Carbon dioxide ascorbic acid reduction

On treatment with aqueous mineral acid, L-ascorbic acid,90 hexu-ronic acids,91 and glycuronans92 undergo decarboxylation by which 1 mole of carbon dioxide per mole of acid is produced. For hexu-ronic acids, other detectable products include 2-furaldehyde (27) (Ref. 93), reductic acid (2,3-dihydroxy-2-cyclopenten-l-one, 75 see p. 207) (Refs. 53 and 94-96), and traces of 5-formyl-2-furoic acid... 

Keto and 5-keto aldonic acids also give carbon dioxide and furfural (see below) in yields similar to those for the uronic acids. However, ascorbic acid, as discussed later, gives a very high yield (above 80%) of furfural. Reductic acid, an enolic substance similar in structure to the ascorbic... 

---