Thiol

"The most striking characteristic of thiols is their appalling odor. Skunk scent, for instance, is caused primarily by the simple thiols 3-methyl-1-butanethiol and 2-butene-1-thiol. Volatile thiols such as ethanethiol are also added to natural gas and liquefied propane to serve as an easily detectable warning in case of leaks."

"Thiols can be oxidized by Br2 or I2 to yield disulfides (RSSR′). The reaction is easily reversed, and a disulfide can be reduced back to a thiol by treatment with zinc and acid."