JEE Main 2026 Apr 6 Shift 2, Chemistry Q13: Carboxylic Acid Derivatives

Esters are stabilised by resonance: the lone pair on the single-bonded oxygen delocalises into the C=O system. The dominant resonance structure has the formal C=O double bond ($\alpha$); a contributing structure shifts that double bond to the C–O–CH${}_3$ side ($\beta$).

Effect on bond orders: $\alpha$ has partial single-bond character (slightly longer than a pure C=O); $\beta$ has partial double-bond character (shorter than a pure C–O single bond); $\gamma$ is a plain C(sp${}^3$)–O single bond to the methyl, longest.

Order: $\alpha <\beta <\gamma$.