To Prepare a Sample of Acetanilide from Aniline

Acetanilide is used to stabilise cellulose ester varnishes and as a hydrogen peroxide decomposition inhibitor. It has also been used as an intermediary in synthesising rubber accelerators, dyes and camphor.

Table of Contents

• Aim of the Experiment

• Apparatus Required

• Theory

• Procedure

• Observations

• Result

• Precautions

Aim of the Experiment

To prepare and submit acetanilide from aniline.

Apparatus Required

• Aniline

• Glacial Acetic Acid

• Acetic Anhydride

• Zinc Dust

• Distilled Water

• Round Bottom Flask

• Beaker

• Pipette

• Reflux Condenser

• Funnel

• Stirrer

• Bunsen Burner

• Filter Paper

• Electronic Balance

Theory

When aniline reacts with acetic anhydride/glacial acetic acid in the presence of zinc dust, acetanilide is formed. To obtain acetic anhydride precipitate, a mixture of aniline, glacial acetic acid, acetic anhydride, and zinc dust is refluxed under anhydrous conditions and then poured into ice-cold water. To obtain pure crystals of acetanilide, the crude precipitate of acetic anhydride is recrystallised. Zinc is used to prevent aniline oxidation in the chemical reaction. Acetanilide has medicinal applications and is used as a febrifuge.

Acetylation of aniline with acetic anhydride in concentrated hydrochloric acid can also yield acetanilide. Dissolve aniline in hydrochloric acid and stir in acetic anhydride. Pour the sodium acetate mixture into the water. Ethyl alcohol can be used to separate and recrystallise acetanilide.

Procedure

• Before beginning the experiment, thoroughly clean the equipment with distilled water.

• Add 10ml aniline, 20ml acetic anhydride, glacial acetic acid mixture, and zinc dust to a round bottom flask.

• With the round bottom flask, secure the reflux condenser.

• In an oil bath, gently heat the mixture for about 15-20 minutes.

• With constant stirring, pour the hot mixture into a beaker containing ice cold water.

• To hydrolyse the excess acetic anhydride, vigorously stir the mixture.

• Once the acetanilide has precipitated, collect it in a Buchner funnel and filter it.

• The precipitate obtained is a crude acetanilide sample. Crystallisation is required to obtain pure crystals.

Observations

Result

The yield of acetanilide is in gm.

Precautions

• Do not breathe acetic anhydride fumes.

• Experiments should always be carried out in a fuming chamber or near a window.

• Reflux the reaction mixture using the water condenser.

• Dry the acetanilide crystals before determining their weight and melting point.

Lab Manual Questions

1. Why is aniline soluble in hydrochloric acid while it is insoluble in water?

Ans. Aniline does not undergo hydrogen bonding because of the presence of benzene, which is highly hydrophobic. therefore aniline is insoluble in water. In the HCl, the amine group becomes protonated ($${{-N}{H}^{3+}}$$) and the ionic hence soluble in HCl.

2. Why is aniline a weaker base than ammonia?

Ans. Since ammonia can easily lose electron pairs while aniline cannot, thus ammonia is a stronger base than aniline.

3. In the preparation of p-nitroacetanilide another minor product is formed. What is this compound, and how can this be separated from p-nitroacetanilide?

Ans. The minor product that is o-nitroacetanilide is separated from the p-nitroacetanilide by dissolving the solution of both products in Ethanol. o-nitroacetanilide is more soluble in alcohol as compared to the p-nitroacetanilide.

4. Is it necessary to recrystallise the compound obtained from the reaction?

Ans. So recrystallisation is important after a compound is obtained from the reaction so that we get pure crystals of our compound and the yield of the compound produced from the reaction can be done accurately without any impurities.

Viva Questions

1. What is the purpose of acetanilide?

Ans. Acetanilide, a synthetic organic compound introduced in therapy in 1886 as a fever-reducing drug. Its effectiveness in relieving pain was discovered soon thereafter. It was used as an alternative to aspirin for many years in treating common complaints such as headaches, menstrual cramps, and rheumatism.

2. Which functional group is present in acetanilide?

Ans. Acetanilide has an amide functional group, meaning it has a nitrogen atom bonded directly to a carbonyl.

3. What is the pH of acetanilide?

Ans. The pH of acetanilide will be between 5 to 7.

4. Why is acetanilide soluble in hot water?

Ans. Because it has a large nonpolar benzene ring, making it insoluble in water at cold temperatures. But, the compound also has an acyl group which is polar. This would make the compound more soluble in water when it is heated.

5. What bonds are present in acetanilide?

Ans. Acetanilide has both sigma and pie bonds. It has 19 σ and 4 π bonds.

6. Is acetanilide soluble in HCl?

Ans. Acetanilide is not soluble in aqueous HCl.

7. What is a good solvent for acetanilide?

Ans. Water is a good solvent for acetanilide.

8. What type of amide is in acetanilide?

Ans. N-phenylacetamide is a member of the class of acetamides that is acetamide in which a phenyl group substitutes one of the hydrogens attached to the nitrogen. It has a role as an analgesic. It is a member of acetamides and an anilide. It is functionally related to acetic acid.

9. How is acetanilide poisoning treated?

Ans. Gently wash all affected skin areas thoroughly with soap and water. If symptoms such as redness or irritation develop, immediately call a physician and be prepared to transport the victim to a hospital for treatment.

10. What is the hydrolysis of acetanilide?

Ans. Crude acetanilide looks like grains of brown rice, while pure acetanilide forms shiny crystals in cold water. The crude solid is dissolved in the smallest possible amount of solvent of choice; in this case, the solvent is water. Acetanilide has a much higher solubility in hot water than in cold water.

Practical Based Questions

1. Aniline is

(a)Acidic

(b)Basic

(c)Neutral

(d)All of the above

Answer: (b)

2. Acetanilide was used as

(a)analgesics

(b)antipyretics

(c)both a and b

(d)None of these

Answer: (c)

3. Technique used to separate aniline from aniline water mixture is

(a)Fractional distillation

(b)Fractional crystallisation

(c)Vaccum distillation

(d)Steam distillation

Answer: (d)

4. The most convenient method to prepare primary amine containing one carbon atom less is

(a) Gabriel phthalimide synthesis

(b) Reductive amination of aldehydes

(c) Hofmann bromamide reaction

(d) Reduction of isonitriles

Answer: (c)

5. Secondary amines can be prepared by

(a) reduction of nitro compounds

(b) oxidation of N-substituted amides

(c) reduction of isonitriles

(d) reduction of nitriles

Answer: (c)

6. Which of the following amides will give ethylamine on reaction with sodium hypobromide?

(a) Butanamide

(b) Propanamide

(c) Acetamide

(d)Benzamide

Answer: (b)

7.The boiling point of acetanilide is

(a)304 degree celsius

(b)316 degree celsius

(c)320 degree celsius

(d)325 degree celsius

Answer: (a)

8. Boiling point of aniline is

(a)183 degree celsius

(b)184 degree celsius

(c)185 degree celsius

(d)184.1 degree celsius

Answer: (d)

9. Melting point of aniline is 

(a)0 degree celsius

(b)-3 degree celsius

(c)-2 degree celsius

(d)-6.3 degree celsius

Answer: (d)

10. Melting point of acetanilide is 

(a)115 degree celsius

(b)113 degree celsius

(c)114 degree celsius

(d)114.3 degree celsius

Answer: (d)

Conclusion

Acetanilide is a colourless, odourless solid chemical that resembles a leaf or flake. It was previously known as Antifebrin and also known as N-phenylacetamide, acetanil, or acetanilid.

Acetanilide is used to stabilise cellulose ester varnishes and as a hydrogen peroxide decomposition inhibitor. It has also been used as an intermediator in the synthesis of rubber accelerators, dyes and dye intermediates, and camphor.

When aniline reacts with acetic anhydride/glacial acetic acid in the presence of zinc dust, acetanilide is formed. To obtain acetic anhydride precipitate, a mixture of aniline, glacial acetic acid, acetic anhydride, and zinc dust is refluxed under anhydrous conditions and then poured into ice-cold water.