Arrange the following given acids in decreasing order of their Ka values

$F C H_{2} C O O H (P), C l C H_{2} C O O H (Q), O_{2} N C H_{2} C O O H (R), N C C H_{2} C O O H (S)$

Question

Arrange the following given acids in decreasing order of their Ka values F C H 2 C O O H ( P ) , C l C H 2 C O O H ( Q ) , O 2 N C H 2 C O O H ( R ) , N C C H 2 C O O H ( S )

TestHub · Accepted Answer

Acidic character α stability of conjugate base (anion)

As stability of anion $\propto - M$ and $- I$ effect . $- C l$ and $- F$ have $(- I > + M e f f e c t)$ in which $F$ is more electron

withdrawing due to greater electronegativity. $N O_{2}$ and $C N$ have both $- I$ and $- M$ effect with $N O_{2}$ being more electron withdrawing.

Order of $- I -$ effect $- N O_{2} > C N > - F > - C l$ Hence, order of acidity ka will be

$O_{2} N C H_{2} C O O H > N C C H_{2} C O O H > F C H_{2} C O O H > C l C H_{2} C O O H$

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