Problem 123 - A Complete Resource Book in Chemistry for JEE Main

Question

The compound 'A' when treated with methyl alcohol and few drops of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) gave smell of winter green. The compound 'A' is (a) oxalic acid (b) tartaric acid (c) salicylic acid (d) succinic acid

Step-by-Step Solution

Answer

The compound 'A' is salicylic acid (c).

Step 1: Understand the Reaction

Compounds that give a smell of wintergreen typically involve an esterification reaction between salicylic acid and an alcohol. The presence of methyl alcohol and sulfuric acid indicates that we are looking at an ester formation.

Step 2: Identify the Reactants

The smell of wintergreen is commonly associated with methyl salicylate. Salicylic acid reacts with methyl alcohol in the presence of sulfuric acid to form methyl salicylate, which has a wintergreen scent.

Step 3: Determine Which Option Matches 'A'

Among the given options, (c) salicylic acid is the only compound that can react with methyl alcohol and sulfuric acid to form methyl salicylate (wintergreen smell). The other acids cannot produce this specific scent.

Key Concepts

Salicylic acid

Salicylic acid is a vital compound often found in skincare products due to its ability to exfoliate and treat acne. But, it’s also significant in chemical reactions. It features an aromatic ring and a carboxyl group, making it effective in esterification reactions. Salicylic acid’s ability to form esters is ideal for laboratory and industrial applications, such as synthesizing methyl salicylate. This particular reaction is catalyzed by acids and involves reacting with alcohol.

• It's utilized in medicinal chemistry for the preparation of other compounds.
• It forms esters readily, like methyl salicylate, known for its pleasant aroma similar to wintergreen.

Understanding this multifaceted compound makes it a crucial part of this esterification process.

Methyl alcohol

Also known as methanol, methyl alcohol is a simple alcohol with a single carbon and the chemical formula \( ext{CH}_3 ext{OH}\). It is a colorless substance that has varied applications, ranging from fuel to serving as an essential solvent in chemical reactions. Methanol reacts effectively with other compounds in esterification reactions, acting as a nucleophile.

• It helps in the production of esters like methyl salicylate.
• Methanol is an excellent solvent, which assists in controlling reaction conditions.

In the context of esterification, methanol's role ensures the successful conversion of salicylic acid into the fragrant compound methyl salicylate.

Sulfuric acid

Sulfuric acid is a highly corrosive and dense acid commonly used in many chemical processes. In chemical synthesis, its role as a catalyst is invaluable. It speeds up reactions without being consumed. During esterification, sulfuric acid is crucial as it donates protons to facilitate the reaction process between carboxylic acids and alcohols.

• Acts by providing protons that increase the electrophilicity of the carboxylic acid.
• Enhances the rate of esterification for efficient production of esters like methyl salicylate.

This highly reactive nature makes sulfuric acid an essential reagent in forming esters that include the pleasant-scented methyl salicylate.