Aromatic Compounds Containing Nitrogen - Result Question 16
####16. The correct decreasing order for acid strength is
(a) $FCH _2 COOH>NCCH _2 COOH$
(2019 Main, 9 Jan I)
$$
NO _2 CH _2 COOH>ClCH _2 COOH $$
(b) $CNCH _2 COOH>O _2 NCH _2 COOH$
$>FCH _2 COOH>ClCH _2 COOH$
(c) $NO _2 CH _2 COOH>NCCH _2 COOH$
$>FCH _2 COOH>ClCH _2 COOH$
(d) $NO _2 CH _2 COOH>FCH _2 COOH$
$>CNCH _2 COOH>ClCH _2 COOH$
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Answer:
Correct Answer: 16. $(c, d)$
Solution:
- All the given compounds are $\alpha$-monosubstituted acetic acid derivatives and the $\alpha$-substitutions have been made by strong $-I$ groups/atoms. More powerful the $-I$ group, stronger will be the acid.
$-I$ power of different groups is as follows :
$-NO _2>-CN>-F>-Cl$.
Thus, the correct decreasing order for acid strength is:
$NO _2 CH _2 COOH>NCCH _2 COOH>FCH _2 COOH$
$>ClCH _2 COOH$.
