What is the oxidation product of thiols?

1 Answer
Jan 23, 2016

Great question!

While oxygen-based alcohols generally oxidize to form aldehydes and carboxylic acids, thiols can oxidize in TWO different ways--- losing a hydrogen or gaining an oxygen each give surprisingly different paths.

The more common oxidation products are shown below:

The starting reactant is called a thiol.

It can either lose protons to form a disulfide bond (#"R"-"S"-"S"-"R"#) or gain oxygens to form a short-lived sulfenic acid. That eventually forms a sulfinic acid and then a sulfonic acid.

(As an aside, an example of a naturally occurring disulfide bond is when the amino acid cysteine makes disulfide bonds in oxidizing conditions.)

When a thiol loses two hydrogens to form a disulfide bond, it can then further gain oxygens via carbonic acid oxidation (or nitric acid) to form hypervalent sulfones (such as sulfolane), which continue all the way to the sulfonic acid.