¹H and ¹³C NMR studies of the self‐association of chlorpromazine hydrochloride in aqueous solution

Abstract

Abstract The 1 H NMR spectrum of chlorpromazine hydrochloride was fully assigned at 400 MHz. Similarly, the 13 C NMR spectrum was assigned unambiguously using two‐dimensional NMR. Measurements of chemical shift as a function of concentration in D 2 O showed appreciable changes of shift of both protons and carbons which were apparent even at solution concentrations two orders of magnitude lower than the critical micelle concentration (CMC). The relative magnitude of the shifts of the aromatic protons and carbons on dilution below the CMC were compatible with vertical stacking of the molecules in an off‐set manner such that maximum overlap of the chlorinated rings occurred. Proton chemical shift data were interpreted using a stepwise association model to quantify the extent of association in the pre‐CMC region.