What will be the decreasing order of basic strength of the following conjugate bases? -OH, R O, CH3CO O, C l
- C l > R O > -OH > CH3CO O
- -OH > R O > CH3CO O > C l
- C l > -OH > R O > CH3CO O
- R O > -OH > CH3CO O > C l
Answer
(4) R O > -OH > CH3CO O > C l
Solution
Stronger the acid ⇒ weaker its conjugate base.
Acid strength: HCl > CH3COOH > H2O > ROH
(pKa ≈ −7, 4.76, 15.7, 16–18)
∴ Base strength: R O > -OH > CH3CO O > C l
∵ R (+I) pushes electron density onto O in RO-; CH3COO- is resonance-stabilised; Cl- is the conjugate base of a strong acid.
Answer: (4)