JEE Main 2026 — Aldehydes and Ketones Question with Solution

Given the molar ratio of C, O, and H in compound $x$ is equal, the empirical formula is $CHO$.

Empirical mass $=12+1+16=29$ g mol${}^{-1}$.

Since the molar mass of $x$ is $58$ g mol${}^{-1}$, the molecular formula is $(CHO{)}_2$ or $C_2{H}_2{O}_2$.

The structure of $x$ is glyoxal, $OHC-CHO$.

Treatment of glyoxal with $50\%$ KOH under reflux results in an intramolecular Cannizzaro reaction. One aldehyde group is oxidized to a carboxylate ion, and the other is reduced to a primary alcohol.

$OHC-CHO\stackrel{50\%\text{ KOH}}{\to }HOC{H}_2-CO{O}^{-}{K}^{+}$

Subsequent acidification yields glycolic acid ($y$).

$HOC{H}_2-CO{O}^{-}{K}^{+}\stackrel{H^{+}}{\to }HOC{H}_2-COOH$

The structure of $y$ is $HO-C{H}_2-COOH$.

Answer: $O=C-OH,C{H}_2-OH$ (with C-C bond)