The Kinetic Studies on Acid-catalyzed Etherification of 4-(m- or p-Substituted phenylazo)-1-naphthols

Abstract

The 4- (phenylazo) -1-naphthol [1] and its derivatives were easily etherified in the presence of sulfuric acid to form 1-methoxy-4- (phenylazo) naphthalene and its derivatives. The irreversible reactions were traced in terms of visible spectrophotometry. The rate equation was of first-order with respect to J. The Hammett plots of derivatives with electron releasing group and with electron-attracting group gave two straight lines with slopes + 2.58and +0.40, respectively. The isokinetic plots gave two straight lines similarly. The B-values were 430K and 396K for electron-releasing and attracting group, respectively.
A probable mechanism, that the rate-determining being the a dhesion of methanol on the protonated tautomer (I) in the case of the electron-releasing group and that the rate-determining being the deprotonation from methanol adhesive substance toward (I) and dehydration in the case of the electron-attracting group, was proposed and discussed.