1H NMR study of hindered internal rotation of tetramethylthiuram disulfide in binary dimethyl sulfoxide-chloroform mixtures

Hindered internal rotation about the C-N single bonds joining the thiuram disulfide was studied by H-1 NMR complete line-shaped analysis in different dimethyl sulfoxide-chloroform (DMSO-CDCl3) mixtures. From the temperature dependence of methyls proton spectra, activation parameters (E-a, DeltaH(not equal), DeltaS(not equal), and DeltaG(not equal)) were obtained. The Arrhenius plots showed a distinct isokinetic temperature at about 35 degreesC at which the exchange rate is more or less independent of the solvent composition. The resulting DeltaH(not equal) against TDeltaS(not equal) plot showed a firmly good linear correlation, indicating the existence of an enthalpy-entropy composition in an exchange process.