Studies in photochemistry. Part VIII. The ultraviolet, proton magnetic resonance, and mass spectra, and photocyclisation of some styrylnaphthalenes to some benzo[c]phenanthrenes and chrysenes
Kinetic data for the first-order ring opening of the dihydro-intermediates, formed on the photocyclisation of several styrylnaphthalene analogues, are presented and some aspects of their electronic spectra are discussed. The photocyclodehydrogenation of 1,2-di-(2-naphthyl)ethylene to benzo[g,h,i]perylene proceeded via dibenzo[c,g]-phenanthrene. Photocyclodehydrogenation of 2-methyl-1-(2,4,6-trimethylstyryl)naphthalene, 2-methyl-1-styrylnaphthalene, 1-(2,4,6-trimethylstyryl)naphthalene, and 1-(2,6-dichlorostyryl)naphthalene yielded the expected chrysene derivatives. 1-Bromo-2-styrylnaphthalene and 2-(2,4,6-trimethylstyryl)naphthalene photocyclised to benzo[c]phenanthrene and 2,4-dimethylbenzo[c]phenanthrene respectively. No migration of substituents was observed. The effect of electron impact on these styrylnaphthalenes correlates with their photochemical behaviour. The u.v. and 1H n.m.r. spectra of the styrylnaphthalenes are discussed.