Reaction Pathways for Gas-Phase Hydrolysis of Formyl Compounds HXCO (X = H, F, and Cl)

Formation and decomposition of the adduct species CHX(OH)₂, where X = H, F, and Cl, have been studied by means of ab initio molecular orbital theory. Equilibrium geometries and transition structures have been fully optimized with 6-31G* and 6-311G** basis sets at the Hartree-Fock and second-order Møller-Plesset perturbation levels of theory. Heats of reaction and barrier heights have been computed with Møller-Plesset theory up to full fourth order using the 6-311++G** basis. Addition of H₂O to HXCO yields CHX(OH)₂ which then decomposes preferentially by 1,2-elimination of HX to give formic acid as a product. Other higher energy paths, including 1,2-elimination of H₂ and the involvement of carbene species, are of negligible significance.