Kinetics of removal of the hydrogen-bonded proton from substituted 1-phenylazo-2-naphthols by hydroxide ion
Abstract
The effect of an intramolecular hydrogen bond on the rate coefficients and equilibrium constants for dissociation of a series of substituted 1-phenylazo-2-naphthols has been studied in basic solution. With an ionized 4-hydroxy substituent, the hydrogen bond is strong and leads to exceptionally low acidity (pK0 > 16) and to a half-life in the millisecond range for proton removal by hydroxide ion in 95%(v/v) Me2SO–H2O. The results are compared with those for other species in which hydroxy and azo groups are intramolecularly hydrogen-bonded.