Question

Sort out the following in the order of increasing acidity:

• A. ${\mathrm{NO}}_2{\mathrm{CH}}_2\mathrm{COOH}$
• B. $\mathrm{NC}-{\mathrm{CH}}_2\mathrm{COOH}$
• C. ${\mathrm{CH}}_3\mathrm{COOH}$
• D. ${\mathrm{ClCH}}_2{\mathrm{CH}}_2\mathrm{COOH}$

Answer 1

Electron withdrawing groups increase the acidity of carboxylic acids by stabilising the conjugate base through delocalisation of negative charge by inductive and/or resonance effects. Conversly, electron donating groups decrease the acidity by destabilising the conjugate base.
Acidity$\propto$$\frac{1}{pKa}$
The order of increasing acidity is:
$N{O}_{2}COOH>NC-C{H}_{2}COOH>ClC{H}_{2}C{H}_{2}COOH>C{H}_{3}COOH$