A comprehensive theoretical examination of primary dissociation pathways of formic acid

Primary dissociation pathways have been investigated for formic acid by ab initio molecular orbital methods. Reactant, transition state, and products were fully optimized with unrestricted Hartree-Fock and unrestricted second-order Møller-Plesset wave functions. The activation energy for decarboxylation of formic acid (CO₂+H₂) is 65.2 kcal mol^-1, while that for the dehydration process (CO+H₂O) is 63.0 kcal mol^-1. These theoretical results suggest that the decarboxylation and dehydration processes are competitive. The activation energy barrier for isomerization of formic acid to yield dihydroxymethylene is 73.7 kcal mol^-1 and may be a competitive process. Free radical initiation processes are predicted to be minor.