Fructose is a ketohexose. The keto group is positioned at which carbon

The correct answer is Option (1) → Carbon 2

Fructose, like glucose, has the formula \( \ce{C6H12O6} \) with six carbon atoms in a straight chain. Glucose is an aldohexose, with the aldehyde group at C1. Fructose is a ketohexose: its carbonyl group is a ketone group, and it sits at carbon number 2, between the \( \ce{CH2OH} \) group (C1) and the rest of the chain:

    \( \displaystyle \ce{CH2OH-CO-(CHOH)3-CH2OH} \)

Counting from the left, C1 is the first \( \ce{CH2OH} \), C2 is the C=O carbon, C3 to C5 are the CHOH carbons and C6 is the last \( \ce{CH2OH} \).

So the keto group of fructose is at carbon 2. In its cyclic (furanose) form, the –OH at C5 adds to this C2 carbonyl group.

NCERT (2026-27 edition):
Structure of Fructose