Ethane-1,2-dial

Suitable dialdehydes can also undergo intramolecular hydride transfer, as in the Cannizzaro reaction of ethan- 1,2-dial (55, glyoxal ) — hydroxyethanoate ( glycollate, 56) anion,... 

Problem 15.19 For the Cannizzaro reaction, indicate (a) why the reaction cannot be used with aldehydes having anaH, —CHCHO U>) the role of OH and OD (Problem 15.18) (c) the reaction product with ethane-dial, O = CH—CH = O (d) the reaction products of a crossed-Cannizzaro reaction between (i) formaldehyde and benzaldehyde, and (ii) benzaldehyde and / - c h I o ro be n zaidehyde. 

More than 300 compounds had been identified in cocoa volatiles, 10% of which were carbonyl compounds (59,60). Acetaldehyde, 2-methylpropanal, 3-methylbutanal, 2-methylbutanal, phenylacetaldhyde and propanal were products of Strecker degradation of alanine, valine, leucine, isoleucine, phenyl-acetaldehyde, and a-aminobutyric acid, respectively. Eckey (61) reported that raw cocoa beans contain about 50-55% fats, which consisted of palmitic (26.2%), stearic (34.4%), oleic (37.3%), and linoleic (2.1%) acids. During roasting cocoa beans these acids were oxidized and the following carbonyl compounds might be produced - oleic 2-propenal, butanal, valeraldehyde, hexanal, heptanal, octanal, nonanal, decanal, and 2-alkenals of Cg to C-q. Linoleic ethanal, propanal, pentanal, hexanal, 2-alkenals of to C q, 2,4-alkadienals of Cg to C-q, methyl ethyl ketone and hexen-1,6-dial. Carbonyl compounds play a major role in the formation of cocoa flavor components. 

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