Computational thermochemistry of hydrocarbons, oxygenates, cyclic alkanes, and furans

Fundamental thermochemical properties including enthalpies (ΔH°f 298), entropies (S° (T)), heat capacities (Cp(T)), and bond dissociation energies (BDEs) for several common and complex hydrocarbon fuel species are determined using computational chemical methods. ΔH° f 298 values are calculated using work reactions with the B3LY P (6-31 G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, and G3MP2B3 calculation methods. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated for contributions to entropies and heat capacities. Kinetic rate parameters are calculated for hydrogen abstraction and chemical activation reactions.Recommended ΔH° f 298 and carbon-hydrogen (C–H) BDEs for several normal and branched alkanes and ketones including corresponding radicals from loss of hydrogen atoms show strong comparisons to available literature values. Ketone C–H BDEs in the α position decrease by 6-9 kcal mol-1 with increasing substitution compared to normal alkane C–H BDEs. Group additivity (GA) and hydrogen-bond increment (HBI) values for these ketones are determined.Thermodynamic parameters for exo-tricyclo[5.2.1.02,6]decane (TCD), principle component of the hydrocarbon fuel JP-10, and its radicals, diradicals, and carbenes are determined. ΔH°f 298 for TCD is found to be -19.5 kcal mol-1 and used to calculate C–H and C–C BDEs for TCD radical, diradical, and carbene formations. Hydrogen abstraction reactions by a pool of radical species are analyzed using the modified Arrhenius equation for calculation of temperature-dependent rate constants.High-energy substituted furans created from sustainable biomass sources are of interest in biofuel production due to their high-energy density, and physical properties which are comparable to modern fuel blends. Methoxyfurans show strong furan ring C—H BDEs of 120 kcal mol-' with a decrease to 98 kcal mol-1 for the methoxy-methyl C—H bonds. 2-methylfuran hydroperoxide and alcohol species have over 40 kcal mol-1 ranges for the O—O BDEs and alcohol O—H BDEs. Oxidation of 2-methylfuran radical, at the furan carbon across from the methyl group, has a 50.6 kcal mol-1 well depth. Reaction pathways including abstractions, group transfers, dissociations, and radical peroxy oxygen additions are considered. Temperature- and pressure-dependent rate constants are calculated using quantum Rice-Ramsperger-Kassel analysis and master equation for falloff and stabilization.