The kinetics of the fast proton-transfer reactions between 2,4-dinitrophenol and some aliphatic amines in chlorobenzene solution

Abstract

The rates of the proton-transfer reactions of 2,4-dinitrophenol with mono-, di-, and tri-n-butylamine in chlorobenzene solution at room temperature have been measured by a microwave temperature-jump technique, which can be used down to half-times of about 1 µsec. The forward rate constants are 20 to 300 times smaller than the value for diffusion control, probably on account of a small but finite activation energy. The Brønsted plot is not linear, the rate constant for tri-n-butylamine being about three times lower than the expected value. This deviation from a linear free-energy relation is attributed to the steric effect of the n-butyl group.