Nuclear magnetic resonance chemical shifts for alcoholic and phenolic protons in dimethyl sulphoxide: utility as a structural parameter
Abstract
The n.m.r. spectra of various pyridyl alcohols and phenols were measured in dimethyl or [2H6]dimethyl sulphoxide. Pyridyl alcohols were classified into three categories on the basis of their n.m.r. behaviour. In cases in which the hydroxy-proton was sufficiently fixed in space through intermolecular hydrogen bonding with the solvent, the n.m.r. signal was a triplet due to coupling with the α-methylene group. The δOH value was found to be temperature dependent and to vary with change of the structural nature of hydroxy-group. Various types of intra- and intermolecular hydrogen bonding interactions are invoked for the elucidation of n.m.r. patterns. Several N-methylated pyridyl alcohols were subjected to n.m.r. investigation, but failed to provide well resolved n.m.r. patterns. The correlation between δOH and pKHA of the corresponding phosphates proved the reliability of δOH as a structural parameter for a linear free energy relationship study of phosphate hydrolysis.