Theoretical studies on the thermochemistry of stable closed-shell C1 and C2 brominated hydrocarbons

摘要

The enthalpies of formation of stable closed shell C1 and C2 brominated hydrocarbons have been predicted using Gaussian-3X model chemistry. The entropy, heat capacity, and thermal corrections are calculated from B3LYP/6-31G(2df,p) geometries and vibrational frequencies using rigid-rotor-harmonic-oscillator approximation, except for the quantities of the internal rotations in ethanes, which are calculated using the quantum-mechanical energy levels. Enthalpies of formation have been obtained from G3X atomization and isodesmic reactions. Good agreement is observed on the well-established experimental enthalpies of formation of CH3Br, CH2Br2, CH2CIBr, and C2H3Br from the high-resolution threshold photoelectron photoionization coincidence study.