LAB 12 Essay examples

Submitted By bloughj
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Pages: 10

LAB# 12
Name: Joy Blough and Jill Smith
Date: 10/24/2013
Instructor: Carrie Salmon, Thursday 7:20pm

PURPOSE: 1) Synthesize aspirin and oil of wintergreen. 2) Use a qualitative test to judge the purity of your prepared aspirin. 3) Calculate a percentage yield for your prepared aspirin. 4) Prepare several fragrant esters


Part A: Synthesis of Aspirin
1. Set up a hot water bath made from a 250ml beaker half full of water and containing 1-2 boiling chips.
2. Use a weighing dish and a centigram or electronic balance to accurately weight out approximately 0.25g of salicylic acid. Record the mass of the salicylic acid sample in Table 12.1 and put the sample into a clean, dry 10cm TT.
3. Heat and stir the water bath until it reaches a temperature of 85-90 degrees Celsius, then remove beaker from heat source.
4. Carefully add 15 drops of acetic anhydride and 2 drops of concentrated sulfuric acid to the salicylic acid sample in the TT and agitate the TT to mix the contents. Put the TT into the water bath.
5. Allow the TT to remain in the hot water bath for 15minutes. Agitate the tube several times during the first 5minutes to make certain all the solid is dissolved. Do not heat the bath during the 15minutes.
6. After the 15minutes, remove the TT from the bath and add 40 drops of ice water, 5 drops at a time, with agitation between each 5-drop addition. After the water addition is completed, put the TT into a mixture of ice and water contained in a small beaker. Allow the TT to cool in the ice-and-water bath for 5 minutes.
7. After 5minutes, remove the TT from the cooling bath and observe its appearance. If you can see distinct crystals of solid forming, put the TT back into the ice-and-water bath for another 5-10minutes. If the TT contents appear uniform and milky, it means your aspirin has not crystallized. Try to get it to crystallize by stirring the mixture with a small spatula or glass stirring rod and, while stirring, scratching the inside surface of the TT with the spatula or stirring rod. Continue this stirring and scratching for a minimum of 5minutes or until the sample begins to crystallize, whichever comes first.
8. If your sample begins to crystallize, return it to the ice-and-water bath stirring and scratching, inform your instructor, who will give you directions for adding a few seed crystals of aspirin to start the crystallization. Once crystallization has been started, return the TT to the ice-and-water bath for 5-10 more minutes of cooling.
9. After the cooling is completed, remove the TT from the cooling bath and centrifuge it to cause the solid to settle. Remember to balance the centrifuge. After centrifuging, decant the liquid from the solid, using a dropper.
10. Wash the solid in the TT by adding 20 drops of ice water and agitating the TT or stirring the mixture until all the solid is suspended. Centrifuge the sample again; decant and dispose of the liquid as you did in Step 9.
11. Accurately weight a clean, dry watch glass on the same balance used in Step 1 and record the mass in Table 12.1.
12. Add 20 drops of ice water to the solid in the tube and agitate or stir the contents to suspend the solid. Quickly pour the suspension out of the TT and onto the watch glass weighed in Step 11. Put the watch glass on top of a boiling water bath and allow it to remain for a minimum of 10 minutes to dry the aspirin you prepared.
13. After the sample has dried for 10 minutes, remove the watch glass and allow it to cool for 2-3 minutes, then dry off the bottom and weigh it on the same balance used in Step 11. Record the combined mass of the watch glass and dried aspirin in Table 12.1. Keep the aspirin for use in Part C.

Part B: Synthesis of Oil of Wintergreen
1. Place 0.1g of salicylic acid into a clean, dry 10cm TT.
2. Add 6 drops of methyl alcohol and agitate the tube until the contents are well mixed.
3. Then add 1 drop of concentrated sulfuric acid.
4. Agitate the tube contents and