HYDROGEN-BONDING IN CHCL3 DMSO-D(6) AND CDCL3/DMSO-H(6) MIXTURES/

Raman and IR spectra of solutions of CHCl3/DMSO-d(6) and CDCl3/DMSO-h( 6) (DMSO dimethyl sulfoxide) solutions are presented and analyzed in t erms of hydrogen-bonding interactions. In the region of the C-H stretc h of CHCl3 or the C-D stretch of CDCl3, addition of DMSO causes 3 new band to appear which is broadened and red-shifted with respect to the free C-H or C-D stretch. We postulate that this new band derives from chloroform hydrogen-bonded to DMSO and compare the relative intensitie s of the bands due to complexed and free chloroform to the ratio of th e concentrations of the two species, calculated according to published equilibrium constants. It is concluded that complexation leads to con siderable enhancement of the inherent Raman and infrared intensities o f the C-H and C-D stretch. The vibrational spectra reveal evidence tha t both 1:1 and 2:1 (2 chloroform to 1 DMSO) complexes form and that th e intensity enhancement of the C-H or C-D stretch is larger for the fi rst than the second hydrogen bond. The general features of the hydroge n-bonded C-H and C-D stretch are compared to those of other hydrogen-b onded systems, and possible explanations for the intensity enhancement are considered.