Multinuclear nuclear magnetic resonance, studies of lead(II) soaps. Part 3.—Studies on the liquid phase with reference to the behaviour of the corresponding acids

Abstract

¹ H NMR spectra and longitudinal relaxation times have been measured for a number of even-chain-length lead(II) carboxylates and their corresponding acids in the liquid phase. Differences are observed, suggesting that aggregation occurs in the former case. Support for this comes from the greater spectral linewidths and shorter T₁ values observed in the molten carboxylates. From analysis of longitudinal and transverse proton-relaxation rates, estimates are made of aggregate correlation times. From studies of the ²⁰⁷Pb NMR longitudinal relaxation of molten lead(II) decanoate at various field strengths it is suggested that the dominant relaxation mechanism involves chemical shift anisotropy. Using this data, information on aggregate motion and size is also obtained. ¹³C NMR spectra and relaxation data have been studied for the lead(II) alkanoates and corresponding acids in the liquid phase and the results support the idea of the existence of aggregates. Studies of the longitudinal ¹³C relaxation of molten lead(II) octanoate at various magnetic field strengths provide further insight on these systems, and support the view that the liquid phase of the molten carboxylates consists of small aggregates.