3 step synthesis of benzylic acid from benzaldehyde

3 step synthesis of benzylic acid from benzaldehyde - Lab 6...

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Lab 6: 3-Step Synthesis of Benzylic Acid from Benzaldehyde Manuel Vazquez 4/29/12
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Introduction: The purpose of this lab was to generate benzylic acid from an original sample of benzaldehyde, going through intermediates of benzoin and benzyl. Although the first step, the conversion of benzaldehyde to benzoin, was provided in the form of the benzoin condensation, the procedures for both the oxidation of benzoin to benzyl and for the benzylic acid rearrangement were to be researched independently from primary sources and selected for the reaction based on their merits. For the benzoin oxidation, there were a plethora of factors to be considered in selecting the reaction procedure to follow, the most important of which was the availability of equipment necessary for its completion; reactions involving column chromatography, irradiation, large insulators, or electromagnetic suspensions were out of the question. Furthermore, the reaction had to run in under 2 hours in order to fit the time restrictions of the lab. The reagents all had to be commercially available, and cheap to make, and had to be relatively non-toxic. Finally, for a reaction to be worthwhile, it needed to have a good yield, which was defined in this experiment as greater than 70%, easily purified product (in other words, easily separable by-products), and preferably would take place in a single step. The ideal reaction fitting this description is describe in Th e Ca t aly t i c Oxida t ion o f B e nzoin t o B e nzil (Weiss et al, 1948). This reaction involves the use of catalytic amounts of copper (II) acetate as the primary oxidizing agent, coupled with the use of NO 3 - to re-oxidize the spent Cu + ions back to the Cu 2+ state, and additionally coupled with the use of the ammonium ion to reduce the resulting NO 2 - to nitrogen gas and water. The mechanism of the copper (II) acetate oxidation of benzoin, in addition to the formulas for the other two reactions, is shown in Figure 1. The mechanism by which copper (I) cation is oxidized is not currently known. For the practical purposes, in this experiment, the reaction was run at ¾ scale of the procedure detailed in the article. In addition to the described procedure, a procedure based on the barium permanganate oxidation described in Firouzabadi et al (1989) was performed as a test to see if the modified reaction was a feasible candidate for future experiments. The particular modifications were made to overcome the obstacles of the unavailability of Ba(MnO 4 ) 2 commercially, and to bypass
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the required column chromatography for separation. To achieve these goals, first, barium permanganate was to be synthesized in s i t u via the reaction of barium manganate and water; VHFRQGO\± WKH HQWLUH UHDFWLRQ ZDV UXQ LQ ZDWHU± UDWKHU WKDQ LQ DFHWRQLWULOH± IRU VLPSOLFLW\¶V VDNH²
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  • Spring '12
  • ProfessorHyatt
  • Biology, Chemical reaction, Benzaldehyde, Benzylic Acid

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