Diphenylethane, from photolysis

Figure C2.3.9. Product distribution of dissymmetrical ketone photolysis as influenced by cefyltrimethylammonium chloride (CTAC) micelles. The initial ketone, A(CO)B is photolysed to lose the carbonyl group and to produce tliree products, AA, AB and BB. These data are for benzyl (A) 4-methylbenzyl (B) ketone. Product AA is 1,2-diphenylethane, product BB is 1,2-ditolylethane and product AB is l-phenyl-2-tolyl-ethane. At low CTAC concentration, in the absence of micelles, a random distribution of products is obtained. In the presence of micelles, however, the AB product is heavily favoured. Adapted with pennission from 1571.

Homolytic photodissociation of a benzyl-anilino C—N bond has also been observed in a series of iV-(arylmethyl)anilines. The main products identified for 27 are aniline, triphenylmethane and 9-phenylfluorene (28) (equation 4)126. The quantum yields for the formation of Pt C are high (0.6-0.8, 248-nm excitation) and independent of solvent. On the basis of the results of laser flash photolysis and ESR studies, the formation of 28 occurs via the intermediate 29 as a result of electrocyclization of Pt C (Scheme 5). In contrast, the dimerization of the benzyl and diphenylmethyl radicals, leading to the formation of 1,2-diphenylethane and 1,1,2,2-tetraphenylethane, respectively, are efficient in the cases of 30 and 31 (equations 5 and 6)127. In addition, products resulting from the coupling of the photodissociated benzyl and aniline radicals are also observed for 31, presumably due to the less sterically hindered PhCH2 radical when compared with Ph2CH and Ph3C radicals. 

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