1.8.1 Silver (Ag)

Silver in its metalic state is a grey shining soft metal and has a atomic number of 47. The stable oxidation state is +1.

1.8.1.1 Oxidation of Alcohols

Silver based catalysts are considerably investigated for the oxidation of alcohols to carbonyl compounds. For example, silver carbonate (Ag₂CO₃) has been used for the oxidation of primary and secondary alcohols to give aldehydes  and ketones, respectivley (Scheme 1).

Scheme 1

Ag₂CO₃ supported on celite is known as Fetizon’s reagent. This reagent oxidizes alcohols selectively under mild reaction conditions (Scheme 2). The reaction is performed under apolar solvents such as benzene, heptane but the polar solvents hinder the oxidation.

Scheme 2

 

1.8.1.2 Oxidation of Phenols

Phenols could be oxidized to a variety of products depending on the nature of substituent present in the aromatic ring. For example, 2,6-disubstituted phenols when treated with Ag₂CO₃ undergoes dimerization to provide diphenoquinones, while substituted 1,4-catecols are oxidized to give substituted benzoquinones (Scheme 3).

Scheme 3

 

1.8.1.3 Oxidation of Aldehydes to Carboxylic Acids

Silver oxide (AgO) has been found to catalyze the oxidation of aldehydes to give carboxylic acids in good yield (Scheme 4).

Scheme 4