Read the passage carefully and answer the Questions.

Carboxylic acids are the earliest organic compounds isolated from nature. These are also known as organic acids but are weaker acids as compared to mineral acids. However, they are more acidic than alcohols and phenols because of greater resonance stabilization of the parent acid and its conjugate base. The acidic strength is determined by the Ka, which is called the acidity constant. The greater the value of Ka, the greater the tendency of the acid to ionize and hence the stronger the acid. The acidic strength of the saturated aliphatic carboxylic acid depends upon the inductive effect and its position with respect to - COOH groups. Electron-donating substituents tend to decrease whereas electron -withdrawing substituents tend to increase the acidic strength. The acidic strength of the aromatic carboxylic acid, on the other hand depends upon both the inductive effect and the resonance effect of the substituents.

Which of the following groups when attached directly does not increase the acidity of the carboxylic acid?

Methyl

The correct answer is Option (3) → Methyl **

• Electron-withdrawing groups increase the acidity of carboxylic acids by stabilizing the conjugate base:
• Nitro (–NO₂) → strong electron-withdrawing → increases acidity
• Vinyl (–CH=CH₂) and Phenyl (–C₆H₅) → through resonance/inductive effect can slightly stabilize the conjugate base → may increase acidity
• Methyl (–CH₃) → electron-donating → decreases acidity or does not increase it.

Hence, methyl group does not increase acidity.