JEE Main 2025 Jan 22 Shift 1, Chemistry Q15: Properties and Important Reactions of Aldehydes & Ketones

Fehling's reagent (alkaline Cu${}^{2+}$ tartrate complex) gives a positive test (red Cu${}_2$O ppt) with aliphatic aldehydes and $\alpha$-hydroxy ketones (reducing sugars such as fructose).

(A) Furfural (an aromatic aldehyde directly attached to a heteroaromatic ring) does not give a positive Fehling's test, in line with the standard rule that aromatic aldehydes (such as benzaldehyde) fail.

(B) 2-Acetylfuran is a methyl ketone (not an $\alpha$-hydroxy ketone) and therefore does not react.

(C) The structure ${\text{HOCH}}_2-\text{CO}-(\text{CHOH}{)}_3-{\text{CH}}_2\text{OH}$ is fructose, which has an $\alpha$-hydroxy ketone and behaves as a reducing sugar. $✓$

(D) Acetaldehyde, a typical aliphatic aldehyde. $✓$

(E) An aliphatic aldehyde (the $-$CHO is on an sp${}^3$ carbon, not directly on the ring), which gives a positive test. $✓$

$\therefore$ (C), (D), and (E) only.