Organic Chemistry lab: Preparation and purification of Aspirin
Question:
1. Explain why and how you need to use the glass rod to promote the crystallization.
2. Which appartus need to be cleaned & dried before use?
3. List possible ecperimental errors that may affect thr product purity.
Please please keep the answers clearly. Thanks a lot.
Experiment A Preparation and Purification of Aspirin AIMS Demonstrate the synthesis of aspirin and recrystallization of aspirin. INTRODUCTION Aspirin Gacetylsalicylic acid) belongs to a class of compounds known as analgesics (painkiller). one of the most widely manufactured drugs in the world. It may be easily It is prepared in the laboratory by heating salicylic acid and acetic anhydride using phosphoric acid as the catalyst. COOH COOH H3PO (CH3CO)20 OCOCH CH,COOH OH Aspirin Salicylic acid Acetic anhydride MATERIALS Salicylic acid, acetic anhydride, concentrated phosphoric acid, 95% ethanol PROCEDURE 1) Add salicylic acid (3 g) in a 125 ml Erlenmeyer flask (conical flask). 2) Demonstrator will distribute acetic anhydride (6 m) to the flask for you. 3) Add concentrated phosphoric acid (5 drops) to the mixture. 4) Swirl the mixture until all the salicylic acid dissolved. 5) Heat the flask on the steam bath for 10 minutes. 6 Allow the mixture cool to room temperature and stir the mixture with a glass rod to promote crystallization. (Record the shape of the crystal) Add water (50 ml slowly to the ice-cold mixture containing the crystals. 8) Separate the crystals by water aspirator using the Buchner funnel. 9 the crystals by sucking air through it. (Save a small amount of sample (1 mg for determining the melting point of the crude sample) 10) Transfer the crystals to a 125 ml Erlenmeyer flask and dissolve the crystals with minimal amount of hot ethanol. (Not more than 8 ml). 11) Add water (25 m) to the alcoholic solution and heat the mixture to almost boiling on a steam bath. 12) Cool the solution at room temperature followed by ice bath and separate the crystals by vacuum filtration and air-dry the crystals by sucking air through it. 13) Dry the crystals in an oven set at 70 oC.
