High-resolution nuclear magnetic resonance spectra of phenanthrenes—II Halogeno-, cyano-, nitro- and carbonyl phenanthrenes, and phenanthrene-9,10-quinone

Abstract

The 60 Mc/s NMR spectra of 9-fluoro-, 9-chloro-, 9,10-dibromo-, 9-iodo-, 3-acetyl-9-bromo-, 9-cyano-, 9-cyano-10-methyl-, 1-, 2-, 3- and 9-nitro-, 9-bromo-10-nitro-, 2-, 3- and 9-acetyl-, 4- and 9-methoxycarbonyl- and 9,10-dimethoxycarbonyl-, 9-formyl-, 3-ethyl-9-carboxyl-, and 9-phenyl-10-carboxylphenanthrenes have been recorded and analysed, usually as ABX and ABMX, followed by computer refinement. Coupling constants are generally similar to their values in phenanthrene; an inter-ring HF coupling, as well as the expected H(10)F coupling, is observed in the 19F spectrum of 9-fluorophenanthrene. The shift of H(8) in 9-halogenophenanthrenes can be interpreted in terms of magnetic anisotropy and electric field effects, but the H(10) shift is dominated by some factor characteristic of the high C(9)C(10) bond order. Ortho effects of nitro and acetyl also depend on the order of the intermediate bond. The magnetic anisotropy of the cyano group seems to be the largest contributor to the shifts of both H(8) in 9-cyanophenanthrene and CH 3 in 9-cyano-10-methyl phenanthrene. H(9) and H(10) in 3-nitrophenanthrene have sufficiently different shifts to permit measurement of J 9,10. The presence of a 10-substituent greatly reduces the peri effects of nitro and carbonyl groups. By use of the 2,7-dimethyl derivative, the spectrum of phenanthrene-9,10-quinone has been unambiguously assigned.