3,4-Dichloro-1,2,5-thiadiazole is the heterocycle with the formula . It is a colorless liquid. The compound is produced by treating cyanogen with disulfur dichloride. The compound can also be prepared from aminoacetonitrile.
It is a planar molecule consisting of a thiadiazole core with two chlorine atoms as substituents. The chloride groups are displaced readily by ammonia to give the diamine: