The simplified reaction is:
C5H11O5-CHO + 2Cu^2+(aq) —> C5H11O5-COOH + Cu2O(s) + H2O
The aldehyde group,-CHO, in the ketohexose (such as glucose, galactose, etc) oxidizes to a carboxyl group, -COOH. That releases electrons which reduce Cu+2 to Cu^+1 (blue cupric citrate to red cuprous oxide).
A more detailed explanation would involve the cyclic structure of glucose and other ketoxexoses, and drawings we can't show here.
Describe the manner in which ketohexose acts as a reducing sugar in the Benedict test.
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