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 Ascorbic acid is synthesized from glucose through a five-step process. Firstly, glucose, a pentahydroxy aldose, is reduced to sorbitol, which is then oxidized by the microorganism Acetobacter suboxydans. To selectively oxidize only one of the six hydroxy groups in sorbitol, an enzymatic reaction is involved. Treatment with propanone (acetone) and an acid catalyst then protects four of the remaining hydroxyl groups in acetal linkages. The unprotected hydroxyl group is chemically oxidized to the carboxylic acid by reaction with sodium hypochlorite (bleaching solution). Hydrolysis with acid then removes the two acetal groups. The removal then causes an internal ester-forming reaction to yield ascorbic acid. Each of the five steps has a yield larger than 90% |