Proton transfer between carbon acids and methoxide: Studies in methanol, the gas phase and by Ab initio MO calculations

Article abstract of DOI:10.1002/bbpc.19981020341

A detailed mechanism that features hydrogen-bonded carbanions as well as free carbanions is presented for hydrogen transfer between carbon acids and methoxide ion in methanol. This is refined for several compounds by measuring their gas phase acidities, ΔG_Acid⁰ kcal/mol: C₆H₅CH(CF₃)₂ [335.3]; p-C₆H₄CHClCF₃ [337.4]; 9-phenylfluorene [335.6]; C₆F₅H [349.2]. Ab inilio molecular orbital calculations are reported to evaluate the stability of possible intermediates along the reaction pathway from 2-hydro-2-phenyl-perfluoropropane and methoxide ion to the carbanion and methanol. The intermediate, {C₆H₅C(CF₃)₂} ^-·HOCH₃, is 6.8 kcal/mol more stable than the separated species, {C₆H₅C(CF₃)₂}^- and CH3OH, and 43.2 kcal/rnol more stable than C₆H₅CH(CF₃)₂ and ^-OCH₃. WILEY-VCH Verlag GmbH, 1998.