1、Preparation of Aspirin Purpose of experiment Understand principles and methods of preparation of aspirin Laboratory suppliesAcetic anhydride Salicylic acid Strong phosphoric acid Cold water Ice water Distilled water Graduated cylinder Dryer Distillation flasks Alcohol lamp Tripod Asbestos nets Therm
2、ometer Rubber plugs Condenser tube Rubber hose Horn tube Erlenmeyer flask Glue applicator Beaker Filter paper Buchner funnel Smoke filter Vacuum pump filter Glass rods Pallet scales Experimental principle and stepsStep one : Take 20ml acetic anhydride in the dry distillation of the distillation flas
3、k. Take the steam out of 138 c above the fractions of 6ml and the rest of the collection.As Figure :Phenomena: 136 c began to slip out of the liquid, to 138 c will be able to collect the required fraction.Discussion.: New distilled acetic anhydride, as long the acetic anhydride may contain acetic ac
4、id, will affect the response. The distillation is not using oil-bath heating, oil-bath heating is designed to control temperature, distillation of acetic anhydride is direct to let its temperature rises. Step two : Take 4 grams of salicylic acid in the Erlenmeyer flask placed in a dry, 6ml new disti
5、lled acetic anhydride, and then add 10 drops of concentrated phosphoric acid drops, control heating at 75 c water bath for 20 minutes.After this heat, pour the hot water 5ml, full shock, then poured into the 60ml cold water, in the ice water to cool for 15 minutes and see.Phenomena: Water-bath heati
6、ng finishes, powder reaction of salicylic acid out, only to see the clarification of liquids.Cool in ice water, you can see the solution becomes a white cloudy, with significant crystallization.Chemical equation:Discussion: Concentrated phosphoric acid as a catalyst.Water-bath heating after the hot
7、water 5ml is designed to remove excess acetic anhydride.Because the material is 0.06 mol of acetic anhydride, salicylic acid is 0.03 mol of substance, it is clear that acetic anhydride is excessive, so the water drop.Becomes cloudy and a large number of crystallization, because Aspirin builds.Step t
8、hree: These turbid pour liquid as it cools in place in a Buchner funnel filter paper, cloth under the funnel to pick a filter.Filter received a decompression filter, open decompression filter switch, the pumping filter and observe.50ml distilled water wash each time, then pumping filter, glass rods,
9、 gently stirring constantly.After you finish pumping filter, remember to pull the rubber hose, and then turn off the switch.Phenomena: When the switch is open, fluid flow from the pump filter, with large numbers of crystallization on the filter paper in the funnel.After adding distilled water wash,
10、white cloudy smoke filtered and white Crystal precipitation.Discussion: Final analysis of the pure crystal Aspirin, Aspirin is an anti-inflammatory.Aspirin smoke filters as dry as possible and avoid affecting experimental results.Step four: Aspirin crystals after the filter using filter paper absorb
11、, on the balance on the tray, called a mass of 4.2 grams.Aspirin yieldIn theory, aspirin, salicylic acid should be equal to the amount of material generated by the amount of substance, but the actual yield will be less than the theoretical yield.Last calculated yield of aspirin is 77.78%.After the end of the experiment, recovery of aspirin, finishing experiment equipment.COHOOCH3COHOH + (CH3CO)2O H+ + CH3COH
