Proton spin–lattice relaxation in acetylthiocholine, butyrylcholine and carbamylcholine halides

Abstract

Spin–lattice relaxation times (T₁) of protons in polycrystalline acetylthiocholine chloride, acetylthiocholine iodide, butyrylcholine chloride, butyrylthiocholine iodide and carbamylcholine chloride have been measured over a range of temperatures by pulsed proton magnetic resonance. For all the compounds double minima were observed in T₁, and the results have been interpreted by considering the methyl-group reorientations about the C₃ axis and the role of spin diffusion of other protons to the methyl protons in the compounds. Except for carbamylcholine chloride the double minima have been shown to be due to the two types of methyl groups present in the compounds. The double minima in T₁ for carbamylcholine chloride have been attributed to reorientations of methyl groups bonded to the N atom about the C^′₃ axis and reorientations of each methyl group about its C₃ axis.