Recrystalization Lab Report
Recrystallization
Abstract: Technical grade aniline was reacted with acetic anhydride to give acetanilide a dark brown color, due to the presence of impurities. Crystallization of the crude product from water was combined with decolorization with activated carbon, furnished pure acetanilide as white flakes, melting point 112-115°C, yield 70.3%.
Experimental: 2 grams of technical grade aniline and 15ml water were placed in a 125ml Erlenmeyer flask. Then, 2.5ml of acetic anhydride was added while swirling the flask. An exothermic reaction started immediately with concomitant formation of a brown precipitate of crude acetanilide. 50ml of water and a magnetic stirring bar were added to stir the reaction mixture and the flask was heated on a magnetic stirring hot plate until all of the solid and oil were dissolved. The temperature of the reaction mixture at this point was close to 100°C, the boiling point of water. A few milliliters of hot solution was removed from the flask with a disposable pipette and placed in a test tube. The test tube was set aside to cool and produce crystals. The color and melting point of the mini batch of crystals were used to assess the effectiveness of activated carbon treatment of the main batch to remove the colored impurities (vide infra).
The temperature of the main batch of the reaction mixture in the Erlenmeyer flask was brought down to 70-80°C, and approximately a pinch of activated carbon were added to the solution. The reaction mixture was carefully brought to boiling with efficient stirring, to prevent bumping over of the reaction mixture. The hot solution was filtered through a double layer of fluted filter paper arranged in a conical glass funnel, previous heated over a boiling water bath. To complete crystallization, the filtrate was cooled in an ice bath. The crystals were collected by suction filtration. The collected product was spread over a filter paper to dry until the next class period.
Abstract: Technical grade aniline was reacted with acetic anhydride to give acetanilide a dark brown color, due to the presence of impurities. Crystallization of the crude product from water was combined with decolorization with activated carbon, furnished pure acetanilide as white flakes, melting point 112-115°C, yield 70.3%.
Experimental: 2 grams of technical grade aniline and 15ml water were placed in a 125ml Erlenmeyer flask. Then, 2.5ml of acetic anhydride was added while swirling the flask. An exothermic reaction started immediately with concomitant formation of a brown precipitate of crude acetanilide. 50ml of water and a magnetic stirring bar were added to stir the reaction mixture and the flask was heated on a magnetic stirring hot plate until all of the solid and oil were dissolved. The temperature of the reaction mixture at this point was close to 100°C, the boiling point of water. A few milliliters of hot solution was removed from the flask with a disposable pipette and placed in a test tube. The test tube was set aside to cool and produce crystals. The color and melting point of the mini batch of crystals were used to assess the effectiveness of activated carbon treatment of the main batch to remove the colored impurities (vide infra).
The temperature of the main batch of the reaction mixture in the Erlenmeyer flask was brought down to 70-80°C, and approximately a pinch of activated carbon were added to the solution. The reaction mixture was carefully brought to boiling with efficient stirring, to prevent bumping over of the reaction mixture. The hot solution was filtered through a double layer of fluted filter paper arranged in a conical glass funnel, previous heated over a boiling water bath. To complete crystallization, the filtrate was cooled in an ice bath. The crystals were collected by suction filtration. The collected product was spread over a filter paper to dry until the next class period.