5-Methoxy, 7-methylbenz[a]anthracene: Crystal Structure of a Planar Weak Carcinogen

Abstract

The crystal and molecular structure of 5-methoxy,7-methylbenz[a]anthracene has been determined by X-ray diffraction at room temperature to an R-index of 0.062 over 936 reflections. The molecule, the first methoxy-substituted methylbenz[a]anthracene to be analysed, is highly planar, with the carbon and oxygen atoms of substituents lying within 0.04 Å of the mean plane of the polycyclic skeleton. Carbon–oxygen bond lengths in the methoxy group are unequal at 1.372(7) and 1.426(9) Å and the C_aromatic–O bond makes dissimilar angles of 113.5(7) and 124.3(7)° at C(5). The shortest C–C bonds are C(5)–C(6) = 1.351(9) at the substituted K-region, C(8)–C(9) = 1.352(9), C(10)–C(11) = 1.362(9) Å, and C(3)–C(4) = 1.361(10) Å. In the unsubstituted bay region, the long beach bond C(13)–C(18) = 1.454(9) Å is flanked by beach bond angles C(12)–C(18)–C(13) = 121.2(6) and C(18)–C(13)–C(1) = 123.1(6)°.