What are thiol groups?

Thiol groups are functional groups in organic chemistry, consisting of a sulfur atom and a hydrogen atom (-SH).

Thiol groups, also known as mercaptan groups, are functional groups found in organic compounds. They are composed of a sulfur atom and a hydrogen atom, represented as -SH. The term 'thiol' comes from the Greek word 'theion' meaning sulfur, combined with 'alcohol', as the group's structure is similar to an alcohol group (-OH) but with a sulfur atom replacing the oxygen atom.

Thiols are characterised by their strong and often unpleasant odours, which are detectable even at very low concentrations. This characteristic makes them useful in a variety of applications, such as in natural gas detection, where an odourant is added to the otherwise odourless gas to alert people to leaks.

In terms of their chemical properties, thiols are known to be more acidic than alcohols. This is due to the larger size and lower electronegativity of sulfur compared to oxygen, which makes the hydrogen atom in the thiol group more easily ionisable. As a result, thiols can lose a proton (H+) to form thiolate anions, which are highly reactive and can participate in a variety of chemical reactions.

Thiols also have the ability to form disulfide bonds, which are crucial in the structure and function of proteins. These bonds are formed when two thiol groups come together, lose two hydrogen atoms as a molecule of hydrogen gas, and form a bond between the two sulfur atoms. This reaction is reversible, and the breaking and reforming of disulfide bonds is a key process in biological systems.

In summary, thiol groups are sulfur-containing functional groups that play important roles in both organic chemistry and biochemistry. Their unique properties, such as their strong odours and ability to form disulfide bonds, make them crucial in a variety of applications and processes.