KINETIC-STUDIES ON THE AMINOLYSIS OF 1-(TRIMETHYLSILYL)ETHYL ARENESULFONATES IN ACETONITRILE AND METHANOL

Nucleophilic substitution reactions of 1-(trimethylsilyl)ethyl arenesu lphonates with anilines and benzylamines in acetonitrile and methanol at 65.0-degrees-C were studied. The cross-interaction constants, rho(X Z), between substituents in the nucleophile (X) and leaving group (Z) are relatively small (0.10 for XC6H4NH2 in MeCN) but similar to those for other S(N)2 processes at 2 secondary carbon atom. This provides fu rther evidence for an approximately constant, loose S(N)2 transition s tate at a secondary carbon regardless of the size of the C(alpha) subs tituent. The transition-state variations with substituents X and Z are in accord with thal expected from the positive rho(XZ) value observed : a stronger nucleophile and/or nucleofuge leads to an earlier transit ion state, i.e. a lower degree of bond making and breaking.