Question

Ketoses, like aldoses, give a positive Benedict's test. Explain how this is possible, i.e. how can a ketone become oxidized? Show the reaction mechanism of D-erythrulose as an example.

Answer 1

Solution:

Benedicts test is used to detect the presence of reducing sugars yielding positive result, it includes all monosaccharides and few dischharides like maltose and lactose in the test.

The ketose fructose belongs to the group of alpha-hydroxy ketones hence it gets reduced by Benedicts reagent by converting to aldose flucose and mannose.

The structure of D-Erythrulose is given above, by simplifying its representation as R-CH=O and the reduction by Benedicts test is shown below,