Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.

Q: Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.

**Esterification Reaction:** The reaction between a carboxylic acid and an alcohol in the presence of an acid catalyst to produce a sweet-smelling compound called an ester is known as an esterification reaction. For example, when ethanoic acid reacts with ethanol in the presence of an acid catalyst (such as concentrated sulphuric acid), ethyl ethanoate (an ester) and water are formed. $$\text{Chemical Equation: } \underset{ ext{Ethanoic acid}}{CH_3COOH} + \underset{ ext{Ethanol}}{CH_3CH_2OH} \xrightarrow{ ext{Acid Catalyst}} \underset{ ext{Ethyl ethanoate (Ester)}}{CH_3COOCH_2CH_3} + H_2O$$ --- **Activity to Demonstrate Esterification:** 1. **Apparatus/Reagents Required:** Ethanol ($1\text{ mL}$), glacial acetic acid ($1\text{ mL}$), a few drops of concentrated sulphuric acid, test tube, beaker, water, tripod stand, wire gauze, burner, and water bath. 2. **Procedure:** - Take $1\text{ mL}$ of ethanol (absolute alcohol) and $1\text{ mL}$ of glacial acetic acid in a test tube. - Add a few drops of concentrated sulphuric acid to the mixture. - Warm the test tube in a water bath containing hot water for at least $5\text{ minutes}$ (Do not heat the test tube directly over a flame as alcohol is highly inflammable). - Pour the contents of the test tube into a beaker containing $20-50\text{ mL}$ of water. 3. **Observation:** A sweet, fruity smell is detected emanating from the beaker. 4. **Conclusion:** The sweet, fruity smell confirms the formation of an ester (ethyl ethanoate) via the esterification reaction. ```diagram {"xrange": [82.0, 268.0], "yrange": [-285.2, -24.8], "polygons": [{"points": [[150.0, -100.0], [250.0, -100.0], [250.0, -220.0], [150.0, -220.0]]}], "lines": [{"from": [200.0, -50.0], "to": [200.0, -180.0], "label": "Test Tube with Reaction Mixture"}], "points": [{"x": 200.0, "y": -160.0, "label": "Water Bath (Beaker)"}, {"x": 100.0, "y": -260.0, "label": ""}]} ```

Carbon and its Compounds

Chemical Properties of Carbon Compounds

Official Answer

Esterification Reaction:

The reaction between a carboxylic acid and an alcohol in the presence of an acid catalyst to produce a sweet-smelling compound called an ester is known as an esterification reaction.

For example, when ethanoic acid reacts with ethanol in the presence of an acid catalyst (such as concentrated sulphuric acid), ethyl ethanoate (an ester) and water are formed.

$\text{Chemical Equation: } \underset{ ext{Ethanoic acid}}{CH_3COOH} + \underset{ ext{Ethanol}}{CH_3CH_2OH} \xrightarrow{ ext{Acid Catalyst}} \underset{ ext{Ethyl ethanoate (Ester)}}{CH_3COOCH_2CH_3} + H_2O$

Activity to Demonstrate Esterification:

Apparatus/Reagents Required: Ethanol ( $1\text{ mL}$ ), glacial acetic acid ( $1\text{ mL}$ ), a few drops of concentrated sulphuric acid, test tube, beaker, water, tripod stand, wire gauze, burner, and water bath.
Procedure:

Take $1\text{ mL}$ of ethanol (absolute alcohol) and $1\text{ mL}$ of glacial acetic acid in a test tube.
Add a few drops of concentrated sulphuric acid to the mixture.
Warm the test tube in a water bath containing hot water for at least $5\text{ minutes}$ (Do not heat the test tube directly over a flame as alcohol is highly inflammable).
Pour the contents of the test tube into a beaker containing $20-50\text{ mL}$ of water.

Observation: A sweet, fruity smell is detected emanating from the beaker.
Conclusion: The sweet, fruity smell confirms the formation of an ester (ethyl ethanoate) via the esterification reaction.

EsterificationCarboxylic acidAlcoholAcid catalystEthyl ethanoateFruity smellWater bath

Marking Scheme

10.5 marks
21 mark
31 mark
40.5 marks

Hint

Think of the reaction between ethanoic acid and ethanol. Remember that esters are characterized by their sweet, fruity smell, and a water bath is essential for safety.

Quick Oral Answer

Esters are sweet-smelling substances. When treated with an alkali like sodium hydroxide, they are converted back into alcohol and the sodium salt of carboxylic acid. This reverse reaction is called saponification because it is used in the preparation of soap.

Analysis & Explanation

Esterification is a reversible condensation reaction. The acid catalyst (usually concentrated $H_2SO_4$ ) protonates the carbonyl oxygen of the carboxylic acid, making the carbonyl carbon more electrophilic and susceptible to nucleophilic attack by the oxygen atom of the alcohol. Concentrated $H_2SO_4$ also acts as a dehydrating agent, shifting the equilibrium forward by removing the water formed during the reaction. Direct heating of the test tube is strictly avoided because ethanol is highly volatile and flammable; hence, a water bath is used.

Common Mistakes

1Heating the reaction mixture directly over an open flame instead of using a water bath.
2Writing the formula of ethyl ethanoate incorrectly (e.g., confusing it with other esters).
3Omitting the acid catalyst over the reaction arrow.

Interesting Facts

Esters are widely used in the perfume industry and as artificial flavoring agents in food products like ice creams, sweets, and cold drinks because of their pleasant fruity odors.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2017?

This question carries 3 marks in the CBSE Class 10 Science 2017 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Chemical Properties of Carbon Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2017 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2017 paper.