Kinetics and mechanism for the H‐for‐X exchange process in the H + C6H5X reactions: A computational study

The addition of H atoms to benzene and toluene and subsequent transformations were investigated using high level ab initio and density functional theory methods. Molecular structures and vibrational frequencies calculated at the B3LYP/6-311++G(d,p) level of theory were used in combination with adjusted G2M energetic parameters for RRKM rate constant calculations. Standard heats of formation for cyclohexadienyl and cyclohexadienyl, 6-methyl radicals calculated through isodesmic reactions amounted to 49.5 ± 2 and 42.9 ± 3 kcal/mol, respectively. Rate constants for various elementary reactions involved in the H-for-X exchange (X = D, CH3) were calculated and closely correlated with the available experimental kinetic data. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 633–653, 2001

[1]  M. Quack,et al.  Excited vibrational states of benzene: High resolution FTIR spectra and analysis of some out-of-plane vibrational fundamentals of C6H5D , 1997 .

[2]  A. Cabana,et al.  The ν4 Vibration–Rotation Bands of C6H6 and C6D6: The Analysis of the Bands and the Determination of the Bond Lengths , 1974 .

[3]  R. Timmons,et al.  Kinetics and mechanism of the reaction of hydrogen and deuterium atoms with benzene and benzene‐d 6 , 1973 .

[4]  J. Troe,et al.  Thermodynamic properties of benzyl radicals: enthalpy of formation from toluene, benzyl iodide, and dibenzyl dissociation equilibria , 1990 .

[5]  J. Troe,et al.  Elementary Steps in the Pyrolysis of Toluene and Benzyl Radicals , 1991 .

[6]  Wing Tsang,et al.  Heats of Formation of Organic Free Radicals by Kinetic Methods , 1996 .

[7]  K. Morokuma,et al.  Theoretical Study of Potential Energy Surface and Thermal Rate Constants for the C6H5 + H2 and C6H6 + H Reactions , 1997 .

[8]  J. A. Manion,et al.  Rates and mechanisms of gas-phase desubstitution of hexadeuteriobenzene and benzene derivatives C6H5X, X = CH3, CF3, OH, Cl, and F, by H atoms between 898 and 1039 K , 1990 .

[9]  I. V. Tokmakov,et al.  Experimental and Theoretical Studies of the Reaction of the Phenyl Radical with Methane , 1999 .

[10]  R. R. Baldwin,et al.  Addition of benzene and toluene to slowly reacting mixtures of hydrogen and oxygen at 773K , 1988 .

[11]  S. Benson,et al.  Thermochemical Kinetics: Methods for the Estimation of Thermochemical Data and Rate Parameters , 1976 .

[12]  Kenneth S. Pitzer,et al.  Energy Levels and Thermodynamic Functions for Molecules with Internal Rotation I. Rigid Frame with Attached Tops , 1942 .

[13]  Axel D. Becke,et al.  Density-functional thermochemistry. I. The effect of the exchange-only gradient correction , 1992 .

[14]  J. Pedley.  Thermochemical data and structures of organic compounds , 1994 .

[15]  Martin Head-Gordon,et al.  Quadratic configuration interaction. A general technique for determining electron correlation energies , 1987 .

[16]  H. Melville,et al.  The kinetics of the interaction of atomic hydrogen with olefines VI. An extension of the method and application to substituted olefines and aromatics , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[17]  O. Horie,et al.  Effect of thermal activation on the reaction of toluene with hydrogen atoms , 1976 .

[18]  W. Tsang.  Thermodynamic and kinetic properties of the cyclohexadienyl radical , 1986 .

[19]  R. Bühler,et al.  Kinetics of the hydrogen atom reactions with benzene, cyclohexadiene and cyclohexene: hydrogenation mechanism and ring cleavage , 1975 .

[20]  Masao Kimura,et al.  Molecular structure of benzene , 1976 .

[21]  L. Radom,et al.  Slow convergence of the møller-plesset perturbation series: the dissociation energy of hydrogen cyanide and the electron affinity of the cyano radical , 1987 .

[22]  J. A. Manion,et al.  Gas-phase hydrogenolysis of polychlorobiphenyls. , 1985, Environmental science & technology.

[23]  A. Ravishankara,et al.  Reaction of hydrogen atom with benzene. Kinetics and mechanism , 1984 .

[24]  Alexander M. Mebel,et al.  MODIFICATION OF THE GAUSSIAN-2 THEORETICAL MODEL : THE USE OF COUPLED-CLUSTER ENERGIES, DENSITY-FUNCTIONAL GEOMETRIES, AND FREQUENCIES , 1995 .

[25]  G. B. Skinner,et al.  Formation of deuterium and hydrogen atoms in the pyrolysis of benzene-d6 and chlorobenzene behind shock waves , 1984 .

[26]  Branko S. Jursic,et al.  Computing Transition State Structures with Density Functional Theory Methods , 1996 .

[27]  Parr,et al.  Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. , 1988, Physical review. B, Condensed matter.

[28]  J. Draeger.  The methylbenzenes—I. Vapor-phase vibrational fundamentals, internal rotations and a modified valence force field , 1985 .

[29]  W. Roth,et al.  Die Berechnung von Resonanzenergien; das MM2ERW‐Kraftfeld , 1991 .

[30]  R. Bader,et al.  Properties of atoms in molecules: electrophilic aromatic substitution , 1989 .

[31]  C. Bock,et al.  Homodesmotic reactions for the assessment of stabilization energies in benzenoid and other conjugated cyclic hydrocarbons , 1976 .

[32]  D. James,et al.  Kinetic study of the cyclohexadienyl radical. Part 2.—Patterns of combination and disproportionation with the methyl, ethyl, sec-propyl and tert-butyl radicals , 1968 .

[33]  L. Radom,et al.  Molecular orbital theory of the electronic structure of organic compounds. XVI. Conformations and stabilities of substituted ethyl, propyl, and butyl cations , 1972 .

[34]  Jorge M. Seminario,et al.  Recent developments and applications of modern density functional theory , 1996 .

[35]  J. E. Bennett,et al.  Studies of radical–molecule reactions using a rotating cryostat. Reactions of hydrogen atoms with organic substrates at 77 K , 1973 .

[36]  C. Eckart.  The Penetration of a Potential Barrier by Electrons , 1930 .

[37]  J. Troe,et al.  Pulse radiolysis, flash-photolysis, and shock wave study of the recombination hydrogen atom + benzyl .fwdarw. toluene at 300 and 1300-1650 K , 1990 .

[38]  A. Becke.  Density-functional thermochemistry. III. The role of exact exchange , 1993 .

[39]  J. E. Boggs,et al.  The computed force constants and vibrational spectra of toluene , 1986, Journal of computational chemistry.

[40]  H. Wagner,et al.  Die Reaktionen von atomarem Wasserstoff mit Cyclohexen, Cyclohexadien‐1,3 und Benzol , 1975 .

[41]  W. Roth,et al.  Die Bildungsenthalpie des Allyl‐ und Methallyl‐Radikals , 1991 .

[42]  Kang Yang.  Free Radical Reactions Initiated by Ionizing Radiation. II. Rate Constants for Hydrogen Atom Addition Reactions with Mono-olefins, Butadiene and Benzene , 1962 .

[43]  H. Arai,et al.  Mechanism of Hydrogenolysis. II. A Molecular Orbitals Study of Hydrogenolysis of Toluene , 1970 .

[44]  D. Pratt,et al.  Toluene: Structure, dynamics, and barrier to methyl group rotation in its electronically excited state. A route to IVR , 2000 .

[45]  W. Tsang,et al.  Thermal decomposition of phenyl iodide and o-iodotoluene , 1986 .

[46]  G. Schaftenaar,et al.  Molden: a pre- and post-processing program for molecular and electronic structures* , 2000, J. Comput. Aided Mol. Des..

[47]  W. Tsang,et al.  Mechanism and rate of hydrogen atom attack on toluene at high temperatures , 1986 .

[48]  M. Sauer,et al.  Rate constants and transient spectra in the gas-phase reactions of hydrogen atoms. Substituents effects in monosubstituted benzenes , 1970 .

[49]  F. Markert,et al.  UV spectra and kinetics of radicals produced in the gas phase reactions of Cl, F and OH with toluene , 1993 .

[50]  J. M. Simoes,et al.  Energetics of organic free radicals , 1996 .

[51]  M. Sauer,et al.  Reactions of hydrogen atoms with benzene and toluene studied by pulsed radiolysis: reaction rate constants and transient spectra in the gas phase and aqueous solution , 1967 .

[52]  A. Becke.  Density-functional thermochemistry. II: The effect of the Perdew-Wang generalized-gradient correlation correction , 1992 .

[53]  K. Homann,et al.  J. A. Kerr and M. J. Parsonage: Evaluated Kinetic Data on Gas Phase Addition Reactions. Reactions of Atoms and Radicals with Alkenes, Alkynes and Aromatic Compounds. Butterworths, London 1972, 384 S., Preis: £12.00 , 1973, Berichte der Bunsengesellschaft für physikalische Chemie.

[54]  Raymond W. Walker,et al.  Evaluated kinetic data for combustion modelling supplement I , 1994 .