organic compounds; ditertiary glycols with —OH groups on adjacent carbon atoms (R represents like or unlike organic radicals).
The simplest of the pinacols is (CH3)2 CC(OH)C(OH)(CH3)2, which is usually called pinacol. The compound forms colorless crystals with a camphor smell, a melting point of 42°C, and a boiling point of 171°-172°C. It is soluble in alcohol and chloroform, poorly soluble in cold water, and readily soluble in hot water. Upon cooling of the aqueous solution, pinacol precipitates in the form of the hexahydrate, called pinacol hydrate (melting point, 46°C), which forms large square tabular crystals (hence the name of pinacols, from Greek pinax, “tablet”).
Pinacols are obtained by bimolecular reduction of ketones under the action of alkali metals, or amalgamated magnesium or aluminium. They are also obtained electrochemically or by irradiation of mixtures of a ketone with isopropyl alcohol. Pinacol is obtained from acetone.
Pinacols participate in most reactions characteristic of tertiary alcohols. Many reactions of pinacols are accompanied by alteration of the carbon skeleton or pinacolic rearrangement.