Organic Chemistry Ii Laboratory
Organic Chemistry II Laboratory (ABCT357)
Although studying fundamental theories of chemistry in the class is important to understand the concept of chemistry, carrying out experiments to corroborate the theories is also important. It is very important for students to get used to experiments in order to speed up their experiments. Expt.1. Acetylation of α-D-glucopyranose
Add slowly 2.5 g (0.014 mol) of powdered D-glucose in small portions (roughly in 7-10 portions and 5 min for each addition) into a preheated solution of ZnCl2 (0.5 g anhydrous ZnCl2 in 12.5 ml acetic anhydride, this will be provided by lab. technician) in a 50 ml pear shape flask (heat in water bath for 10-15 min before addition start). The flask is attached with an air condenser. Swirl the mixture gently during the addition to control the vigorous reaction which ensues. After addition is completed, heat the flask on a water bath for one hour. Cool the content of the flask with cold water, and then pour into ice water (120 ml) and stir vigorously to assist the hydrolysis of unreacted acetic anhydride. After 30 min, the oil which first separates will gradually solidify.* Collect the crude product using Hirsch funnel and record the crude yield of the product. Filter, wash well with cold water and re-crystallize several times from hot methanol/water (3:4) mixture until the mp is constant. Record the melting point. *If solidification is not resulted: Dissolve the oily residue in hot methanol/water (3:4) mixture (heat on steam bath) and then allow it to stand at room temperature for crystals to form. If time is not allowed, label the container for crystallization and hand it in to technician and continue in the next practical class. Question In this experiment, α-D-glucopyranose is obtained. If we use (MeCO)2O/MeCO2Na to react with powdered D-glucose, β-D-glucopyranose will be resulted. Explain.
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Expt. 2. Cis-1,2,3,6-tetrahydro-4,5-dimethylphthalic anhydride (Diels-alder reaction)
Although studying fundamental theories of chemistry in the class is important to understand the concept of chemistry, carrying out experiments to corroborate the theories is also important. It is very important for students to get used to experiments in order to speed up their experiments. Expt.1. Acetylation of α-D-glucopyranose
Add slowly 2.5 g (0.014 mol) of powdered D-glucose in small portions (roughly in 7-10 portions and 5 min for each addition) into a preheated solution of ZnCl2 (0.5 g anhydrous ZnCl2 in 12.5 ml acetic anhydride, this will be provided by lab. technician) in a 50 ml pear shape flask (heat in water bath for 10-15 min before addition start). The flask is attached with an air condenser. Swirl the mixture gently during the addition to control the vigorous reaction which ensues. After addition is completed, heat the flask on a water bath for one hour. Cool the content of the flask with cold water, and then pour into ice water (120 ml) and stir vigorously to assist the hydrolysis of unreacted acetic anhydride. After 30 min, the oil which first separates will gradually solidify.* Collect the crude product using Hirsch funnel and record the crude yield of the product. Filter, wash well with cold water and re-crystallize several times from hot methanol/water (3:4) mixture until the mp is constant. Record the melting point. *If solidification is not resulted: Dissolve the oily residue in hot methanol/water (3:4) mixture (heat on steam bath) and then allow it to stand at room temperature for crystals to form. If time is not allowed, label the container for crystallization and hand it in to technician and continue in the next practical class. Question In this experiment, α-D-glucopyranose is obtained. If we use (MeCO)2O/MeCO2Na to react with powdered D-glucose, β-D-glucopyranose will be resulted. Explain.
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Expt. 2. Cis-1,2,3,6-tetrahydro-4,5-dimethylphthalic anhydride (Diels-alder reaction)