Nitrile to Carboxylic Acid Transformation

Note that though this reaction is acid catalyzed where the concentration of add exceeds that of the nitrile, the acid will react with the liberated ammonia by-product in a secondary acid-base 

This is a two-step sequence than can be used when R is an acid-sensitive group. The price of carrying out this methodology is the overall low minimum atom economy (AE) compared with the acid catalyzed option, which is a more direct synthesis. Note that in the second step, the water molecule added after the formation of the diazonium salt is not cancelled with the two water molecules formed prior since part of this water molecule ends up in the final product structure. In the first step, the water and sodium hydroxide molecules cancel each other out in the overall balanced chemical equation. 

Since the entire transformation is hyperhypsic, a net reduction has occurred. This corresponds to one of the oxygen atoms in hydrogen peroxide that is being reduced. The sulfur atom in sodium bisulfite is oxidized to sodium bisulfate, but since the sodium bisulfite reagent is a sacrificial one the oxidation number change at sulfur does not count in the calculation of the hypsicity index. 

---

Not surprisingly, the hydrolysis of nitriles is the most atom economical reaction. The isohypsic transformations are the acid chloride-Schotten-Baumann sequence, carbodiimide and carbonyl-diimidazole methods, and the hydrolysis of nitriles. The oxidation of nitriles with hydrogen peroxide is hyperhypsic for the reasons mentioned in Section 9.1.1 for the nitrile to carboxylic acid transformation. The umpolung method, which electronically reverses the roles of the reacting partners, is hypohypsic since a net oxidation has occurred at the reactive carbon atom. This is a novel... 

---