Question

Arrange the protons in the order of increasing acidic strengths :

• A. $X>Z>Y$
• B. $Z<X>Y$
• C. $X>Y>Z$
• D. $Z>X>Y$

Answer 1

The correct option is A $X>Z>Y$

The proton on carboxylic acid is a stronger acid than those on $\stackrel{\oplus }{N{H}_3}$ in amino acid and $\stackrel{\oplus }{-N{H}_3}\left(Y\right)$.
$\left(Z\right)$ is more acidic than (Y) due to $-I$ effect of $(-COOH)$ group which is nearer to $\left(Z\right)$ than $\left(Y\right)$. Hence, the acidic order: $X>Z>Y$.