|Benzopurpurine 4B||Benzoquinonium Chloride||Benzoresorcinol||Benzothiazole||Benzotrichloride|
A pinacol coupling reaction is an organic reaction in which a carbon–carbon covalent bond is formed between the carbonyl groups of an aldehyde or a ketone in presence of an electron donor in a free radical process. The reaction product is a vicinal diol. The reaction is named after pinacol (also known as 2,3-dimethyl-2,3-butanediol or tetramethylethylene glycol), which is the product of this reaction with acetone. The reaction is usually a homocoupling but intramolecular cross-coupling reactions are also possible. Pinacol was discovered by Wilhelm Rudolph Fittig in 1859.