In chemistry, thiols (formerly known as mercaptans) are those compounds which contain the sulfhydryl group -SH attached to a carbon atom.

Thiols are similar to alcohols, with the oxygen of the hydroxyl group -OH being replaced by a sulfur atom. (Oxygen and sulfur have similar chemical properties, as they belong to the same periodic table group.) Thiols form thioethers, thioacetals and thioesters, in which the alcohol-derived oxygen atom is replaced by a sulfur atom.

Many thiols are colorless liquids having an odor resembling that of garlic. The odor is strong and repulsive. Thiols bind strongly to skin proteins, and are responsible for the intolerable, persistent odor produced by the spraying of skunks.

Natural gas distributors began adding various forms of thiols to natural gas, which is naturally odorless, after the deadly 1937 New London School explosion.

When a thiol group is a substituent in an alkane, there are several ways of naming the resulting thiol:

• The preferred method (used by the IUPAC) is to add the suffix -thiol to the name of the alkane. Example: CH₃SH would be methanethiol.
• An older method, the word mercaptan replaces alcohol in the name of the equivalent alcohol compound. Example: CH₃SH would be methyl mercaptan.

Examples of thiols:

• Methanethiol - CH₃SH
• Ethanethiol - C₂H₅SH
• Coenzyme A
• Lipoamide
• Glutathione
• Cysteine.

Etymology

Looking at thiol binding states for metals, particularly mercury, one can see the reason for the name mercaptan, from the Latin mercurius captans, laying hold of mercury.

External links

• Mercaptan, by The Columbia Electronic Encyclopedia
• What is Mercaptan?, by Columbia Gas of Pennsylvania and Maryland