Remarkable changes in conformations of n-alkanes with their carbon numbers and aromatic solvents

Based on magnetic anisotropy in NMR, it is found that preferred conformations of n-alkanes in aromatic solvents (C6D6 and 1-chloronaphthalene) are dependent both on their carbon numbers and on the solvents used. A short-chain alkane, hexane, tends to adopt extended conformations in both C6D6 and 1-chloronaphthalene. In contrast, a long-chain alkane, dodecane, in 1-chloronaphthalene prefers to take open conformations, though in C6D6 taking U-shaped conformations. A ‘conformational change model’ is proposed on the basis of the NMR results.