The correct order of decreasing acidity of the following aliphatic acids is
- HCOOH > CH3COOH > (CH3)2CHCOOH > (CH3)3CCOOH
- HCOOH > (CH3)3CCOOH > (CH3)2CHCOOH > CH3COOH
- (CH3)3CCOOH > (CH3)2CHCOOH > CH3COOH > HCOOH
- CH3COOH > (CH3)2CHCOOH > (CH3)3CCOOH > HCOOH
Answer
(1) HCOOH > CH3COOH > (CH3)2CHCOOH > (CH3)3CCOOH
Solution
Alkyl groups are electron-releasing (+I); they destabilise the carboxylate anion and decrease acidity.
HCOOH has no alkyl group, and the +I effect increases with the number of methyl groups: CH3 < (CH3)2CH < (CH3)3C.
Acidity: HCOOH > CH3COOH > (CH3)2CHCOOH > (CH3)3CCOOH
Answer: (1)