Examining thermolysis reactions and tautomerism of 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,5-dimercapto-1,3,4-thiadiazole

A series of high-vacuum thermolysis experiments with 2,5-dimercapto-1,3,4-thiadiazole and 2-mercapto-5-methyl-1,3,4-thiadiazole was performed between ambient temperature and 800 degreesC. The thermolysis products were trapped by matrix-isolation techniques and characterised by IR spectroscopy. Thermolysis of 2,5-dimercapto-1,3,4-thiadiazole gave HNCS, CS2 and HCN, whereas 2-mercapto-5-methyl-1,3,4-thiadiazole shows a more complex fragmentation pattern forming HNCS, CH3NCS, HCN and CS2. Formation of CH3CN was not observed. The molecular structures of different isomers of both mercaptothiadiazoles were studied by ab initio and DFT computations.