Elucidation of the structure of alkane chains in solution by means of 1H NMR

Solvent shifts of a series of alkanes have been studied in perfluorohexane, carbon tetrachloride and diiodomethane. The methylene proton resonances for longer alkyl chains are shifted downfield in perfluorohexane, but upfield in diiodomethane. It is suggested that n-alkanes have a tendency to adopt folded structures in solution, the degree of folding for n-alkane chains in perfluorohexane being larger than that in diiodomethane.