NMR spectra of molecules oriented in a lyotropic mesophase. II. Spectra of pyridine and pyridine N-oxide

Abstract

PMR spectra of pyridine and pyridine N-oxide are studied in a lyotropic mesophase formed by a 14:1:1:20 mixture (by weight) of sodium dodecyl sulphate, decanol, sodium sulphate, and heavy water. The geometry information and the order parameters are derived. The structural information for pyridine thus obtained is compared with that obtained from the studies in a thermotropic phase. Differences up to 2 % in the interproton distance ratios for pyridine in the lyotropic and thermotropic phases are observed. They may arise partly due to the hydrogen bonding between the nonbonded electrons of nitrogen in pyridine and the water molecules of the lyotropic mesophase. No structural data for pyridine N-oxide are available for comparison.

It is found that although the arrangement of protons in pyridine is very similar to that in pyridine N-oxide, their molecular orientations in the lyotropic mesophase are quite different. A comparison of the order parameters of the various axes under similar conditions in both the cases is made.