AbstractThe bands at 2485 and 940 cm−1observed in the Raman spectra of 2,5‐dimercapto‐1,3,4‐thiadiazole represent the hydrogen‐bonded ν(SH) stretching and δ(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‐bonded and the free δ(C‐SH) 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‐bond formation was obtaine