ISOTOPE EFFECT STUDIES ON ELIMINATION REACTIONS: III. NITROGEN ISOTOPE EFFECTS IN THE E2 REACTION OF ETHYLTRIMETHYL-AMMONIUM AND 2-PHENYLETHYLTRIMETHYLAMMONIUM IONS

Abstract

Nitrogen isotope effects have been determined for the E2 reaction of two quaternary ammonium salts with ethoxide ion in ethanol. Ethyltrimethylammonium iodide gave k14/k15 values of 1.017 at 60° and 1.015 at 95°, while 2-phenylethyltrimethylammonium bromide gave 1.012 at 40° and 1.009 at 60°. These results and the β-deuterium isotope effects reported by others have been interpreted in terms of the relative extent of Cα—N+ and Cβ—H bond weakening in the transition states of the two reactions.