Ethanoic Acid

Ethanoic acid (CH₃COOH), commonly known as acetic acid. It is the second member of the carboxylic acid family after methanoic acid. A 5–8% aqueous solution of ethanoic acid is known as vinegar, widely used in households for cooking and preservation.

• Due to its relatively high melting point, pure ethanoic acid solidifies in cold weather, forming ice-like crystals. This form is called glacial acetic acid. The name "glacial" comes from its appearance resembling ice.
• Ethanoic acid contains the carboxyl group (-COOH) as its functional group, which is responsible for its acidic properties and chemical reactivity.

Physical Properties of Ethanoic Acid:

1. Reaction with Sodium Hydroxide (Base): Neutralisation reaction producing a salt (sodium ethanoate) and water:

\[CH_3COOH+NaOH\to CH_3COONa+H_2O\]

2. Reaction with Carbonates/Bicarbonates: Produces carbon dioxide, salt, and water:

\[2CH_3COOH+Na_2CO_3\to2CH_3COONa+CO_2+H_2O\]

\[CH_3COOH+NaHCO_3\to CH_3COONa+CO_2+H_2O\]

3. Esterification Reaction: Reacts with alcohols in the presence of concentrated H₂SO₄ to form esters and water:

\[CH_3COOH+CH_3CH_2OH\xrightarrow{H_2SO_4}CH_3COOCH_2CH_3+H_2O\]

4. Saponification Reaction (Hydrolysis of Ester): When an ester reacts with sodium hydroxide, it forms a sodium salt of a carboxylic acid (soap) and alcohol:

\[RCOOR^{\prime}+NaOH\to RCOONa+R^{\prime}OH\]

Ester+NaOH→Sodium Carboxylate+Alcohol

This process is called saponification and is used for the preparation of soap from fats and oils.

5. Formation of Acid Chlorides: With thionyl chloride (SOCl₂), it forms acetyl chloride:

\[CH_{3}COOH+SOCl_{2}\to CH_{3}COCl+SO_{2}+HCl\]

6. Formation of Acid Anhydrides: Reacts with acetyl chloride to form acetic anhydride:

\[CH_3COOH+CH_3COCl\to(CH_3CO)_2O+HCl\]

7. Reaction with Amines (Amide Formation): Forms amides when reacted with amines:

\[CH_3COOH+NH_2CH_3\to CH_3CONHCH_3+H_2O\]

1. Aim: To compare the acidic strength of ethanoic acid and hydrochloric acid

2. Requirements

Apparatus: Glazed tile, blue litmus paper, pH paper, glass rods
Chemicals: Dilute ethanoic acid, dilute hydrochloric acid

3. Procedure

• Place two strips of blue litmus paper on a glazed tile.
• Use separate glass rods to place a drop of ethanoic acid on one strip and hydrochloric acid on the other.
• Observe the colour change.
• Repeat using pH paper.

4. Observations

5. Conclusion: Ethanoic acid is a weaker acid compared to hydrochloric acid.

1. Aim: To demonstrate the reaction of ethanoic acid with sodium carbonate

2. Requirements

Apparatus: Big test tube, small test tube, thistle funnel, bent gas delivery tube, rubber cork, lime water
Chemicals: Sodium carbonate powder, ethanoic acid, lime water

3. Procedure

• Place sodium carbonate powder in a big test tube.
• Add 10 ml of ethanoic acid through a thistle funnel into the test tube.
• Quickly seal the test tube with a cork fitted with a delivery tube.
• Direct the gas through the delivery tube into another test tube containing lime water.
• Observe the effervescence and change in lime water.

Reaction of acetic acid and sodium carbonate

Reaction:

\[2CH_3COOH+Na_2CO_3\to2CH_3COONa+H_2O+CO_2\uparrow\]

If sodium bicarbonate (NaHCO₃) is used instead:

\[CH_3COOH+NaHCO_3\to CH_3COONa+H_2O+CO_2\uparrow\]

4. Observations

• Effervescence occurs due to the release of CO₂ gas.
• Lime water turns milky, confirming the presence of carbon dioxide.

5. Conclusion: Ethanoic acid reacts with carbonates and bicarbonates to produce a salt (sodium ethanoate), water, and carbon dioxide gas. This is a typical acid-base reaction, and the limewater test is used to confirm the presence of CO₂.

1. Aim: To prepare ethyl ethanoate (an ester) by reaction of ethanoic acid with ethanol

2. Requirements

Apparatus: Test tube, beaker, burner, wire gauze, tripod stand.
Chemicals: Glacial ethanoic acid, ethanol, concentrated sulphuric acid.

3. Procedure:

• Take 1 ml of ethanol and 1 ml of glacial ethanoic acid in a test tube.
• Add a few drops of concentrated sulphuric acid (acts as a catalyst).
• Place the test tube in a hot water bath for 5 minutes.
• After heating, pour the reaction mixture into 20–30 ml of water in another beaker.
• Smell the product carefully.

Esterification Reaction

Reaction:

\[\mathrm{CH_3-COOH}+\mathrm{CH_3-CH_2-OH}\xrightarrow{\mathrm{Conc}\mathrm{H_2SO_4}}\mathrm{CH_3-COO-CH_2-CH_3+H_2O}\]

4. Observation: A fruity, sweet smell is observed due to the formation of ethyl ethanoate.

5. Conclusion: This reaction forms esters, which are compounds known for their pleasant fruity aroma. Esters are widely used in:

• Perfumes
• Flavouring agents
• Fragrances in cosmetics
• Saponification reactions for soap-making

1. It is used in the food industry as vinegar (5–8% solution) for preservation and flavouring in pickles and condiments.
2. Acts as a raw material in the chemical industry for producing esters, polymers, and industrial solvents.
3. Serves as a solvent in laboratories, especially in organic synthesis requiring a polar protic solvent.
4. It is used in pharmaceuticals as an antifungal agent and in drug manufacturing.
5. Participates in esterification reactions to produce esters used in perfumes, cosmetics, and flavourings.
6. Involved in saponification reactions for soap and glycerol production.
7. Forms part of acetate buffer systems to maintain pH in biological and chemical processes.
8. It is used in textile, rubber, plastic manufacturing, surface cleaners, and analytical techniques like titration and chromatography.