Tetraphenylcyclopentadienone
Introduction
The purpose of this experiment was to synthesize tetraphenylcyclopentadienone by reacting dibenzyl ketone with benzil in the presence of a base. The reaction proceeded via an aldol condensation reaction with dehydration, and then the product crystals were isolated by vacuum filtrations using a Buchner funnel.
Experiment Scheme

Equation 1. Aldol condensation reaction between benzil and dibenzyl ketone in the presence of a base
To begin the experiment 1.5g of benzil, 12mL absolute ethanol and 1.5g of dibenzyl ketone were added to a 50-mL round bottom flask. A stir bar was added and the flask was attached to a condenser and heated in a water bath to 70◦C. The mixture was heated with sitting until the solids dissolved. Once solids were dissolved the temperature was raised to 80◦C with stirring. Using a Pasteur pipet, 2.25mL of ethanolic potassium hydroxide were added drop wise downward through the condenser into the flask. The mixture turned deep purple. After this, the temperature was raised to 85◦C and remained at that temperature with stirring for 15 minutes. After the heating period the flask was removed from the hot water bath and cooled to room temperature. Once at room temperature the flask was placed in ice-water bath for 5 minutes to complete crystallization of product. Using a Buchner funnel we collected the deep purple crystals. The crystals were washed with three 4-mL portions of cold 95% ethanol. The 95% ethanol was also used to rinse out the flask to retain as many crystals as possible. After allowing the crystals to dry some in the Buchner funnel the tetraphenylcyclopentadienone was placed in an oven for 15 minutes to dry. Once the drying time was complete we weighed our product and calculated the percent yield along with the melting point.

Data
Table 1. Chemical table of reagents/products used in experiment.

Table 2. Yield Data.
Discussion
For the aldol condensation reaction to begin the dibenzyl ketone reacts with an OH- base. This first reaction turns dibenzyl ketone into an enolate ion with a carbanion which makes it available to react with benzil. The carbanion attacks the benzil at the Ph-C=O carbon, and this in turn breaks the C=O double bond. This molecule then undergoes a hydration reaction to form the aldol intermediate. The aldol intermediate readily loses water when in the presence of the base OH-. The final reaction turns the aldol intermediate into a ring by an intramolecular aldol condensation reaction followed by a dehydration step and the final product tetraphenylcyclopentadienone is formed. The final product was in crystal form with a sparkly dark purple almost black finish. The percent yield we achieved was 87.59% which is not bad. Our melting point was 224-226oC which is a little higher than the actual melting point 218oC. This could have been caused by impurities in our final product. A low percent yield could have come from not transferring all the crystals from the Buchner funnel to the dish before putting them into the oven. Also the dibenzyl ketone was sticking to the beaker we weighted it out in and thus made it hard to transfer all of it into the 50-mL round bottom flask. Another possible source of error could have come from heating the mixture too quickly and for not enough time. We were having a hard time keeping a constant temperature. When heating the mixture for 15 minutes at 85oC our temperature was around 91oC which may have affected the product formation. Some ways to improve our results would be to heat the mixture at a slower rate. Also monitor the mixture more carefully so that the temperature stays around the desired temperature. Allowing the product to dry longer in the oven could reduce impurities and give a more accurate melting point. Finally making sure all the reactants are in the round bottom flask at the start of the reaction will give a more accurate yield. The goal of the experiment, to synthesize tetraphenylcyclopentadienone, was a success. The combination of our percent yield of 87.59% and a melting point between 224-226oC along with color and state of the products leads me to believe this.
Questions
2.

3. Oxygen (O2) and OH-