Effect of diffuse functions on the potential-energy surfaces of the alkylation reactions X–+ CH3F → XCH3+ F–(X = OH, CH3, H2CCHO)

Abstract

The alkylation processes of the reactions X^–+ CH₃F → XCH₃+ F^–, where X = OH, CH₃ and H₂CCHO, have been studied theoretically by means of 3–21 + G ab initio calculations. Transition states have been directly located. The use of a diffuse function-augmented basis set allows kinetically (O-alkylation) and thermodynamically (C-alkylation) controlled reactions of acetaldehyde enolate to be clearly separated. The changes of potential surfaces by the use of the 3–21 + G basis set instead of the 3–21G one are discussed, with special attention to the relevant modifications of transition structures. The influences of thermal corrections and electron correlation have also been considered.