Abstraction and addition reactions of four γ-lactones with H-atoms and methyl radicals

The five-membered cyclic esters, or γ-lactones, are promising candidates as biofuel additives and green solvent components. A comprehensive study of thermochemical and kinetic properties of γ-butyrolactone (GBL), γ-valerolactone (GVL), γ-caprolactone (GCL), and γ-heptalactone (GHL) has been conducted. The entropy, , specific heat, , enthalpy function, , and the enthalphy of formation at 298.15 K, , as well as the adiabatic ionization potential and single bond dissociation energies are reported. Bimolecular rate constants for the abstraction of H-atom by H^• and CH${}_3^{•}$ are presented on a per abstractable hydrogen basis; abstraction at the tertiary carbon site is consistently favored, while abstraction by CH${}_3^{•}$ lags behind H^•. Addition reactions of H^• and CH${}_3^{•}$ have high barriers and favor addition to the C-center.