Question:
The correct decreasing order for acid strength is:
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}$