Hydration of the complex of 4-methylquinoline N-oxide with chloroacetic acid in benzene
Abstract
Vapour pressure osmometry (v.p.o.) and 1H n.m.r. measurements of the 4-methylquinoline N-oxide complex (B) with chloroacetic acid (HA) in benzene containing different amounts of water provide evidence for an interaction interpreted in terms of the overall equilibrium (BHA)2+ H2O [graphic omitted] BHA + BHA,H2O, equivalent to a system of two competing equilibria 2(BHA) [graphic omitted] (BHA)2 and BHA + H2O [graphic omitted] BHA,H2O. Quantitative treatment of the v.p.o. and n.m.r. data gave K1 1.78 ± 0.47 molal–1, K2 24.35 ± 7.57 molal–1, and K3 13.68 ± 4.89. The previously reported anomalously high value for the difference between the chemical shift of dimer (δd) and monomer (δm) was an effect of residual moisture. Instead, δd–δm= 0.95 p.p.m.