Dimercapto-1,2,4-thiadiazole properties

Due to the electron attraction of the ring, the NH groups in amido-thiadiazoles and thiadiazolylhydrazones (54) have weakly acidic character. Potential mercapto compounds have distinctly acidic properties, and 2,5-dimercapto-l,3,4-thiadiazole and its 4-sub-stituted derivatives are strong acids. The pK and some pKn values of these compounds are found in Table III. 

The properties of mercapto-l,2,4-thiadiazoles, particularly those of the interesting 3,5-dimercapto compound (perthiocyanic add) have been established in fair detail for some time3 recent work has in the main been supplementary in nature. Attention is drawn to the extensive use of 5-mercapto-l,2,4-thiadiazoles in the production of cephalosporin derivatives this is briefly reviewed separately at the end of this Section. 

Bis(dithio)thiadiazoles (e.g., 524)113,515 and bis(thiosulfenamides)516 are employed as corrosion inhibitors in lubricants. The antiwear and extreme-pressure properties of lubricating greases are improved by the addition of (polymeric) 3,5-dimercapto-l,2,4-thiadiazole,517 2,4-dialky 1-1,2,4-thiadiazo-... 

---