Question

Find correct order of acidic strength in the following reaction products \(P, Q, R \& S\):

• A. \(P>Q>R>S\)
• B. \(Q>P>S>R\)
• C. \(Q>S>P>R\)
• D. \(R>S>P>Q\)

Hint:

Among carboxylic acids, {formic acid is stronger than benzoic acid}, and alcohols are much weaker acids than carboxylic acids.

Answer 1

The Correct Option is B

Concept:
Acidic strength depends on the stability of the conjugate base.

Electron-withdrawing groups increase acidity.
Carboxylic acids are more acidic than alcohols and hydrocarbons.
Aromatic acids with strong \(-I\) or \(-M\) effects are stronger.

Step 1: Identify the Products
(I) Product \(P\):
Aniline undergoes diazotization followed by Sandmeyer reaction to give benzonitrile, which on acidic hydrolysis forms benzoic acid
. \(\Rightarrow\) Aromatic carboxylic acid (strong acid among given). (II) Product \(Q\):
Methane undergoes controlled oxidation to give formic acid
. \(\Rightarrow\) Strongest acid among the products. (III) Product \(R\):
Propane oxidized by manganese acetate gives secondary alcohol/ketone type product
. \(\Rightarrow\) Weakly acidic. (IV) Product \(S\):
Toluene undergoes NBS bromination followed by hydrolysis to give benzyl alcohol/benzoic derivative
. \(\Rightarrow\) Less acidic than carboxylic acids but more than hydrocarbons.
Step 2: Compare Acidic Strength
\[ \text{Formic acid }(Q)>\text{Benzoic acid }(P)>S>R \] \[ \boxed{Q>P>S>R} \]