Further Chemistry of l-Ascorbic Acid

Some reactions of L-ascorbic acid have been mentioned in connection with the original structure determination of the molecule. These and others will be expanded upon in the following sections. 

3-di-O-methyl-L-ascorbic acid undergoes both further methyla-tion with iodomethane and silver oxide to give the 2,3,5,6-tetra-O- 

Acid-catalysed esterification of ascorbic acid, e.g. acetylation, produces initially the O-6-acylated derivative and, under more stringent conditions, a 5,6-diester. Fhe crystalline 5,6-diacetate is well known. More vigorous conditions still are needed to obtain the 2,3,4,6-tetra-acetate. 

The rate of aerobic oxidation of ascorbic acid depends on the pH, exhibiting maxima at pH 5 and 11.5. However, the reaction is much more rapid and the degradation more extensive in alkali. Degradative oxidation also occurs, albeit slowly, under anaerobic conditions. 

Irradiation of aqueous ascorbic acid with ultraviolet, X-, and y-radiation has been found to cause free-radical, photochemical oxidation under both aerobic and anaerobic conditions. 

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