118/98) for financial support.


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19

Refences (1) Kern, R. D.; Chen, H.; Qin, Z.; Xie, K. Reactions of C3H3Cl with H2, C3H4, C2H2 and C2H4 Behind Reflected Shock Waves. In Shock Waves at Marseille, Proceedings of the International Symposium on Shock Waves, 19th, Marseille, July 26-30, 1993, 2, 113-218. Brun, R.; Dumitrescu, L. Z., Eds.; Springer: Berlin, 1995. (2) Kern, R.D.; Xie, K.; Chen, H. The Reactions of Propargyl Chloride and 1,5-Hexadiyne Behind Reflected Shock Waves. Abstracts of Papers, American Chemical Society, Division of Fuel Chemistry, 1991, 36, 1423-1432. New Orleans, LA, 1991. (3) Michael, J. V.; Kumaran, S. S. Thermal Decomposition Studies of Halogenated Organic Compounds. Combust. Sci. and Tech. 1998, 134, 31-44. (4) Kumaran, S. S.; Tilson, J. L.; Lim, K. P.; Michael, J. V.; Suslensky, A.; Lifshitz, A. Isomerization and Decomposition of Chloromethylacetylene. Israel J. Chem. 1996, 36, 223-232. (5) Deyerl, H. J.; Fishcer, I.; Chen, P. Photodissociation Dynamics of the Propargyl Radical. J. Chem. Phys. 1999, 111, 3441-3448. (6) Howe, P. T.; Fahr, A. Pressure and Temperature Effects on Product Channels of the Propargyl (HCCCH2) Combination Reaction and the Formation of the “First Ring” J. Phys. Chem. A, 2003, 107, 9603-9610. (7) Kern, R. D.; Chen, H.; Kiefer, J. H.; Mudipalli, P. S. Thermal Decomposition of Propargyl Bromide and the Subsequent Formation of Benzene. Combustion and Flame 1995, 100, 177-184. (8) Scherer, S.; Just, Th.; Frank, P. High-Temperature Investigations on Pyrolytic Reactions of Propargyl Radicals. Proc. Comb. Inst. 2000, 28, 1511–1518. (9) Fernandes, R. X.; Hippler, H.; Olzmann, M. Determination of the Rate Coefficient for the C3H3 + C3H3 Reaction at High Temperatures by Shock-Tube Investigations. Proc. Comb. Inst. 2005, 30, 10331038. (10) Tsang, W., Tranter, R. S.; Brezinsky, K. Isomeric Product Distributions from the Self-Reaction of Propargyl Radicals. J. Phys. Chem. A 2005, 109, 6056-6065. ACS Paragon Plus Environment


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Page 20 of 39

20 (11) Rosado-Reyes, C. M.; Manion, J. A.; Tsang W. Kinetics of the Thermal Reaction of H Atoms with Propyne. J. Phys. Chem. A 2010, 114, 5710–5717. (12) Hudgens, J.W.; Gonzales, C. Chlorination Chemistry 4. Ab Initio Study of the Addition, Metathesis and Isomerization Channels Governing the Reaction of Chlorine Atom with Propargyl Chloride. J. Phys. Chem. A 2002, 106, 6143-6153. (13) Singh, H. J.; Gour, N. K. Recombination of Propargyl Radicals to Form Benzene: A Computational Study. Indian J. Chem. B, 2010, 49, 1565-1570.

(14) Georgievskii, Y.; Miller, J.A.; Klippenstein, S.J. Association Rate Constants for Reactions between Resonance-Stabilized Radicals: C3H3 + C3H3, C3H3 +C3H5, and C3H5 +C3H5. Phys. Chem. Chem. Phys. 2007, 9, 4315-4331. (15) Glick, H. S.; Squire, W.; Hertzberg, A. A New Shock Tube Technique for the Study of High Temperature Gas Phase Reactions. Proc. Comb. Inst. 1955, 5, 393-402. (16) Goos, E.; Burcat, A.; Ruscic. B. Ideal Gas Thermochemical Database with Updates from Active Thermochemical Tables, ftp://ftp.technion.ac.il/pub/supported/aetdd/thermodynamics , (retrieved September 1, 2013) (17) Afeefy, H. Y.; Liebman, J. F.; Stein, S.E. Neutral Thermochemical Data. In NIST Chemistry WebBook; Linstrom P.J.; Mallard, W.G. Eds.; NIST Standard Reference Database Number 69; National Institute of Standards and Technology, Gaithersburg, MD, http://www.webbook.nist.gov/, (retrieved December 20, 2018).

(18) Lifshitz, A.; Carrol H. F., Bauer, S.H., Studies with a Single Pulse Shock Tube. II. The Thermal Decomposition of Perfluorocyclobutane. J. Chem. Phys. 1963, 39, 1661-1664. (19) Tsang, W.; Lifshitz, A. Kinetic Stability of 1,1,1-Trifluoroethane. Int. J. Chem. Kinet. 1998, 30, 621-628. (20) Lifshitz, A.; Bauer, S. H.; Resler, E. L. Studies with a Single Pulse Shock Tube. I. The Cis  Trans Isomerization of 2-Butene, J. Chem. Phys. 1963, 38, 2056-2063. ACS Paragon Plus Environment

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21 (21) Yanai, T.; Tew, D.; Handy, N. A New Hybrid Exchange–Correlation Functional Using the

Coulomb-Attenuating Method (CAM-B3LYP). Chem. Phys. Lett. 2004, 393, 51-57. (22) Dunning, T. H. Gaussian-Basis Sets for Use in Correlated Molecular Calculations. 1. The Atoms Boron through Neon and Hydrogen. J. Chem. Phys. 1989, 90, 1007-1023. (23) Purvis III, G. D.; Bartlett, R. J. A Full Coupled-Cluster Singles and Doubles Model – the Inclusion of Disconnected Triples. J. Chem. Phys. 1982, 76, 1910-1918. (24) Scuseria, G. E.; Schaefer, III, H. F. Is Coupled Cluster Singles and Doubles (CCSD) more Computationally Intensive than Quadratic Configuration-Interaction (QCISD). J. Chem. Phys. 1989, 90, 3700-3703. (25) Frisch, M. J.; Trucks, G.W.; Schelegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Peterson, G. A., et al. Gaussian 09, version B.01; Gaussian, Inc.; Wallingford, CT, 2009. (26) Lifshitz, A.; Agranat, A.; Bidani M.; Suslensky, A. Thermal Reactions of Pyrrolidine at Elevated Temperatures. Studies with a Single-Pulse Shock Tube. J. Phys. Chem. 1987, 91, 6043-6048. (27) Stein, S. E. Mass Spectra. In NIST Chemistry WebBook; Linstrom P.J.; Mallard, W.G. Eds.; NIST Standard Reference Database Number 69; National Institute of Standards and Technology, Gaithersburg, MD, http://www.webbook.nist.gov/, (retrieved December 20, 2018). (28) Manion, J. A.; Huie, R. E.; Levin, R. D.; Burgess Jr., D. R.; Orkin, V. L.; Tsang, W.; McGivern, W. S.; Hudgens, J. W.; Knyazev, V. D.; Atkinson, D. B. et al. NIST Chemical Kinetics Database, NIST Standard Reference Database Number 17; National Institute of Standards and Technology, Gaithersburg, MD, http://kinetics.nist.gov/, (retrieved September 2015).



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 39

22 Table 1. Kinetic Scheme of the Main Product Formation; Values for ΔSr and ΔHr at T = 1250 K No

A*

reaction

E≠ kJ/mol

ΔSr J/Kmol

ΔHr kJ/mol

ref.

Initiation steps of propargyl chloride decomposition. Production of C3H3 (r) and C3H2Cl (r) 5.00×1014 1 C3H3Cl → C3H3(r) + Cl(r) 238.5 135.9 259.5 est 2

C3H3Cl → C3H2Cl(r) + H(r)

1.50×1015

320.2

139.6

353.6

3

C3H3Cl + Cl(r) → C3H2Cl(r) + HCl

3.50×1010

5.0

36.4

88.3

4

Interactions between produced atomic radicals 315.1 103.0 HCl + Ar → H(r) + Cl(r) + Ar 1.82×1013

441.9

29

5

H2 + Ar → H(r) + H(r) + Ar

1.41×1013

424.4

115.5

447.4

29

6

Cl2 + Ar → Cl(r) + Cl(r) + Ar

1.00×1014

226.4

101.3

247.3

29

7

HCl + Cl(r) → Cl2 + H(r)

1.50×1015

199.2

0.8

194.6

29

8

Formation of C6H5Cl (chlorobenzene and its aliphatic chain isomers) (Figs. 4 and 5) 187.5 264.9 C3H3(r) + C3H2Cl(r) → monochloride-I 5.00×1012 0.0 est

9

monochloride-I → monochloride-II

2.76×1013

201.3

15.9

83.7

monochloride-II → cyclic-

2.62×1011

140.2

32.2

29.7

1.13×1014

154.0

14.6

61.5

5.03×1012

1.7

31.0

359.5

2.50×1011

0.0

179.1

285.4

1.42×1012

156.1

27.2

74.9

1.92×1011

178.3

28.5

54.0

1.30×1012

187.5

17.2

310.5

10

est

monochloride-I 11

cyclic-monochloride-I → cyclicmonochloride-II

12

cyclic-monochlorideII → chlorobenzene

13

C3H3(r) + C3H2Cl(r) → monochloride-III

14 monochloride-III → monochloride-IV 15

monochloride-IV→ cyclicmonochloride-III

16

cyclic-monochloride-III → chlorobenzene


est

Page 23 of 39 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


23 A*

E≠ kJ/mol

ΔSr J/Kmol

No

reaction

ΔHr kJ/mol

ref.

17

Formation of C6H4Cl2 (dichlorobenzenes and their aliphatic chain isomers) C3H2Cl(r) + C3H2Cl(r) → dichloride-I 0.0 179.1 276.6 2.00×1011

est

18

dichloride-I → dichloride-II

19

C3H2Cl(r) + C3H2Cl(r) → dichloride-III

1.13×1012

195.4

3.3

51.9

1.00×1012

0.0

186.2

247.8

20

dichloride-III → dichloride-II

2.21×1013

205.1

10.9

80.8

21

dichloride-II → cyclic-dichloride-I

6.66×1011

158.6

61.1

33.9

4.39×1013

50.6

9.6

31.8

3.08×1012

25.5

26.4

369.5

2.36×1012

42.7

26.4

372.9

9.37×1012

138.5

20.1

53.1

5.30×1012

6.3

38.5

385.9

22 23 24 25 26

cyclic-dichloride-I→cyclicdichloride-II cyclic-dichloride-II→ m-diclorobenzene cyclic-dichloride-II → p-diclorobenzene cyclic-dichloride-II→ cyclicdichloride-III cyclic-dichloride-III→ o-diclorobenzene

27

Formation of C6H6 (benzene and its aliphatic chain isomers) 181.2 262.0 C3H3(r) + C3H3(r) → C6H6-I 5.00×1011 0.0

38

C6H6-I → C6H6-II

2.18×1012

164.5

13.8

32.2

29

C6H6-II → cyclic-C6H6-I

7.08×1011

149.0

52.3

8.8

30

cyclic-C6H6-I → cyclic-C6H6-II

1.96×1013

136.4

22.6

50.2

31

cyclic-C6H6-I → benzene

1.20×1012

1.7

41.4

365.8

32

C6H6-II → C6H6-III

2.35×1013

193.8

13.8

20.1


est

The Journal of Physical Chemistry 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

24 A*

E≠ kJ/mol

Page 24 of 39

ΔSr J/Kmol

ΔHr kJ/mol

No

reaction

33 34

Formation of C6H4 (benzynes and their aliphatic chain isomers) from the reactive aliphatic isomer of C6H4Cl2 (dichloride-I) dichloride-I → C6H4Cl-I (r) + Cl(r) 198.8 132.7 222.6 2.50×1014 150.7 107.6 154.8 C6H4Cl-I(r) → C6H4 + Cl(r) 7.50×1014

35

C6H4 → p-benzyne

6.52×1011

111.7

49.4

5.0

36

p-benzyne → m-benzyne

2.88×1014

141.5

1.7

36.8

37

m-benzyne → o-benzyne

7.05×1013

235.6

1.3

77.8

38

Formation of C2HCl and C4H2 from aliphatic chain C6H4 and C6H4Cl (r) (continuation of reaction 33) 0.0 C6H4 + Cl(r) → C6H4Cl-II(r) 117.6 85.0 5.00×1013

39

C6H4Cl-II(r) → C2HCl + C4H3(r)

5.43×1015

166.1

112.2

157.8

40

C4H3 (r) → C4H2 + H(r)

1.13×1014

167.8

108.8

177.4

41

C2HCl + H(r) → C2H2 + Cl(r)

6.00×1012

25.9

37.7

98.8

42

Formation of C3H4, C2H2 and C4H4 from C3H3Cl and C3H3 (r) 0.0 C3H3(r) + H(r) → C3H4 145.2 382.5 1.14×1014

43

C3H3(r) + C3H3Cl → C3H4 + C3H2Cl(r)

2.00×1012

65.3

5.4

28.9

ref.

est 29

est

44

C3H4 + Cl(r) → C3H3(r) + HCl

5.00×1011

18.4

41.9

59.4

45

C3H4 + H(r) → C3H3(r) + H2

1.20×1014

4.2

29.3

64.4

46

C3H3Cl + H(r) → C3H4Cl(r)

1.00×1015

25.5

115.5

151.9

47

C3H4Cl(r)→ C2H2 + CH2Cl(r)

2.20×1015

145.2

162.4

97.9

48

C3H3(r) + CH2Cl(r) → C4H5Cl

1.00×1013

0.0

240.2

305.5

49

C4H5Cl → C4H4 + HCl

5.18×1013

197.1

180.8

21.3

50

C6H6 → Phenyl(r) + H(r)

Formation of phenyl radical 431.1 7.00×1015 C6H5Cl → Phenyl(r) + Cl(r) 400.1 3.00×1015

160.7

475.8

est

143.5

398.0

est

51 52 53

cyclic-monochloride-III → Phenyl (r) + Cl(r) Phenyl(r) → o-benzyne + H(r)

1.00×1015

75.3

126.4

87.5

4.28×1014

310.5

116.8

333.1


Page 25 of 39 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


25 A*

E≠ kJ/mol

ΔSr J/Kmol

ΔHr kJ/mol

No

reaction

54

Formation of phenyl acetylene from phenyl radical and C2H2 and C2HCl PHAC-H(r) → Phenyl(r) + C2H2 151.9 152.3 141.5 1.61×1016

55

PHAC-H(r) → PHAC + H(r)

2.23×1012

46.0

115.5

117.2

56

Phenyl(r) + C2HCl → PHAC-Cl(r)

4.00×1013

6.3

120.9

205.1

57

PHAC-Cl (r) → PHAC + Cl(r)

2.28×1013

42.3

122.2

82.4

58

Formation of indene through the addition of C3H3 (r) to phenyl and o-benzyne Phenyl(r) + C3H3(r) → C9H8 0.0 204.6 385.4 8.00×1011

59

C9H8 + Cl(r) → C9H7I(r) + HCl

1.00×1014

47.7

47.7

13.4

60

o-benzyne + C3H3(r) → C9H7-I(r)

1.00×1011

16.7

170.7

263.2

61

C9H7-I(r) → C9H7-II(r)

1.22×1012

69.5

43.5

50.2

62

C9H7-II(r) + H(r) → Indene

1.00×1014

0.0

136.4

530.2

1.00×1012

0.8

3.3

176.6

63

C9H7-II(r) + C3H3Cl → Indene + C3H2Cl(r)

*

ref.

est

A units are s-1 for unimolecular reactions and cm3 mol-1s-1 Abbreviation “est” denotes estimated in the “reference” column. The empty space in this column refers to our quantum chemical calculations.



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 39

26 Table 2. Calculated Thermodynamic Properties of Reactant, Products and Intermediates at 298 K N°

structure

Hf (kJ/mol)

S (kJ/K.mol)

204.2

289.5

reactant – propargyl chloride 1

C3H3Cl

ClH2C

C

CH

radicals, produced from reactant 2

C3H3 (radical)

338.9

259.0

3

C3H2Cl (radical)

328.4

294.6

products of total formula C6H5Cl 4

monochloride-II

294.6

361.9

5

monochloride-IV

294.6

359.0

8

chlorobenzene

259.0

312.5

reactive aliphatic chain isomers of total formula C6H5Cl monochloride-I

259.0

364.0

monochloride-III

259.0

372.4

intermediate cyclic aliphatic isomers of chlorobenzenes 9

cyclic-monochloride-I

350.6

327.6

10

cyclic-monochloride-II

411.3

340.6

11

cyclic-monochloride-III

363.2

328.4


Page 27 of 39 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


27

N°

structure

Hf (kJ/mol)

S (kJ/K.mol)

product of total formula C6H4Cl2 12

dichloride-II

324.7

411.3

13

m-dichlorobenzene

28.0

347.3

14

p-dichlorobenzene

24.7

347.7

15

o-dichlorobenzene

33.1

346.0

reactive aliphatic chain isomers of total formula C6H4Cl2 16

dichloride-I

404.6

398.7

17

dichloride III

375.7

406.3

intermediate cyclic aliphatic isomers of dichlorobenzene 18

cyclic-dichloride-I

362.3

357.7

19

cyclic-dichloride-II

392.5

365.3

20

cyclic-dichloride-III

414.6

377.0

384.1

328.9

products of total formula C6H6 21

C6H6-II



Page 28 of 39

28

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

N°

structure

Hf (kJ/mol)

S (kJ/K.mol)

22

C6H6-III

362.3

339.7

23

C6H6

82.8

268.6

reactive aliphatic chain isomers of total formula C6H6 24

C6H6-I

414.6

339.3

intermediate cyclic aliphatic isomers of benzene 25

cyclic-C6H6-I

398.3

287.4

26

cyclic-C6H6-II

448.5

310.0

intermediate chain aliphatic isomers of C6H4Cl 27

C6H4Cl-I (radical)

505.4

370.7

28

C6H4Cl-II (radical)

577.8

364.0

product of total formula C6H4 chain aliphatic isomer and cyclic isomers (benzynes) 29

C6H4

541.8

321.7

30

p-benzyne

553.5

286.6


Page 29 of 39 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


29

N°

structure

Hf (kJ/mol)

S (kJ/K.mol)

31

m-benzyne

516.3

287.9

32

o-benzyne

439.3

288.3

products containing 2, 3 and 4 carbon atoms 33

C3H4 (propyne)

185.4

248.5

34

C2H2 (acetylene)

227.2

200.8

35

C2HCl (chloroacetylene)

226.4

201.7

36

C4H2 (diacetylene)

459.8

256.1

37

C4H4 (vinylacetylene)

294.6

276.6

intermediate radicals containing 2, 3 and 4 carbon atoms 38

CH2Cl (radical)

148.1

259.8

39

C3H4Cl (radical)

277.4

301.7

40

C4H3 (radical)

515.5

281.2

41

C4H5Cl (radical)

177.8

321.3

product of total formula C6H5-CCH - phenylacetylene 42

PHAC

305.4

331.0

intermediate radicals for phenylacetylene formation

43

PHAC-H (radical)

415.9

347.3

44

PHAC-Cl (radical)

350.6

384.9



Page 30 of 39

30

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

Hf (kJ/mol) product of total formula C9H8 - indene

N°

45

structure

indene

S (kJ/K.mol)

161.1

331.8

intermediates for indene formation

46

C9H8

276.6

362.3

47

C9H7-I (radical)

508.4

368.6

48

C9H7-II (radical)

464.8

337.2


Page 31 of 39 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


Table 3. Main Structures from the Lowest Energy Reaction Paths of C6H6, C6H5Cl and C6H4C2 (Aliphatic Chain and Aromatic) Formation. The values for the energy barriers are in kJ/mol. C6H4Cl2 C6H6 C6H5Cl 1

2

3

4

5

6

Name of isomer

monochloride-I

monochloride-III

dichloride-I

dichloride-III

C6H6-I

Isomerization (first step of reaction)

1,3-migration of Cl

1,6-migration of H

1,3-migration of Cl

1,5-migration of Cl

1,5-migration of H

200

153.6

199.6

192.5

163.2

monochloride-II

monochloride-IV

dichloride-II

C6H6-II

C6H6-III

148.5

178.7

152.7

164.8

193.7*

cyclic monochloride-I

cyclic monochloride-III

cyclic dichloride-I

cyclic-C6H6-I

157.3

182.4

135.1

133.5

Structure of reactive aliphatic chain isomer

Barrier Structure of stable aliphatic chain isomer

Name of isomer Barrier of cyclization Structure of the first cyclic aliphatic isomer Name of isomer The highest barrier of further reorganization of cyclic aliphatic isomer to aromatic one

*Isomerization C6H6-II to C6H6-III



TOC Graphic


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Figure 1. A schematic view of a single pulse shock tube



Figure 2a. A pressure record showing the incident shock wave.

Figure 2b. A pressure record showing the heating and the cooling process


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Figure 3. Gas chromatograms of a post shock mixture of 0.5% Propargyl Chloride in argon heated to 1286 K/1090K, taken on a 2-m Porapaq N column using FID. The red lines represent the chemical thermometer, 0.1% of 1,1,1-trifluoroethane.



Figure 4. Potential energy surface of the transformations in reactive aliphatic chain isomer of C 6H5Cl (monochloride-I) to chlorobenzene (values for energy in kJ/mol).


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Figure 5. Potential energy surface of the transformations in reactive aliphatic chain isomer of C 6H5Cl (monochloride-III) to chlorobenzene (values for energy in kJ/mol).



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Figure 6a. Comparison of the experimental and the calculated yields of the reaction products. The plots for the aliphatic products C6H6, C6H4, C6H4Cl2 and C6H5Cl represent the sum of several aliphatic chain isomers. The plot for aromatic C6H4Cl2 represents the sum of ortho, meta and para isomers. The points represent the experimental results while the lines represent the results of the modeling. ACS Paragon Plus Environment

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Figure 6b. Total decomposition of C3H3Cl. The points represent the experimental results while the line represents the results of the modeling.


The Production of Aliphatic and Aromatic Compounds, in the High

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