JEE Advanced levelSingle correct optionDifficulty 3 of 3bm180
Assertion (A): D-fructose gives a positive Fehling's test although it is a ketose.
Reason (R): In alkaline medium fructose rearranges through an enediol to aldose forms (glucose and mannose) that are oxidised.
ABoth A and R are true, but R is not the correct explanation of A
BBoth A and R are true, and R is the correct explanation of A
CA is true but R is false
DA is false but R is true
Answer: B
Under the basic conditions of Fehling's reagent, the ketose tautomerises via the 1,2-enediol to aldohexoses, which reduce Cu(II). So A is true and R is its correct explanation.