sample2-Carbocations+Oxidation+Reflection

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The oxidation of alcohols is a very important reaction in organic chemistry and in biological systems. In organic chemistry lab settings, alcohol oxidation creates very reactive functional groups (aldehydes, ketones, carboxylic acids) that can undergo further reactions and syntheses of organic compounds. In biological organisms, the enzyme alcohol dehydrogenase (ADH) is responsible for catalyzing the oxidation of ethanol so that it doesn’t build up in the blood and poison the organism. This oxidation eventually forms acetic acid, which is a substance that can be metabolized by biological organisms.

From the results obtained by each pair in our group, it is very apparent that the amount of catalyst (e.g. Collins Reagent, or ADH enzyme) is a very important factor in determining the effectiveness of the reaction (the amount of product made and the time it takes to make the product). For example, group 2 (Phoenix and Midori) used PDC and benzyl alcohol. They were able to obtain a pure product of benzaldehyde after refluxing for 35 minutes. The amount of catalyst used was sufficient for the reaction to proceed to completion. On the other hand, after refluxing for 60 minutes, Taylor and Demitri still had a mixture of reactant (benzyhdrol) and product (benzophenone) present. The amount of catalyst used was not sufficient for the reaction to proceed to completion. The solvent chosen for the reaction is also very important. It must be inert and easily removed after formation of product. For example, Erik had to remove the pyridine from his reaction using an acid (HCl). This product has not yet been tested for purity via TLC since there was so little of it; hopefully future IR/NMR analysis can indicate purity of this product. Using dichloromethane as a solvent for the reactions with CrO3/Amberlite, PDC, and Collins reagent proved relatively easy to evaporate, leaving the crystallized product behind.

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This exercise helped the members of our group understand how some catalysts were easier to work with and more effective than others. The catalysts used gave different products and yields. A very similar situation occurs in the human body. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are enzymes used by the body to metabolize alcohol. Research has shown that different people carry different variations of the two enzymes. The variations in enzymes result from variations in the same gene. Since some of these enzyme variants work more efficiently than others, they often influence how much ethanol a person metabolizes. Those that have gene varieties for fast ADH or slow ALDH delay the processing of acetaldehyde in the body. The oxidation of alcohol in the lab is surprisingly not much different than the oxidation of ethanol in the human body so it is a valuable mechanism to understand. ======

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