Seleno-mercaptan

Seleno-mercaptan
A seleno-mercaptan is an organic compound of the formula R-SeH. As such, it is an analogue of alcohols and thiols which contain oxygen and sulfur respectively in place of the selenium atom.

Seleno-mercaptans are toxic, as are the similar mercaptans (thiols), and notably foul-smelling, such that the Guinness Book of Records lists butyl seleno-mercaptan, a natural chemical produced by skunks (C4H9SeH), as a candidate for the foulest-smelling chemical.