The logarithms of the relative rates of cleavage of RSiMe3 compounds [R = 1-indenyl, 9-fluorenyl, 9-(2-bromofluorenyl), 9-(2,7-dibromofluorenyl), PhCC, Ph3C, Ph2CH, p-PhC6H4CH2, and PhCH2] by aqueous methanolic alkali correlate linearly with the pK's of the corresponding hydrocarbons R–H over a pKa range of 22 units; the ratio of RH/RD products obtained in 1:1 MeOH–MeOD is thought to be equal to the deuterium isotope effect for interaction of the carbanion R– with methanol.