Question

Which of the following acid has highest $pKa$ value?

• A. $O _{2} NCH _{2} COOH$
• B. $NCCH _{2} COOH$
• C. $FCH _{2} COOH$
• D. $C _{6} H _{5} CH _{2} COOH$

Answer 1

Answer: (D)

Acidic strength $\alpha \frac{1}{ p Ka } \alpha$ stability of conjugate base. $C _{5} H _{5} CH _{3} COOH$ is weakest acid among all so has highest $pKa$ value.