Synthesis of Methyl Orange
Objective
To synthesis methyl orange by coupling diazotised sulphanilic acid with N,N-dimethylaniline.
Materials (Chemicals)
Sulfanilic acid, 2.5% aqueous sodium carbonate solution, sodium nitrite, concentrated hydrochloric acid, N,N-dimethylaniline, glacial acetic acid, 10% aqueous sodium hydroxide, saturated sodium chloride solution
Apparatus
50 mL Erlemeyer flask, 250 mL beaker, test tube, hot plate, Buchner funnels
Procedure In a 50 mL Elermenyer flask 1.2 g of sulfanilic acid and 12.5 mL of 2.5% aqueous sodium carbonate solution was placed. The flask was warmed on a hot plate until the sulfanilic acid dissolved. The solution was then cooled under a tap water. Followed by adding 0.48 g of sodium nitrite to the solution and the solution was stirred until the sodium nitrite dissolved. Then, the solution was poured into a 250 mL beaker that contained 7.5 g of ice and 1.3 mL of concentrated hydrochloric acid in where a white-orange fine-powdered precipitate was formed. 1.0 mL of N,N-dimethylaniline and 1.0 mL of glacial acetic acid was mixed in a test tube. The solution of N,N-dimethylaniline acetate with stirring was added to the suspension of diazotized sulfanilic acid. The test tube was rinsed with a small amount of water which was then added to the beaker. The solution was thoroughly and a red paste was separated from the rest of the solution in about 5 minutes. 10 mL of a 10% aqueous sodium hydroxide was added to the solution to create the orange sodium salt. The mixture was stirred and heated to its boiling point. The solution was let to cool and the beaker was placed in ice water. The product was collected using vacuum filtration and Buchner funnel. The flask and filter cake was rinsed with saturated sodium chloride solution. The percentage yield was calculated.
Results
Colour of compound: Brown
Percentage yield
1.2g 1.0g
No of mole of N,N-dimethylaniline = 1.0 ÷ 121.18 = 8.25 × 10-3mol
1 mol N,N-dimethylaniline → 1 mol
To synthesis methyl orange by coupling diazotised sulphanilic acid with N,N-dimethylaniline.
Materials (Chemicals)
Sulfanilic acid, 2.5% aqueous sodium carbonate solution, sodium nitrite, concentrated hydrochloric acid, N,N-dimethylaniline, glacial acetic acid, 10% aqueous sodium hydroxide, saturated sodium chloride solution
Apparatus
50 mL Erlemeyer flask, 250 mL beaker, test tube, hot plate, Buchner funnels
Procedure In a 50 mL Elermenyer flask 1.2 g of sulfanilic acid and 12.5 mL of 2.5% aqueous sodium carbonate solution was placed. The flask was warmed on a hot plate until the sulfanilic acid dissolved. The solution was then cooled under a tap water. Followed by adding 0.48 g of sodium nitrite to the solution and the solution was stirred until the sodium nitrite dissolved. Then, the solution was poured into a 250 mL beaker that contained 7.5 g of ice and 1.3 mL of concentrated hydrochloric acid in where a white-orange fine-powdered precipitate was formed. 1.0 mL of N,N-dimethylaniline and 1.0 mL of glacial acetic acid was mixed in a test tube. The solution of N,N-dimethylaniline acetate with stirring was added to the suspension of diazotized sulfanilic acid. The test tube was rinsed with a small amount of water which was then added to the beaker. The solution was thoroughly and a red paste was separated from the rest of the solution in about 5 minutes. 10 mL of a 10% aqueous sodium hydroxide was added to the solution to create the orange sodium salt. The mixture was stirred and heated to its boiling point. The solution was let to cool and the beaker was placed in ice water. The product was collected using vacuum filtration and Buchner funnel. The flask and filter cake was rinsed with saturated sodium chloride solution. The percentage yield was calculated.
Results
Colour of compound: Brown
Percentage yield
1.2g 1.0g
No of mole of N,N-dimethylaniline = 1.0 ÷ 121.18 = 8.25 × 10-3mol
1 mol N,N-dimethylaniline → 1 mol