A study of van der Waals complexes of 1,2-dichloroethane in paraffin oil by FTIR spectroscopy and ab initio calculations

• Weak interactions of 1,2-dichloroethane in paraffin oil were studied.
• Conformers of 1,2-dichloroethane are involved in the complexation, forming tg-dimer.
• Structure of tg-dimer were determined from the DFT calculations.
• The complexation enthalpy was determined from FTIR spectra.

Weak molecular interactions of 1,2-dichloroethane dissolved in paraffin oil were investigated by FTIR spectroscopy. Occurrence of isosbestic points in the spectra along with the factor analysis showed that DCE⋯DCE dimers are formed in solutions at DCE concentrations between 7 and 15 vol.%. It was found that both trans and gauche conformers are involved in the complexation, forming a tg-dimer. From the spectra collected at 200–222 K, the complexation enthalpy was determined: −4.2 ± 0.4 kcal mol−1. The equilibrium geometry of tg-dimer and the vibrational frequencies were determined from the density functional calculations performed at B3LYP/6-311++G(d,p) and 6-31G(d,p) levels. The C–C bonds of the two molecules involved in tg-dimers were found to be oriented nearly perpendicular to each other. The complexation energy calculated using 6-31G(d,p) and 6-311++G(d,p) basis sets was found to be −1.59 and −1.52 kcal mol−1, respectively.

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