Long-range spin-spin coupling in polycyclic hydrocarbons and their derivatives

Abstract Long-range spin-spin couplings have been derived from 60 and 100 Mc/s nuclear magnetic resonance spectra of 9 parent polycyclic hydrocarbons and 26 of their derivatives. Double-resonance experiments were carried out on the following compounds: anthracene (parent, 9-bromo-, and 9-methyl-derivatives); phenanthrene (parent, 1-methyl-, 1-methyl-7-isopropyl-, 3-acetyl-9,10-dimethyl-, 3-acetyl-9-bromo-, 2,7-dimethyl-, 3,6-dimethyl-, 9-methyl-, 9-fluoro-, 9,10 dihydro-, 9-formyl, and 2,2,2-, trimethoxy-4,5-(2,2′-biphenyleno)-1,3,2-dioxaphospholene); triphenylene (parent, 2-methyl-, 1,3-,2,3- and 2,7-dimethyl-, 2,3-dimethoxy-, 1,6,11-, and benz[ a ]anthracene (parent, 7-methyl-, and 7,12-dimethyl-derivatives); 1-methylpyrene; benzo[ c ]phenanthrene; dibenzo[ c , g ]phenanthrene; and fluorene. Measured values of coupling constants are tabulated as benzylic ( ortho , meta , para , or aldehydic) or inter-ring (epi, bay, or peri). A seven-bond methyl-methyl coupling is reported in 7,12-dimethylbenz[ a ]anthracene (estimated at 0·6 c/s) and also in para -methyl-benzylbromide (estimated at 0·4 c/s).