OC-07 CARBOXYLIC ACIDS — 5-MINUTE REVISION CARD
Definition: RCOOH | Most acidic organic functional group | pKa 4–5
Resonance: RCOO– has bond order 1.5 on both C–O | Charge on 2 equivalent O atoms
Acidity Ladder (pKa): RCOOH (4–5) > ArOH (10) > H2O (15.7) > ROH (16–18) > RC≡CH (25)
Acidity Order — Halogens (–I): Cl3CCOOH (0.65) > Cl2CHCOOH (1.26) > ClCH2COOH (2.87) > HCOOH (3.75) > CH3COOH (4.76) > (CH3)3CCOOH (5.05)
Rule: More Cl → stronger acid. Alkyl group → weaker acid. Closer –I → stronger effect.