Question

Which of the following as the lowest $p{K}_a$ value?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

The acidic nature of compound depends on the stability of its conjugate base.
The order of acidic nature of given compounds is d>c>b>a.
Greater the acidity of an acid, lower is its $p{K}_a$ value and higher value of $K_a$.
So, the order of $p{K}_a$ value of given compounds a>b>c>d.
So, the lowest $p{K}_a$ value is of Propiolic acid. Hence, Option ''d'' is the correct answer.