need a good hypothesis for this experiment EXPERIMENT 8 REDUCTION OF A KETONE In

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need a good hypothesis for this experiment

EXPERIMENT 8 REDUCTION OF A KETONE Introduction form C-Z bo reactions are used in many applic vitamin A to name a few. In this experiment, you will be using a reducing agent, Reduction reactions are a result of an electron transfer, where the reactant gains electrons to the product. In organic chemistry, reduction reactions result in a decrease in the number of nds (usually C-O bonds) and an increase in the number of C-H bonds. These types of ations including the synthesis of various antibiotics, steroids, and sodium de, to reduce a ketone, benzophenone, to form an alcohol, biphenylmethanol (or diphenylmethanol), as shown in Figure 1. Figure 1: Reduction of benzophenone to biphenylmethanol using sodium borohydride 4 Na+ BH4 4 95% Ethanol sodium borohydride diphenylmethanol Reaction mechanism The reduction reaction occurs by a two-step process beginning with a nucleophilic attack, followed by protonation, shown in Figure 2. In step one of the reaction, the nucleophile, BH donates H: to the carbonyl carbon. It should be noted that H: does not exist in solution, instead it comes from the B-H bond as shown in the reaction (Figure 2). In BH, boron has a negative formal charge and when H: is donated to the carbonyl, the borohydride compound forms BH3 with no charge. When the H: is donated, the pi bond of the carbonyl cleaves and the electron pair moves to the oxygen, forming an alkoxide and a new C-H bond (Figure 2). In step two of the

Explanation / Answer

Reduction reactions are important in organic synthesis as they have been utilized in the synthesis of various natural products and pharmaceutical drugs. Reduction reactions involve the removal of the hydrogen and the addition of the hydrogen. one such example of a reagent which is used to carry out reduction reaction is sodium borohydride which reduces carbonyl group to the alcohol. The starting material is the ketone known as benzophenone which is reduced to an alcohol called as diphenylmethanol. The mechanism involves the transfer of the hydride from BH4- ion to the carbonyl group of the benzophenone resulting in the formation of an intermediate alkoxide which is subsequently quenched by water to give the product diphenylmethanol. Sodium borohydride is the preferred choice for reduction as it is mild in nature and selectively reduces aldehydes and ketones in presence of other functional groups. The reaction is monitored through a technique known as thin layer chromatography where the starting material and reaction mixture is spotted on a TLC plate using 5% ethyl acetate and hexane to monitor the progress of the reaction until complete disappearance of the substrate and the formation of the product. The pure product will only show one spot in the TLC plate which marks the end of the reaction. The isolated product after the reaction workup is air dried and weighed to record the mass which will provide the percent yield. The product is characterized by melting point and by a spectroscopic technique known as IR which will give information about the functional groups resent in the product.

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