# The correct decreasing order for acid strength is:

Question:

The correct decreasing order for acid strength is:

1. $\mathrm{NO}_{2} \mathrm{CH}_{2} \mathrm{COOH}>\mathrm{FCH}_{2} \mathrm{COOH}>$$\mathrm{CNCH}_{2} \mathrm{COOH}>\mathrm{ClCH}_{2} \mathrm{COOH} 2. \mathrm{FCH}_{2} \mathrm{COOH}>\mathrm{NCCH}_{2} \mathrm{COOH}>$$\mathrm{NO}_{2} \mathrm{CH}_{2} \mathrm{COOH}>\mathrm{ClCH}_{2} \mathrm{COOH}$

3. $\mathrm{CNCH}_{2} \mathrm{COOH}>\mathrm{O}_{2} \mathrm{NCH}_{2} \mathrm{COOH}>$$\mathrm{FCH}_{2} \mathrm{COOH}>\mathrm{ClCH}_{2} \mathrm{COOH} 4. \mathrm{NO}_{2} \mathrm{CH}_{2} \mathrm{COOH}>\mathrm{NCCH}_{2} \mathrm{COOH}>$$\mathrm{FCH}_{2} \mathrm{COOH}>\mathrm{ClCH}_{2} \mathrm{COOH}$

Correct Option: , 4

Solution:

The acidic strength of a compound or an acid depends on the inductive effect (-I). Higher the (-I) effect of a substituent higher will be acidic strength. Now, the decreasing order of $(-\mathrm{I})$ effect of the given substituents is $\mathrm{NO}_{2}>\mathrm{CN}>\mathrm{F}>\mathrm{Cl}$.

$\therefore$ The correct decreasing order of acidic strength amongst the given carboxylic acids is:

$\mathrm{O}_{2} \mathrm{NCH}_{2} \mathrm{COOH}>\mathrm{NCCH}_{2} \mathrm{COOH}>\mathrm{FCH}_{2} \mathrm{COOH}>$$\mathrm{ClCH}_{2} \mathrm{COOH}$

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