Ab-initio study of the energetics and thermodynamics of the reaction CH3H + O(3P) → CF3H … O → CF3 + OH

Ab-initio computations at 298.15 K were made of the activation quantities ΔH‡, ΔS‡, and ΔG‡ and of the reaction quantities ΔHr and ΔSr for CF3H + O(3P) → CF3H … O → .CF3 .OH. CF3H … O is the transition state (TS). GAUSSIAN92 was used and energies computed at a slightly modified Gaussian-2 level. Two potential surfaces for the TS had symmetries 3A′ and 3A″. The two rate constants included a semi-classical, quantum-mechanical-tunneling transmission coefficient. The ab-initio ΔH‡ and ΔHr values were in excellent agreement (± 1 kcal/mol) with experiment; but the ΔS‡, ΔG‡, and ΔSr values yielded somewhat poorer agreement. Experimental and ab-initio structures were in excellent agreement.