Effect of substituents on reactivity in eliminations from carbanions in the systems G·[graphic omitted]HR·[graphic omitted]HR·Z, where G = PhSO₂, Bz, or CN and Z = OPh, OMe, SPh, or SO₂Ph have been determined.

β-Phenyl substitution greatly accelerates carbanion formation in nitriles but depresses that of ketones. Sulphones, except when both α- and β-phenyl groups are present, are insensitive. These markedly different effects of β-phenyl substitution in the three different systems are discussed in terms of steric interference with the formation of a planar carbanion.

α-Phenyl substitution slightly accelerates deprotonation of nitriles but depresses that of ketones and sulphones. Methyl substitution in sulphones at α or β positions slightly retards deprotonation.

Substrates with G = PhSO₂ or CN react by the (E₁cB)_R mechanism and phenyl and methyl substituents at α- or β-carbon atoms all accelerate expulsion of the leaving group to a small extent. The effects are generally smaller than those of the same substituents in concerted processes and it is concluded, in conformity with earlier work, that extension of the bond to the leaving group in the transition state is small.

Phenoxy-sulphones with both α- and β-phenyl substituents behave exceptionally. Interconversion of the erythro- and threo-isomers does not occur under the reaction conditions and deprotonation of the threo-isomer occurs much more slowly than in the erythro-isomer or the unsubstituted substrate. Expulsion of the leaving group from the derived carbanion, however, occurs more rapidly in the threo than in the erythro-isomer.