Positional dependence of solvent effects on the conformation of liquid n-alkanes. An infrared spectroscopic study

Infrared spectra of specifically deuterated n-tridecane-2,2-d ₂ mixed with several linear and branched hydrocarbons have been recorded. The concentration of gauche bonds at the ends of the tridecane chain was determined from the intensity of the conformation-sensitive CD ₂ rocking vibrations. The results obtained for the gauche concentration at the chains' ends are compared with those previously obtained for the gauche concentration at the centre of the n-tridecane chain (H.L. Casal, P.W. Yang and H.H. Mantsch, Can. J. Chem. 64 (1986) 1544). The concentration of gauche bonds is clearly dependent on the chain position and so are the solvent-induced changes of this concentration.