Synthesis of Tetraphenylcylopentadienone
Purpose- This experiment illustrates the use of adol condensation for the synthesis of a five-membered carbocylic ring. It is also a good demonstration of the impact extended conjugation has on the absorption of visible light. The reactants are bright yellow in color while the products are a very deep purple color appearing almost black.
Introduction- The synthesis of Tetraphanylcyclopentadienone was a further example of the adol condensation reaction. Tetraphenylcyclopentadienone was the final product of the three step process shown in earlier experiments. The products that were produced in one experiment were used as the reactants in the next. In the beginning of the adol condensation reactions, we started with Benzaldehyde and through a condensation reaction with cyanide, produces Banzoin. In this experiment, the cyanide ion served three purposes: first of all, it acted as a nucleophile, then it stabilized the intermediate carbanion, and in the end functioned as a leaving group. The Benzoin produced was then in turn purified and used to synthesize Benzil in the next experiment through Copper (II) ion oxidation. The Benzil was obtained by catalytic oxidation of the Benzoin using the Copper (II) ion as the catalytic oxidant. The Benzil produced was then purified and used as the reactants in the third and final experiment of the sequence which was this one, to produce Tetraphenylcyclopentadienone which is a five-membered carboxylic ring. The Benzil was reacted with 1,3- Diphenylacetone to undergo adol condensation and therefore produce Tetraphenylcyclopentadienone. The first step of the reaction to from the Tetraphenylcyclopentadienone requires the loss of -hydrogen to the base, resulting in a negatively charged carbon that bonds with the carbonyl group from the benzil. The bonding then causes the oxygen to become negatively charged and thus an attractant for the adjacent hydrogen,...
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