Problem

 

In 1900, Gomberg attempted the synthesis of hexaphenylethane by coupling two moles of triphenylmethane in the presence of finely divided zinc. Gomberg observed that the compound A so formed contains only 88% carbon and 6% hydrogen. On carrying out the reaction in an atmosphere of carbon dioxide, he did obtain a compound B with 93.8% carbon and 6.2% hydrogen. Believing it to be his target compound, he dissolved it in benzene, and found that the yellow solution turns colourless when exposed to oxygen. This solution on evaporation yielded the compound A . Gomberg based on these observations proposed the presence of stable triphenylmethyl radicals which then combined in the presence of air to give peroxybis(methanetetrayl)hexabenzene. However, if compound B was indeed hexaphenylethane then the C-C bond was significantly weak compared to other similar compounds. It was only after the study of the spectral pattern of the compound the question of its structure was put to rest (after a period of 60 years). The spectral pattern exihibited 25 aromatic protons and 4 vinylic protons. Suggest a structure for the compound B .

 

Text Books

•  C. M. Loudon , Organic Chemistry , Oxford University Press, 2002, New Delhi.

•  R. R. Morrison, R. N. Boyd and S. K. Bhattacharjee, Organic Chemistry , Dorling Kindersley (India) Pvt. Ltd, 2011, New Delhi.