Carbon acidity and ring strain: A hybrid HF-DFT approach (Becke3LYP/6-311++G**)

Hybrid HF-DFT calculations have been carried out on pairs of neutral molecules and their conjugated bases in order to determine their gas-phase acidities (Delta H values). Fifteen compounds have been calculated, both carbon acids (methane, ethane, ethene, ethyne, cyclopropane, cyclopropene, tetrahedrane, cubane, bicyclo[1.1.0]butane and bicyclo[1.1.1]pentane and reference compounds (hydrogen fluoride, hydrogen chloride, water, dihydrogen, hydrogen cyanide). The results are excellent and allow to discuss some topics like ring strain, carbon hybridization, aromaticity and topological analysis of the electron density. (C) 1997 Elsevier Science Ltd.