JEE Main 2025 Apr 3 Shift 1, Chemistry Q6: Carbohydrates

L-fructose is the mirror image of D-fructose. D-fructose has the Fischer projection (top to bottom): ${\text{CH}}_2\text{OH}$, $\text{C}=\text{O}$, HO on left (C3), H–OH on right (C4), H–OH on right (C5), ${\text{CH}}_2\text{OH}$.

To obtain L-fructose, every horizontal substituent is reflected: the C3 hydroxyl moves to the right, while the C4 and C5 hydroxyls move to the left. The reference C5 carbon must carry its OH on the left, which is the defining feature of the L-series.

Option (3) shows this Fischer projection and is therefore the correct structure of L-fructose.