Pinnick oxidation
The Pinnick oxidation is an organic reaction by which aldehydes can be oxidized into their corresponding carboxylic acids using sodium chlorite (NaClO2) under mild acidic conditions. It was originally developed by Lindgren and Nilsson. The typical reaction conditions used today were developed by G. A. Kraus. H.W. Pinnick later demonstrated that these conditions could be applied to oxidize α,β-unsaturated aldehydes. There exist many different reactions to oxidize aldehydes, but only a few are amenable to a broad range of functional groups. The Pinnick oxidation has proven to be both tolerant of sensitive functionalities and capable of reacting with sterically hindered groups. This reaction is especially useful for oxidizing α,β-unsaturated aldehydes, and another one of its advantages is its relatively low cost.
The proposed reaction mechanism involves chlorous acid as the active oxidant, which is formed under acidic conditions from chlorite.
First, the chlorous acid adds to the aldehyde. Then resulting structure undergoes a pericyclic fragmentation in which the aldehyde hydrogen is transferred to an oxygen on the chlorine, with the chlorine group released as hypochlorous acid (HOCl).
The HOCl byproduct is itself a reactive chemical that can destroy the NaClO2 reactant or cause other undesired reactions with the organic materials. To prevent this interference, various scavengers are usually added to the reaction to consume the HOCl as it is formed.
The most general problem with the HOCl is that it reacts readily with unreacted chlorite ions, making that material unavailable for the intended Pinnick oxidation reaction:
An additional interference is that HOCl can react with double bonds in the organic reactant or product via a halohydrin formation reaction. However, one can take advantage of the propensity of HOCl to undergo this addition reaction by adding a sacrificial alkene-containing chemical to the reaction mixture. This alternate substrate reacts with the HOCl, preventing the HOCl from undergoing reactions that interfere with the Pinnick reaction itself. 2-Methyl-2-butene is often used in this context:
...
Wikipedia