Question

Which of the following will give a pleasant smell of ester when heated with ethanol and a small quantity of sulphuric acid?

• A. Acetic acid
• B. Ethanol
• C. Methanol
• D. Ethanal

Hint:

Esterification requires:
\[ \text{Carboxylic Acid} + \text{Alcohol} \xrightarrow{\text{Acid Catalyst}} \text{Ester} + \text{Water} \]
Identify the carboxylic acid from the options to find the answer immediately.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks which chemical substance reacts with ethanol in the presence of an acid catalyst to produce a pleasant-smelling ester.

Step 2: Key Formula or Approach:
The reaction of a carboxylic acid with an alcohol in the presence of concentrated sulfuric acid as a catalyst to form an ester is known as the esterification reaction:
\[ \text{R-COOH} + \text{R'-OH} \xrightarrow{\text{H}_2\text{SO}_4} \text{R-COOR'} + \text{H}_2\text{O} \]

Step 3: Detailed Explanation:

• The problem states that the reagent is heated with ethanol (\(\text{C}_2\text{H}_5\text{OH}\)), which is an alcohol, and concentrated sulphuric acid (\(\text{H}_2\text{SO}_4\)), which acts as a dehydrating agent and catalyst.

• To undergo esterification, an alcohol must react with a carboxylic acid.
- Out of the choices, Acetic acid (\(\text{CH}_3\text{COOH}\)) is a carboxylic acid.

• When acetic acid is heated with ethanol in the presence of concentrated sulfuric acid, they undergo a condensation reaction to form the ester ethyl acetate, which has a distinct, sweet, and fruity smell:
\[ \text{CH}_3\text{COOH(l)} + \text{C}_2\text{H}_5\text{OH(l)} \xrightarrow{\text{H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5\text{(l)} + \text{H}_2\text{O(l)} \] - This pleasant, fruity-smelling compound is ethyl acetate (an ester).


Step 4: Final Answer:
The reactant is acetic acid.