The infrared spectra of specifically deuterated n-tridecane-7,7-d₂ pure and mixed with several linear and branched hydrocarbons have been measured as a function of temperature. The average gauche fraction at the middle of the n-tridecane chain has been determined from the intensities of conformation-specific CD₂ rocking bands. The results indicate that the concentration of gauche rotamers in the centre of the n-C₁₃ chains varies with the solvent. For example, when n-tridecane is dissolved in other n-hydrocarbons the gauche concentration decreases when the chain length of the solvent is shorter than n-C₁₃ and increases when the solvent chains are longer than n-C₁₃. However, no simple, direct correlation is found between these solvent-induced changes in gauche concentration and measured thermodynamic quantities of mixing.
Canadian Journal of Chemistry64, no. 8: 1544–1547.