26 Synthesis of Aspirin - S (page 3 of 8) Q Search Procedure Preparation of Aspi

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26 Synthesis of Aspirin - S (page 3 of 8) Q Search Procedure Preparation of Aspirin I. Prepare a hot water bath for use in step 5 and add a boiling stone. See Figure2. Heat the water to about N0°C. Ringsand 2. Tare (ero) a clean 50-ml Erlenmeyer flask and adld aout 0.5 g of salicylic acil. Measure and recond the precise mass of salicylic acid to 001 g Working in the hood, add 1 ml. of acetic anhydride to the Edenmeyer flask using a graduated Beral-type pipet Carefully add 2 drops of concentrated salfuric acid to the flask Hot water 5. Place the flask in a clamp and att h de clanip to the riesg stand. Beaker Carefully lower the Erlenmeyer dask into the hot water badL IbK the reaction msture for 10 minates 6 Halt-fill a 250-mL beaker with crushed ice and water for use as Hot plate an ice bath. Obain about 15 ml. of distilled water in a small bea- ker or test tube and cool the water in the ice bath Figure 2 .After 10 minutes,carefully lift the Edenmeyer ask out of the hot water bath and allow to cool. H Add 3 ml. of ice-cold water dropwise to the reaction mixture Heany rubbar Tubing with pinch clamp Note: Water may react vigorously with acetic anhydride to fo acetic acid. Awoid breathing the vapor 9. Add an additional $-6 ml. of ice-cold water to the flask, and place the flask in the ice bath to crystallize the aspirin IE no crystals have formed after 5 minutes, gently scratch the sides of the lask with a stirring rod 10. Keep the flask in the ice bath for 10 minutes to complete crystal I1. Measure and record the mass of filter paper and set up a vacam l tilter flask is ltration apparatus as shown in Figure 3. The used as a trap to prevent back up of water lask when the vacuum isreleased. lter flasks Figure 3 12. Isolate the precipitate by vacuum filtration. Careful transfer tech- 13. Rinse any remaining crystals from the flask into the Büchner funnel with a small amount (no more than 4 mL) of 14. Measure and record the mass of a clean and dry watc h glass. Dry the aspirin under vacuam. Then carefully remove 15. Measure and record the combined mass of the watch glass, filter paper and aspirin product niques are essential for accurate resules. ice-cold water. the filter paper and crytals, and place them on the watch glass. Allow the crystals to air dry for 10 minuts Laberatory Experiments far General, Orgic and Bilogical Chemsty3

Explanation / Answer

Ans. #1. A substance that triggers “tear flow” when exposed to eye.

Wear safety goggles whiles working with acetic acid.

#2. Sulphuric acid acts as catalyst for the reaction.

Hazards: Highly corrosive to skin and all tissues. Corrosive to clothes. Burns tissue when comes in contact.

#3. #a. Molar mass of salicylic acid = 138.12 g/ mol

# Molar mass of acetic anhydride = 102.09 g/ mol       

#b. Moles of salicylic acid added = Mass / MW = 0.5 g / (138.12 g/ mol)

= 0.00362 mol

# Mass of acetic anhydride = Vol x Density = 1.0 mL x (1.08 g/ mL) = 1.08 g

Moles of acetic anhydride = 1.08 g / (102.09 g/ mol) = 0.01058 mol

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