Pinacols

Pinacols

 

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.

References in periodicals archive ?
1] for 4-chlorobenzaldehyde indicates that products are pinacols.
Therefore aim of the work was to investigate and develop a new synthetic method for the preparation and evaluation of Pinacol on easily available conditions (reagent, apparatus, temperature and pH).
The present work deals with the electrochemical reduction of various carbonyl compounds such as (1) Acetone (2) Acetophenone (3) 4-Choloro benzaldehyde was carried out by using the weak acid (Phenol) in aprotic solvent for the synthesis of the Pinacol.
Pinacol is prepared in neutral conditions and chromium (III) salts are added to the solution.
Constant Potential electrolysis as a new eco-friendly synthetic method has been developed for the preparation of Pinacol based on easily available conditions.
The percentage yield of Pinacol synthesized by acetone, Acetophenone and 4-chlorobenzaldehyde were 75%, 85%, 90% respectively.
Acetophenone yields more Pinacol indicating that aromatic ketones are more prone to the formation of the Pinacol.
The principal which governs whether a pinacol or alcohol is formed when the carbonyl compounds is electrolyzed may be classified on the basis of conjugation [11].