Introduction: Nitrous acid (HNO2) is used as a source of nitrosonium ion (N≡O+). The nitrosonium ion by reacting with an aromatic amine converted into a diazonium salt. As diazonium ion is a weak electrophile, it reacts with electron-rich, aromatic coupling agents to produce an azo dye. The products are mainly ortho and para due to the reaction being an electrophilic aromatic substitution
Reaction:
p-nitroaniline p-nitro benzenediazonium chloride Para-red
Procedure:
Production of para-Nitrobenzenediazonium chloride: Prepare 7% NaNO2 by dissolving 7 g of NaNO2 in 100 mL water and in another flask, dissolve 0.4 g of sodium acetate in 3 mL of water. Keep these solutions in ice water bath. Place 0.7 g of p-nitroaniline …show more content…
HCl. Keep the solution in ice water bath.
Part II: Preparation of the diazonium ion Take 5.5 g of p-toluidine into a 100 mL conical flask and add 8 mL water and 6 mL Conc. HCl to it. Stir the solution and heat it until the solid dissolves. Now add 6.5 mL of HCl to this solution. Cool thoroughly in an ice-water bath. In a separate beaker, make up a solution of 3.7 g of sodium nitrite in 10 mL of water. Take a small beaker and weigh out about 5 g of ice and pour it into the conical flask having the reaction mixture. (Ice absorbs the heat released during the formation of diazonium compound. It helps to prevent formation of the undesired phenol side product.) Then pour this solution slowly in the sodium nitrite solution, with vigorous stirring. If the solid doesn’t dissolve within 10 minutes. Add another 0.5 g of sodium nitrite.
Leave the solution in the ice bath.
Part III: Sandmeyer Reaction: Formation of 4-Chlorotoluene Pour the diazonium ion solution (Part 2) into the copper(I) chloride solution (Part 1) and shake the mixture for 5 minutes. Set the system up for a simple distillation. Collect the distillate in a conical flask. Pour your distillate into a separatory funnel. Rinse the conical flask with 15 mL of …show more content…
Add 5.4g (4.5 ml) of benzoyl chloride in two proportions to the solutions. Stopper the flask and shake vigorously after each addition until all the chlorine has reacted. Transfer the solution to a 100 ml beaker and rinse the conical flask with a little water. Place a few grams of crushed ice in the solution and add conc. HCl slowly with stirring until the mixture is acidic to congo red paper. Collect the resulting crystalline precipitate of hippuric acid or benzoyl glycine , which contaminated with a little benzoic acid upon a Buchner funnel, wash with cold water and dry. Place the solid in the 100 ml beaker with 10 ml of CCl4 ,cover the beaker with the watch glass and boil the mixture gently for 5 minutes. Allow the mixture to cool slightly and filter by gentle suction and wash it 3-4 times with CCl4. Recrystallize it from the boiling water.
Mechanism:
The Reaction involves: Nucleophilic attack of NH2 of glucine on the carbonyl carbon of benzoyl chloride Rearrangment and deprotonation (elimination of HCl molecule) to give benzoyl glycine Step II: Preparation of 4-Benzylidine-2-phenyl-oxazol-5-one from benzoyl
Reaction:
p-nitroaniline p-nitro benzenediazonium chloride Para-red
Procedure:
Production of para-Nitrobenzenediazonium chloride: Prepare 7% NaNO2 by dissolving 7 g of NaNO2 in 100 mL water and in another flask, dissolve 0.4 g of sodium acetate in 3 mL of water. Keep these solutions in ice water bath. Place 0.7 g of p-nitroaniline …show more content…
HCl. Keep the solution in ice water bath.
Part II: Preparation of the diazonium ion Take 5.5 g of p-toluidine into a 100 mL conical flask and add 8 mL water and 6 mL Conc. HCl to it. Stir the solution and heat it until the solid dissolves. Now add 6.5 mL of HCl to this solution. Cool thoroughly in an ice-water bath. In a separate beaker, make up a solution of 3.7 g of sodium nitrite in 10 mL of water. Take a small beaker and weigh out about 5 g of ice and pour it into the conical flask having the reaction mixture. (Ice absorbs the heat released during the formation of diazonium compound. It helps to prevent formation of the undesired phenol side product.) Then pour this solution slowly in the sodium nitrite solution, with vigorous stirring. If the solid doesn’t dissolve within 10 minutes. Add another 0.5 g of sodium nitrite.
Leave the solution in the ice bath.
Part III: Sandmeyer Reaction: Formation of 4-Chlorotoluene Pour the diazonium ion solution (Part 2) into the copper(I) chloride solution (Part 1) and shake the mixture for 5 minutes. Set the system up for a simple distillation. Collect the distillate in a conical flask. Pour your distillate into a separatory funnel. Rinse the conical flask with 15 mL of …show more content…
Add 5.4g (4.5 ml) of benzoyl chloride in two proportions to the solutions. Stopper the flask and shake vigorously after each addition until all the chlorine has reacted. Transfer the solution to a 100 ml beaker and rinse the conical flask with a little water. Place a few grams of crushed ice in the solution and add conc. HCl slowly with stirring until the mixture is acidic to congo red paper. Collect the resulting crystalline precipitate of hippuric acid or benzoyl glycine , which contaminated with a little benzoic acid upon a Buchner funnel, wash with cold water and dry. Place the solid in the 100 ml beaker with 10 ml of CCl4 ,cover the beaker with the watch glass and boil the mixture gently for 5 minutes. Allow the mixture to cool slightly and filter by gentle suction and wash it 3-4 times with CCl4. Recrystallize it from the boiling water.
Mechanism:
The Reaction involves: Nucleophilic attack of NH2 of glucine on the carbonyl carbon of benzoyl chloride Rearrangment and deprotonation (elimination of HCl molecule) to give benzoyl glycine Step II: Preparation of 4-Benzylidine-2-phenyl-oxazol-5-one from benzoyl