| Thermochemical properties, ΔfHo 298, So298, and Cpo(T) (5 ≤ T/K ≤ 6000), are determined using different ab initio and density functional theory methods for three chloromethyl radicals, CH 2Cl, CHCl2, CCl3, all chlorobenzenes from monochlorobenzene to hexachlorobenzene, and all chlorophenols from ortho-, meta-, para-chlorophenol to pentachlorophenol. The B3LYP/6-31G(d,p) method is used in the structure optimization. The B3LYP/6-311+G(3df,2p), QCISD(T)/6-31G(d,p), and CBS-Q methods are used in single point calculations of total electronic energies. Harmonic vibration frequencies are scaled for zero point energies and thermal corrections. Isodesmic reaction(s) are utilized at each calculation level to determine Δ fHo298, of each species. Contributions to So298 and Cpo(T) from translation, vibration, and external rotations are calculated using the rigid-rotor-harmonic-oscillator approximation. Hindered internal rotational contributions to entropies and heat capacities are calculated by summation over the energy levels obtained from direct diagonalizations of the Hamiltonian matrix of the internal rotation. The C–H and C–Cl bond energies in methyl chlorides are also calculated. Group values are derived for use of group additivity estimation for higher chlorinated or oxy-chlorinated molecules.; Trends of kinetic parameters are estimated for: (1) association reactions of chloromethyl radicals, (2) association reactions of Cl atom with chloroalkyl radicals, (3) addition reactions of chlorine atom with Cl + RX → HCl + R•X, Cl + R → HCl + R• (hydrocarbons only), and H + RCl → HCl + R• (or R•X).; Elementary reaction kinetic models for the thermal pyrolysis and oxidation of chloroform, 1,3-hexachlorobutadiene, and ortho-chlorophenol, are developed. Thermochemical properties, ΔfHo 298, So298, and Cpo(T), for reactants, intermediate species, and products are determined by ab initio or density functional theory when no literature are available, or from a modified group additivity. High-pressure limit rate constants are also calculated by ab initio or density functional theory or in some cases, or are estimated based on trends of chlorinated species when no literature data are available. Pressure and temperature dependent (1 atm Ar and 808–1073 K for chloroform, 1 atm air and 773–1373 K for 1,3-hexachlorobutadiene, 4% O2 in 1 atm He and 400–800 K for ortho-chlorophenol) mechanisms are constructed utilizing QRRK for k(E) with master equation for fall-off. The mechanisms are compared with corresponding experimental profiles, respectively. |
