Substitution at saturated carbon. Part XIII. Steric effects in the substitution of tetra-alkyltin compounds by mercury(II) chloride in t-butyl alcohol and in acetonitrile

Abstract

Rate constants have been determined for the substitution of tetramethyl-, tetraethyl-, tetra-n-propyl-, tetraisopropyl-, tetra-n-butyl-, and tetraisobutyl-tin by mercury(II) chloride in solvents t-butyl alcohol and acetonitrile. With both solvents, the rate constants decrease markedly along the series R₄Sn = Me₄Sn Et₄Sn > Prⁿ₄Sn Buⁿ₄Sn > Buⁱ₄Sn Prⁱ₄Sn and thus give rise to the same steric sequence of reactivity found previously for the substitution of tetra-alkyltins by mercury(II) chloride in methanol and methanol–water mixtures. It is concluded that the above substitutions in solvents t-butyl alcohol and acetonitrile proceed by essentially the same mechanism as do the corresponding substitutions in solvents methanol and methanol–water, that is by the S_E2(open) mechanism of substitution at saturated carbon.