Spectroscopic and thermodynamic evidence of dimer and trimer hydrogen bonded complex formation between chloroform and...

FT-Raman and FT-infrared spectra of pure chloroform (A) and 2-butanone (B), as well as of the binary system chloroform + 2-butanone, were recorded to investigate the type and nature of the intermolecular complexes formed when both chemicals are mixed. The optimized structures and vibrational frequencies for 2-butanone, chloroform, and their 1:1 and 1:2 complexes were calculated by means of density functional theory (DFT) techniques using the B3LYP functional combined with the 6-31G(d,p) and 6-311++G(d,p) basis set. The recorded FTIR and Raman spectra confirm the existence of these types of hydrogen-bonded complexes, making it possible, furthermore, to calculate the heteroassociation constants. Heat of mixing at 303 K over the whole mole fraction range at atmospheric pressure was also measured. The excess molar enthalpy was fitted to a Redlich-Kister-type equation, using least-squares to obtain its dependence on concentration. The ideal associated solution model was also used to calculate these equilibrium constants among the chemical species in solution, which compare well with that calculated with the spectral determinations and the enthalpy of hydrogen bond formation. Furthermore, the McGlashan-Rastogi linearization test was also used to provide thermodynamic evidence about the stoichiometry of the formed complexes.