Kinetic studies on the aminolysis of 1‐(trimethylsilyl)ethyl arenesulphonates in acetonitrile and methanol

Nucleophilic substitution reactions of 1‐(trimethylsilyl)ethyl arenesulphonates with anilines and benzylamines in acetonitrile and methanol at 65·0°C were studied. The cross‐interaction constants, ρXZ, between substituents in the nucleophile (X) and leaving group (Z) are relatively small (0·10 for XC 6 H 4 NH 2 in MeCN) but similar to those for other S N 2 processes at a secondary carbon atom. This provides further evidence for an approximately constant, loose S N 2 transition state at a secondary carbon regardless of the size of the C α substituent. The transition‐state variations with substituents X and Z are in accord with that expected from the positive ρXZ value observed: a stronger nucleophile and/or nucleofuge leads to an earlier transition state, i.e. a lower degree of bond making and breaking.