SECTION I: Kinetics of HO2 Abstraction of H Atoms From Hydrocarbons
Structures, internal rotational barriers and ideal gas thermochemical properties, ΔH°f98 for representative series of transition states for abstraction of H atoms from primary, secondary and tertiary hydrocarbons by the HO2 radical, TC-HOOH (1), TCC-HOOH (2), TC2C-HOOH (3), TC3C-HOOH (4), TC2CC-HOOH (5), TC2CC-HOOHC (6) and TC3CCC-HOOH (7) are analyzed in this study. Molecular structures and vibrational frequencies are determined at the B3LYP/6-3111G(d,p) density functional level. The S°298 and Cp(T) values (300≤T/K≤1500) from vibrational, translational, and external rotational contributions are calculated using statistical mechanics based on the vibrational frequencies and structures obtained from the density functional study. Internal rotor contributions are included in the S and CP(T) values. ΔHt°,TS of the transition states are computed at the G3MP2 level. The forward and reverse rate constants are calculated for the transition state reactions (1) to (7). ΔHrxn of these paths are estimated. ΔHt°,TS of species 1, 2, 3, 4 and 5 are also calculated at CBS-Q//B3LYP/6-311G(d,p) level and compared with the G3MP2 results.
SECTION II: Thermochemical Properties, Enthalpy, Entropy and Heat Capacity (T) for Model Urethane Monomers and Corresponding Radicals.
Two separate model urethanes (carbamates), Ethyl N Ethyl carbamate [C-C-N-C(O)-OC-C] and N (n-propyl) methylcarbamate [C-C-C-N-C(O)-O-C] are utilized to investigate the thermochemical properties and bond energies in several model urethane monomers. Molecular structure, vibration frequencies, energies, enthalpies (ΔH°f(298)) and bond energies are determined for the molecules and radicals at the B3LYP/6-31 G(d,p) Density Functional Calculation Level. Entropy (SΔ(298)) and heat capacity CP(T) are determined from the above structures and vibration frequencies. Enthalpies of formation (ΔfH°f(298)) are estimated using total energies including zero point vibrational energy (ZPVE), thermal contributions for each species and the calculated ΔHrxn from isodesmic- working reactions. Bond energies are also calculated. The enthalpy values calculated at the B3LYP/6-31 G(d,p) level for C-C-N-C(O)-O-C-C and C-C-C-N-C(O)-O-C are -115.08 and -113.34 kcal/mol, respectively. Carbon and nitrogen - hydrogen bond energies, calculated in this study are: 453.2 (kJ.mol) for C-C-Nj-C(O)-O-C-C, 400.3 (kJ.mol) for C-Cj-N-C(O)-O-C-C, 430.1 (kJ.mol) for C-C-N-C(O)-O-C-C, 429.4 (kJ.mol) for C-C-NC(O)-O-Cj-C, 439.9 (kJ.mol) for C-C-N-C(O)-O-C-C~, 452.7 (kJ.mol) for C-C-C-NiC(O)-O-C, 401.7 (kJ.mol) for C-C-Cj-N-C(O)-O-C, where j represents the radical site
