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C2510_Borohydride_S_2009 - Chemistry 2510 Introduction to...

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Chemistry 2510 Introduction to Experimental Organic Chemistry Spring 2009 Experiment #8 Reaction of Sodium Borohydride with Different Carbonyl Compounds Laboratory Notebook : You need to summarize your experimental plan in your lab notebook. Be sure to include a table of all reagents and compounds that will be used in this experiment. Laboratory Observations: Be sure to record any observations during the laboratory. You must record exactly how much of the starting materials you started with and the weight of the isolated product. Results and Conclusions : Calculate a % yield for the reaction, obtain an IR spectrum of the product and determine the melting point (if solid) of the product. At your discretion, measure the optical rotation of the product. You will attempt to deduce what your starting carbonyl compound was from all of your observations. Relevant Reading: Technique 1, Crystallization, pp 23-38, Technique 2, Melting Points, pp 39-48, Technique 3, Extraction, pp 49-70, Technique 4, Drying Organic Solutions, pp 71-75, Technique 14, Carrying Out Typical Reactions, pp 153-162, Technique 15, IR Spectroscopy, pp 163-178. Background: Reduction of carbonyl groups is an important chemical conversion in organic chemistry. The reduction of these the carbonyl group produces a hydroxyl group. R 1 O R 2 Reduction R 1 OH R 2 + R 1 OH R 2 Reductions can be accomplished by a wide variety of reagents, including hydrogen with an active metal catalyst, sodium borohydride (NaBH 4 ), and lithium aluminum hydride (LiAlH 4 ). These reagents have differing selectivities in terms of which type of carbonyl group they will reduce (i.e. aldehydes, ketones, esters, etc.). If the carbonyl compound is not symmetrical (R 1 and R 2 are not identical), then it is also possible to produce more than one product, depending upon which “face” (a carbonyl group is trigonal planar!) of the carbonyl group the hydride adds to. Each student will get one carbonyl compound (as an unknown) to perform the borohydride reduction with. Using their data and comparing it to other students’ data in the lab, each person will identify their starting compound and their reaction product(s).
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Possible Unknowns . Benzaldehyde, benzoic anhydride, ethyl benzoate, benzophenone are the possible unknown starting carbonyl compounds.
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