Primary deuterium isotope effect in the proton transfer reaction between ethyl bis-(4-nitrophenyl)acetate and tetramethylguanidine in tetrahydrofuran solvent

Abstract

The reaction between ethyl bis-(4-nitrophenyl)acetate and tetramethylguanidine in tetrahydrofuran solvent gives a coloured product which decomposes under the influence of light to 4,4′-dinitrobenzophenone. The formation of the coloured material has been shown to take place in two steps. It is concluded that the first, faster step, which shows a primary deuterium isotope effect, k_H/k_D 3.4 at 25 °C, is the proton transfer reaction yielding the carbanion of the substrate. A possible source of error in primary kinetic isotope effects is discussed.