JEE Main · 2024 · 01 Feb 2024 · Shift 2 · General Organic Chemistry

$-N{H}_2$, $-OH$, and $-OR$ each carry a lone pair on the heteroatom that conjugates into an attached $\pi$-system, donating electron density — a positive resonance ($+M$) effect. $-COOH$ instead has its carbon conjugated to the electronegative carbonyl oxygen; the polarised C=O pulls electron density out of the attached system through the $\pi$-framework, so $-COOH$ shows a negative resonance ($-M$) effect.