Bridgehead β-deuterium secondary kinetic isotope effect in the solvolysis of endo-norbornan-2-yl p-bromobenzenesuiphonate

Abstract

1-Deuterio- and 1,2-dideuterio-endo-norbornan-2-yl p-bromobenzenesulphonates have been prepared and the secondary deuterium kinetic isotope effects have been measured in 80% aqueous ethanol (k^H/k^D 1.000 and 1.191 respectively at 54.5°) and in buffered acetic acid (k^H/k^D 0.996 and 1.194 respectively at 64.7°). These results establish that, when a β-C–H (D) bond is orthogonal to the developing vacant orbital of an incipient carbonium ion being formed from a secondary alkyl arenesulphonate, virtually no kinetic isotope effect will be observed.