Sugar which does not give reddish brown precipitate with Fehling's...

Sucrose does not give Fehling's test positive, and it does not have any aldehyde or ketone group free to undergo oxidation.

It is used to distinguish between aldehyde and ketone. Aldehydes are easily oxidized and give positive Fehling’s test. Ketones apart from alpha-hydroxy-ketones do not give positive Fehling’s test as they are not oxidized easily. Aldose monosaccharides and ketose monosaccharides both give positive Fehling’s test. Presence of glucose in urine can be determined using Fehling’s test.