N-oxides and related compounds. Part XXVII. A proton magnetic resonance investigation of the interaction of pyridines with some Lewis acids

Abstract

The variation is discussed of the chemical shifts of ring protons of a series of methyl-substituted pyridines in the following solvents: arsenic trichloride, phosphorus trichloride, sulphur dioxide, carbon tetrachloride, and cyclohexane. The solvent shifts for the first three solvents are shown to be qualitatively similar although quantitatively less than for trifluoroacetic acid. No evidence was found for back-co-ordination in pyridine complexes with arsenic trichloride or phosphorus trichloride.