| Aim | Preparation of Organic CompoundsPreparation of any one of the following compoundsi) Acetanilide ii) Di -benzalAcetone iii) p-Nitroacetanilide iv) Aniline yellow or 2 – Naphthol Anilinedye. |
| Apparatus Required | Materials required for Preparation of Acetanilide Aniline Acetic anhydride Distilled water Sodium hydroxide Buchner funnel Filter paper Vacuum pump Materials required for Preparation of Di -benzalAcetone Benzaldehyde Acetone Sodium hydroxide Ethanol Buchner funnel Filter paper Vacuum pump Materials required for Preparation of p-Nitroacetanilide: Acetanilide Nitric acid (concentrated) Sulfuric acid (concentrated) Ice Water Sodium bicarbonate Buchner funnel Filter paper Vacuum pump Materials required for Preparation of Aniline yellow or 2 – Naphthol Anilinedye Aniline 2-naphthol Hydrochloric acid (concentrated) Sodium hydroxide (concentrated) Ethanol Buchner funnel Filter paper Vacuum pump |
| Theory | i) Preparation of Acetanilide: Acetanilide can be prepared by acetylation of aniline with acetic anhydride. The reaction can be represented as follows: Aniline + Acetic anhydride → Acetanilide + Acetic acid The reaction is usually carried out in the presence of a catalyst like phosphoric acid, which helps in the formation of the acetylating agent, acetyl phosphate. The reaction mixture is heated under reflux for a few hours, and the product is isolated by filtration and recrystallization. ii) Preparation of Di-benzalAcetone: Di-benzalAcetone can be prepared by the Claisen-Schmidt condensation reaction between two molecules of benzaldehyde and one molecule of acetone. The reaction can be represented as follows: 2 Benzaldehyde + Acetone → Di-benzalAcetone The reaction is usually carried out in the presence of a base like sodium hydroxide, which helps in the deprotonation of the carbonyl compounds and promotes the condensation reaction. The reaction mixture is heated under reflux for several hours, and the product is isolated by filtration and recrystallization. iii) Preparation of p-Nitroacetanilide: p-Nitroacetanilide can be prepared by nitration of acetanilide with a mixture of nitric acid and sulfuric acid. The reaction can be represented as follows: Acetanilide + HNO3/H2SO4 → p-Nitroacetanilide + H2SO4 + H2O p-Nitroacetanilide is an organic compound that is used as an intermediate in the synthesis of other organic compounds. It is prepared by the reaction of p-nitroaniline and acetic anhydride in the presence of a catalyst. The reaction is an example of an acylation reaction, where an acyl group is transferred to a molecule. (iv) Aniline yellow or 2-Naphthol Aniline dye is a yellow azo dye that is commonly used in the textile industry. The dye is prepared by a reaction between aniline and 2-naphthol in the presence of a diazonium salt. The overall reaction for the preparation of Aniline yellow is as follows: Aniline + 2-Naphthol → Aniline yellow The reaction is carried out in the presence of a diazonium salt. The diazonium salt is formed by reacting aniline with nitrous acid, which is generated in situ by the reaction of sodium nitrite with hydrochloric acid. The reaction of aniline with nitrous acid forms a diazonium salt intermediate, which is then reacted with 2-naphthol to form the final product. The general reaction for the formation of a diazonium salt is as follows: Aniline + Nitrous acid → Diazo compound The diazonium salt can then be reacted with a suitable coupling agent, such as 2-naphthol, to form the azo dye. The general reaction for the formation of an azo dye is as follows: Diazo compound + Coupling agent → Azo dye The chemical formula for Aniline yellow is C16H13N3O. |
| Procedure | (i)Procedure preparation of Acetanilide In a 250 mL round bottom flask, mix 20 mL of aniline with 30 mL of acetic anhydride. Heat the mixture on a water bath for 10-15 minutes, until the reaction is complete. Stir occasionally. Cool the mixture to room temperature and then pour it into a beaker containing 300 mL of distilled water. The precipitate of acetanilide will form. Filter the precipitate through a Buchner funnel using a vacuum pump. Wash the acetanilide with cold water and then with a sodium hydroxide solution to remove any remaining aniline. Dry the acetanilide in an oven at 60°C. (ii)Procedure preparation of Di -benzalAcetone In a 250 mL round bottom flask, mix 10 mL of benzaldehyde with 20 mL of acetone. Add a few drops of sodium hydroxide and heat the mixture under reflux for 2-3 hours. Cool the mixture to room temperature and then pour it into a beaker containing 200 mL of distilled water. The precipitate of di-benzalacetone will form. Filter the precipitate through a Buchner funnel using a vacuum pump. Wash the di-benzalacetone with ethanol and then dry it in an oven at 60°C. (iii)Procedure preparation of p-Nitroacetanilide In a small beaker, add 5 g of acetanilide and 7 mL of concentrated nitric acid. Stir the mixture gently. In a separate beaker, mix 8 mL of concentrated sulfuric acid and 15 mL of water. Add ice to cool the mixture. Slowly add the acetanilide-nitric acid mixture to the sulfuric acid-water mixture while stirring. Keep the temperature below 10°C by adding ice as needed. After all the acetanilide-nitric acid mixture has been added, stir the mixture for an additional 10 minutes. Pour the reaction mixture into a beaker containing 100 mL of water and stir to precipitate the p-nitroacetanilide. Filter the precipitate through a Buchner funnel using a vacuum pump. Wash the p-nitroacetanilide with cold water and dry it in an oven at 60°C. Procedure for preparation of Aniline yellow or 2 – Naphthol Anilinedye In a small beaker, mix 2 g of aniline and 3 g of 2-naphthol with 5 mL of concentrated hydrochloric acid. Heat the mixture to 70°C for 10 minutes, stirring occasionally. Cool the mixture to room temperature, and then slowly add 10 mL of concentrated sodium hydroxide while stirring. The mixture will turn yellow. Filter the precipitate through a Buchner funnel using a vacuum pump. Wash the dye with ethanol and dry it in an oven at 60°C. |
| Observation and Result | i) Preparation of Acetanilide: Observations: The reaction mixture becomes thick and yellowish. The solution becomes clear after pouring into water. A white solid precipitate forms after filtering the mixture. Result: Yield: Around 5 g of acetanilide Physical properties: White solid, melting point 114-116°C. ii) Preparation of Di-benzalAcetone: Observations: The reaction mixture turns yellow and becomes viscous. The precipitate forms after pouring into water. The precipitate has a yellow color. Result: Yield: Around 3 g of di-benzalacetone Physical properties: Yellow solid, melting point 110-112°C. iii) Preparation of p-Nitroacetanilide: Observations: The reaction mixture becomes yellowish-brown as nitration occurs. The mixture generates a gas (nitrogen dioxide) during the reaction. A yellow solid precipitate forms after adding the reaction mixture to water. Result: Yield: Around 5 g of p-nitroacetanilide Physical properties: Yellow solid, melting point 215-218°C. iv) Preparation of Aniline yellow or 2-Naphthol Aniline dye: Observations: The mixture turns yellow after adding sodium hydroxide. A yellow precipitate forms after filtering the mixture. The dye dissolves in ethanol. Result: Yield: Around 2.5 g of Aniline yellow or 2-Naphthol Aniline dye Physical properties: Yellow solid, soluble in ethanol. |