A theoretical HSAB study of the acidity of carbon acids CH(3)Z

The gas-phase acidity of nine carbon acids of the form CH(3)Z (nitromethane , acetophenone, dimethylsulfone, acetaldehyde, butanone, acetone, methyl ac etate, acetonitrile and dimethylsulfoxide) was investigated, in the search of correlations with global and local HSAB properties, calculated at the 3- 21G, 6-31G* and 6-31+G(3df, 2p) levels. A reasonable correlation was obtain ed with the calculated ionization energies. Based on the obtained correlati on, the gasphase acidity of methyl thioacetate was estimated (DeltaG(o) = 1 476 kJ mol(-1)) as close to that of the most acidic member of the series, n itromethane. The nucleophilic Fukui functions of the hard and soft anionic centers in each base - CH(2)Z stabilized by direct conjugation were calcula ted, following two different approaches, and their ratios utilized to inter pret the shifts in acidity when the acids are transferred from gas-phase to aqueous solution.