Using secondary alpha deuterium kinetic isotope effects to determine the stereochemistry of an E2 reaction; the stereochemistry of the E2 reaction of1-chloro-2-phenylethane with potassium tert-butoxide in tert-butyl alcohol

Isotopic labelling studies have shown that the E2 reaction of 1-chloro-2-ph enylethane with potassium tert-butoxide in tert-butyl alcohol occurs via an anti-periplanar stereochemistry. This demonstrates that the different seco ndary alpha deuterium kinetic isotope effects found for the high and low ba se concentrations and in the presence of 18-crown-6 ether are because of ch anges in transition state structure that occur when the form of the reactin g base changes rather than to a change in the stereochemistry of the reacti on.