Essay, Research Paper: Recrystallization Of An Impure Compound

Recrystallization Of An
Impure Compound




Lori Benkoski
Organic Chemistry
12-11-97




Purpose/Question: The purpose of this lab is to recrystallize acetanilide by refluxing the substance, filtering it out, and comparing the original mass to the mass of the pure crystals.

Equipment: Buchner Funnel 2.0 g acetanilide
Charcoal filter paper
Boiling chips (Boileezers) filtering flask
reflux condenser iron ring
round bottom flask ring stand/wire gauze
beaker aspirator
clamps large stand
rubber hosing Bunsen burner

Procedure: First attach a clamp to the top of a large stand and clamp on the reflux condenser. Then apply a large rubber stopper to the bottom of the condenser and tightly fit the round bottom flask making sure it is airtight. Clamp the flask securely to the stand and directly below it clamp the iron ring and wire gauze. The Bunsen burner should be placed below the iron ring.
Next, weigh out 2.0g of impure acetanilide. After temporarily removing the reflux condenser, pour in the acetanilide along with two or three boiling chips to the 50ml flask on the reflux apparatus. Now add water into the top of the condenser. Connect the lower rubber hose to the water faucet and lay the upper hose inside of the sink to drain the water. Turn on the water supply, letting it flow at medium speed. Next, bring the solution to a boil making sure the water reflux is a steady drip. After all solids have dissolved and the mixture has cooled for a moment, add a match head sized amount if charcoal and boil for five minutes.
Now attach your filter flask, Buchner Funnel, rubber stopper, and suction tubing and connect this to the aspirator. Place a piece of filter paper (making sure it is a perfect fit) into the funnel and turn on the water supply. Pour preheated water into the funnel to heat it and then discard the water. Then, quickly remove the heated acetanilide solution from its heat source and immediately pour it through the funnel. Transfer filtered solution to a 50ml beaker and allow cooling. Next, remove paper from funnel, clean out all impurities, and add a clean filter paper. After filtered solution has cooled, filter out crystals by suction filtration. Pour cold water over pure crystals. Carefully remove the filter paper and let the crystals dry on a clean piece of filter paper. Let dry overnight.
After scraping dried crystals from the filter paper, weigh the pure acetanilide crystals. Calculate percent recovery.

Data: IMPURE RECRYSTALLIZED

2.0g 0.1g

Calculations: Ea = impure/pure x 100
Ea = 2.0g/0.1g x 100
Ea = 5% (5% recovery)
Conclusion: After close analysis of the obtained data, I have discovered that a major error has occurred somewhere in the procedure of the lab. The results from the calculations for percent recovery show that I have collected a mere 5% of the original sample. Experimental error may have occurred because of many reasons such as: inaccurate measurement, incorrect data, mistake in procedure, problem with condenser of filtering apparatus, etc. In conclusion, despite an obvious error during the lab, the procedure has not only been a great learning experience but also an important lesson on the importance of preciseness when it comes to laboratory science.