Essay about Photochemical Synthesis of Benzopinacol and Its Acid-Catalyzed Rerrangement Product Benzopinacolone

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Photochemical Synthesis of Benzopinacol and its Acid-Catalyzed Rerrangement Product Benzopinacolone

M.E.G. Balita
Institute of Chemistry, University of Philippines, Diliman, Quezon City
Date Performed: February 18, 2011
Date Submitted: March 4, 2011
In this experiment it is aimed to synthesize benzopinacol through photochemical reaction of benzophenone and, benzopinacolone via acid-catalyzed rearrangement of benzopinacol. In this experiment, mixture of benzophenone, isopropyl alcohol and a drop of glacial acetic acid was exposed to sunlight which in turn, undergone photochemical reaction. In this reaction, molecules of benzophenone was brought to n((* triplet state where it possibly abstracted hydrogen from isopropyl
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The solution was then heat to dissolve benzopinacol and further heated for 5 minutes. After a stiff paste product formed, the reaction mixture was cooled to room temperature. The crystalline mass that formed was subsequently reduced to pieces. Using a little ethanol, the paste was thinned. The mixture was then centrifuged and the supernant was decanted leaving the solids in the test tube. Another two centrifugations were performed, note that, small amount of ethanol was added after each decantation. The product formed was then transferred to a filter paper by resuspending the solids in a little cold ethanol. Then, it was filtered through suction. It was subsequently crystallize by dissolving the filtered solids in a 5ml of 2:1 mixture of toluene and hexane in a pre-weighed vial. The vial was covered with aluminum foil with holes and was left in the fume hood to dry the product. Its melting, yield and infared spectrum was obtained the next meeting.

III. Results and Discussion

In this experiment, it is aimed to synthesized benzopinacol from benzophenone via photochemical reaction and benzopinacolone through acid-catalyzed rearrangement. In the synthesis of benzopinacol, benzophenone underwent photochemical reaction. Here, the starting material was exposed to sunlight which supplied enough energy to excite its molecules. Benzophenone upon absorbing light, undergone a rapid intersystem crossing of n((* singlet state to an energetically close (((*