Question

The increasing order of acid strength of the following carboxylic acids is: 
\[ (i) \text{(CH}_3\text{)}_3\text{C-COOH} \quad (ii) \text{(CH}_3\text{)}_2\text{CH-COOH} \quad (iii) \text{CH}_3\text{CH}_2\text{COOH} \]

• A. \( (i)<(ii)<(iii) \)
• B. \( (i)<(iii)<(ii) \)
• C. \( (ii)<(i)<(iii) \)
• D. \( (ii)<(iii)<(i) \)
• E. \( (iii)<(ii)<(i) \)

Hint:

Electron-donating groups reduce acidity by destabilizing the carboxylate ion, while electron-withdrawing groups increase acidity by stabilizing it.

Answer 1

Answer: (E)

The acidity of carboxylic acids is influenced by the electron-donating or withdrawing nature of substituent groups. 
Electron-donating groups decrease acidity, while electron-withdrawing groups enhance acidity. 
- Tertiary butanoic acid \((i)\) has three alkyl groups, making it the strongest acid. 
- Isobutyric acid \((ii)\) has two alkyl groups, making it less acidic than (i). 
- Propionic acid \((iii)\) has only one alkyl group, making it the least acidic. 
Thus, the correct order of increasing acid strength is: \[ {(iii) < (ii) < (i)} \]