Tetraphenylcyclopentadienone Lab Report

Synthesis of Tetraphenylcylopentadienone
Post-Lab Report

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
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
I then measured and placed 100 mg (0.10 g) of 1,3-diphenylacetone and 100 mg (0.10 g) of Benzyl into the concial vial. I followed this by placing 0.5 ml of triethylene glycol and then equipped the vial with a condenser as before. The concial vial was then placed in the sand bath on a hot plate stirring and heating at 150-160 degrees Celsius. The reactants were then heated for five to ten minutes. I then removed the apparatus from the heat source and immediately added 100 micro liters of 40% Benzyltrimethylammonium hydroxid-methanol, to the hot reactants inside the concial vial, while gently shaking. As cooling occurred, dark purple (almost black) looking crystals appeared which were the highly conjugated tetraphenylcyclopentadienone. I then obtained the crystals through the use of a Hirsch funnel and vacuum apparatus, and weighed