The primary hydrogen kinetic isotope effect in the elimination from 2-phenethyl systems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science with Honours in Chemistry at Massey University

Abstract

The primary kinetic isotope effects for the base-catalysed E2 elimination from a series of substituted 2-phenethyl bromides and 2-phenethyldimethylsulphonium bromides in dimethyl sulphoxide-water as solvent at 20° have been measured. A broad maximum in the isotope effect was observed for the 2-phenethyl bromides. The Hammett p value for each reaction series at 20° has also been determined and both were large and positive. Arrhenius plots using the kH/kD ratios for each of the p-MeO substituted compounds at 20°, 30° and 40° were carried out to determine the importance of proton tunnelling in these reactions. The usefulness of the primary Kinetic isotope effect as a measure of proton position in the E2 transition states for these reactions is discussed.