How Are Aldehydes and Ketones Oxidized

In practice, this type of nucleophilic substitution is generally carried out in the presence of a weak base such as potassium carbonate to neutralize the HX as it is formed. 

Aldehydes are oxidized to carboxylic acids by a variety of common oxidizing agents, including chromic acid and molecular oxygen. In fact, aldehydes are one of the most easily oxidized of all functional groups. Oxidation by chromic acid (Section 8.2F) is illustrated by the conversion of hexanal to hexanoic acid  

Aldehydes are also oxidized to carboxylic acids by silver ion. One common laboratory procedure uses Tollens reagent, prepared by dissolving AgN03 in water, adding sodium hydroxide to precipitate silver ion as AggO, and then adding aqueous ammonia to redissolve silver ion as the silver-ammonia complex ion  

When Tollens reagent is added to an aldehyde, the aldehyde is oxidized to a carboxylic anion, and Ag is reduced to metallic silver. If this reaction is carried out properly, silver precipitates as a smooth, mirrorlike deposit—Whence the name silver-mirror test  

Nowadays, Ag is rarely used for the oxidation of aldehydes, because of the cost of silver and because other, more convenient methods exist for this oxidation. The reaction, however, is still used for silvering mirrors. In the process, formaldehyde or glucose is used as the aldehyde to reduce Ag.  

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