Kinetics of reaction of picryl bromide with substituted naphthoate ions

Abstract

Second-order rate constants have been measured for the reactions of picryl bromide with 6- and 4-substituted 1-naphthoate and 6-substituted 2-naphthoate ions in 80% methanol–water at several temperatures and activation parameters have been calculated. The Hammett equation applies very well to these reactions. The rate constants are correlated with the pK_a values of the corresponding naphthoic acids via the Brönsted equation giving a β value of 0.30 for the 1-series and 0.56 for the 2-series. Electron-withdrawing groups decrease and electron-donating groups increase the rate. A linear correlation between ΔH^‡ and ΔS^‡ is indicative of a single mechanism.