Photochemical Synthesis of Benzopinacol and Its Acid-Catalyzed Rerrangement Product Benzopinacolone
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
Abstract
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 alcohol and through subsequent reactions of radicals it formed two diphenyl ketyl radical which dimerized into benzopinacol. Subsequently, mixture of synthesized benzopinacol, glacial acetic acid and iodine crystal reacted in an acid-catalyzed rearrangement wherein dehydration of benzopinacol resulted into the formation of carbocation. In this state, an aromatic shifted and then, forming delocalized carbocation. Afterward, regenerating the catalyst stabilized the molecule into benzopinacolone. After qualitative and quantitative analysis of the products, it was found out that benzopinacol was successfully synthesized as attested by the IR spectrum which contained OH broad stretch at 3417.86 cm-1-3460.30 cm-1 and overtones at 1800 cm-1-1950 cm-1 region. However, inconsistency was observed in the determined melting point of 200(C-210(C which deviated from theoretical 47.9(C perhaps due to improper use of the apparatus. Conversely, synthesis of benzopinacolone was not a success as there was no drastic change observed in its IR spectrum to that of benzopinacol and deviation on determined melting point from 175(C-177(C to 190(C-197(C which maybe due to incompletion of reaction. Low yields were also obtained after the experiment as only
M.E.G. Balita
Institute of Chemistry, University of Philippines, Diliman, Quezon City
Date Performed: February 18, 2011
Date Submitted: March 4, 2011
Abstract
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 alcohol and through subsequent reactions of radicals it formed two diphenyl ketyl radical which dimerized into benzopinacol. Subsequently, mixture of synthesized benzopinacol, glacial acetic acid and iodine crystal reacted in an acid-catalyzed rearrangement wherein dehydration of benzopinacol resulted into the formation of carbocation. In this state, an aromatic shifted and then, forming delocalized carbocation. Afterward, regenerating the catalyst stabilized the molecule into benzopinacolone. After qualitative and quantitative analysis of the products, it was found out that benzopinacol was successfully synthesized as attested by the IR spectrum which contained OH broad stretch at 3417.86 cm-1-3460.30 cm-1 and overtones at 1800 cm-1-1950 cm-1 region. However, inconsistency was observed in the determined melting point of 200(C-210(C which deviated from theoretical 47.9(C perhaps due to improper use of the apparatus. Conversely, synthesis of benzopinacolone was not a success as there was no drastic change observed in its IR spectrum to that of benzopinacol and deviation on determined melting point from 175(C-177(C to 190(C-197(C which maybe due to incompletion of reaction. Low yields were also obtained after the experiment as only
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