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10 Nov 2019
In IR and NMR spectra, how would you know if unreacted benzaldehyde was a contaminate in your product?
Experiment 8 The Aldol Condensation: Preparation of Dibenzalacetone Objectives Carry out a mixed aldol condensation between acetone and benzaldehyde. Characterize the product using IR and NMR spectroscopy, and melting point. Use proton NMR coupling constants to determine double bond configuration. NaOH Adapted from Williamson, Kenneth L. and Masters, Katherine M., Macroscale and Microscale Organic Experiments, 6th edition. Belmont, CA: Brooks/Cole, 2011, pp486-7. Procedure Twenty-five mL of a 1.25 M solution of NaOH in aqueous ethanol (provided) is placed in a 125 mL Erlenmeyer flask along with a 1-inch magnetic stirring bar and a thermometer. The solution is stirred while the calculated volume of benzaldehyde is added. (Note temperature and other changes.) The calculated volume of acetone is then added and the mixture is stirred for 30 minutes. Water (10 mL) is added to the reaction mixture and the solid product is isolated by vacuum filtration on a Buchner funnel. The solid is washed three times with 25 mL portions of water and air dried for several minutes. A small amount of solid is placed in an open test tube for melting point analysis and the remainder is recrystallized from 95% ethanol. (while crystallizing is taking place, the contents of the filtration flask are transferred into the appropriate aqueous waste container. The flask is rinsed with water and the Buchner funnel is rinsed with acetone.) The recrystallized product is collected by vacuum filtration and washed with a small amount of chilled 95% ethanol. The crystals are air-dried until the next lab period and characterized by melting point (on crude and final product), and IR and NMR spectroscopy. The coupling constant, J, for the alkenyl protons is determined using the appended instructions.
In IR and NMR spectra, how would you know if unreacted benzaldehyde was a contaminate in your product?
Experiment 8 The Aldol Condensation: Preparation of Dibenzalacetone Objectives Carry out a mixed aldol condensation between acetone and benzaldehyde. Characterize the product using IR and NMR spectroscopy, and melting point. Use proton NMR coupling constants to determine double bond configuration. NaOH Adapted from Williamson, Kenneth L. and Masters, Katherine M., Macroscale and Microscale Organic Experiments, 6th edition. Belmont, CA: Brooks/Cole, 2011, pp486-7. Procedure Twenty-five mL of a 1.25 M solution of NaOH in aqueous ethanol (provided) is placed in a 125 mL Erlenmeyer flask along with a 1-inch magnetic stirring bar and a thermometer. The solution is stirred while the calculated volume of benzaldehyde is added. (Note temperature and other changes.) The calculated volume of acetone is then added and the mixture is stirred for 30 minutes. Water (10 mL) is added to the reaction mixture and the solid product is isolated by vacuum filtration on a Buchner funnel. The solid is washed three times with 25 mL portions of water and air dried for several minutes. A small amount of solid is placed in an open test tube for melting point analysis and the remainder is recrystallized from 95% ethanol. (while crystallizing is taking place, the contents of the filtration flask are transferred into the appropriate aqueous waste container. The flask is rinsed with water and the Buchner funnel is rinsed with acetone.) The recrystallized product is collected by vacuum filtration and washed with a small amount of chilled 95% ethanol. The crystals are air-dried until the next lab period and characterized by melting point (on crude and final product), and IR and NMR spectroscopy. The coupling constant, J, for the alkenyl protons is determined using the appended instructions.
Elin HesselLv2
29 Jul 2019