Alcohol oxidation


Alcohol oxidation is an important organic reaction. Primary alcohols can be oxidized either
The indirect oxidation of primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate by reaction with water. The oxidation of a primary alcohol at the aldehyde level is possible by performing the reaction in absence of water, so that no aldehyde hydrate can be formed.

Oxidation to aldehydes

Oxidation of alcohols to aldehydes is partial oxidation; aldehydes are further oxidized to carboxylic acids. Conditions required for making aldehydes are heat and distillation. In aldehyde formation, the temperature of the reaction should be kept above the boiling point of the aldehyde and below the boiling point of the alcohol.
Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include:
Allylic and benzylic alcohols can be oxidized in presence of other alcohols using certain selective oxidants such as manganese dioxide.

Oxidation to ketones

Reagents useful for the oxidation of secondary alcohols to ketones, but normally inefficient for oxidation of primary alcohols to aldehydes, include chromium trioxide in a mixture of sulfuric acid and acetone and certain ketones, such as cyclohexanone, in the presence of aluminium isopropoxide. Another method is oxoammonium-catalyzed oxidation. Additionally, sodium hypochlorite in acetone has been reported for efficient conversion of secondary alcohols in the presence of primary alcohols.

Oxidation to carboxylic acids

The direct oxidation of primary alcohols to carboxylic acids can be carried out using
Alcohols possessing two hydroxy groups located on adjacent carbons —that is, 1,2-diols— suffer oxidative breakage at a carbon-carbon bond with some oxidants such as sodium periodate or lead tetraacetate, resulting in generation of two carbonyl groups. The reaction is also known as glycol cleavage.