FOURIER-TRANSFORM RAMAN-SPECTROSCOPIC STUDY OF HYDROGEN-BONDING IN 2,5-DIMERCAPTO-1,3,4-THIADIAZOLE USING AN ENVIRONMENTAL CHAMBER

The bands at 2485 and 940 cm(-1) observed in the Raman spectra of 2,5-dimercapto-1,3,4-thiadiazole represent the hydrogen-bonded nu(SH) stretching and delta(C-SH) in-plane bending modes, respectively. A quantitative study of the hydrogen bonding was carried out using intensity measurements of the bands assigned to the hydrogen-honded and the free delta(CSH) in-plane deformations at 940 and 919 cm(-1), respectively, as a function of temperature. The Fourier transform (FT) Raman spectra were recorded over the temperature range 303-403 K using an environmental chamber fitted into the FT Raman sample compartment. The equilibrium constants between the free and the hydrogen-bonded molecules were determined over this temperature range and the average enthalpy for hydrogen-bead formation was obtained (Delta H degrees = -3.35 +/- 0.2 kJ mol(-1)).