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Several methods for the oxidation of aldehydes to the corresponding carboxylic acids are known.1,2 However, no one seems to be completely satisfactory, the major drawbacks being high costs, low selectivities, and complex operating conditions. Their application to large-scale preparations is therefore difficult.We thus addressed our attention to the use of the inexpensive sodium chlorite,1 23 which reacts with aldehydes under very mild conditions to give carboxylic acids (eq 1).RCHO + HC102 -RCOOH + HOC1(1)However, hypochlorite ion must be removed in order to avoid side reactions, since the redox pair HOC1/CT is a more powerful oxidant than C102"/H0C1.4 5Another drawback is the oxidation of C102™ to C102 according to eq 2.38,5 HOC1 + 2C1CV -2C102 + Cl" + OH*(2) 2-Methyl-2-butene,78,8 resorcinol,38•7 and sulfamic acid38•9 have been tested as HOC1 scavengers. 2-Methyl-2-butene must be used in a very large excess. Resorcinol is converted into 4-chloro-1,3-dihydroxybenzene, which must be removed from the reaction mixture. Sulfamic acid works well in the oxidation of hydroxylated aromatic aldehydes, but it gave poor results in the case of ,/3-unsaturated aldehydes (see below).

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