Thiol

In organic chemistry, a thiol (; from Ancient Greekθεῖον (theion)'sulfur') or thiol derivative is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SHfunctional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl (−OH) group of an alcohol), and the word is a blend of "thio-" with "alcohol".

Many thiols have strong odors resembling that of garlic, cabbage or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless). The smell of natural gas is due to the addition of thiol.