No abstract

No abstract

The synthesis of triangulene (I) was attempted to ascertain whether the hydrocarbon was rendered more stable, than is implied by the diradical formula (I), by a molecular orbital structure with trigonal symmetry. The formula (I) expresses in classical terms that triangulene has no Kekulé structure. Triangulenequinone (XI) was synthesized by two methods and its reduction was studied in detail. The results show that triangulene compounds derived from the skeleton (I) are unstable, immediately polymerizing or rearranging, and that dihydrotriangulene derivatives tend strongly to rearrange to trimethylene compounds.Reduction of di-o-tolylphthalide (II) with zinc and ethanolic potassium hydroxide gave the acid (III) which was condensed to the anthrone (IV) in a sodium chloride-zinc chloride melt at 220°. Mild oxidation of IV with dilute nitric or selenious acid gave the oxanthranol (V) which was further oxidized with nitric acid at 200°under pressure to the dicarboxylic acid (VI). This compound was reduced with zinc dust and sodium hydroxide solution to the dihydroanthracene derivative (VII), the structure of which was established by its absorption spectrum, which is that of a benzene derivative.Oxidation of the phthalide II as described by Ciar and Stewart2 gave the dicarboxylic acid lactone (VIII) in addition to dihydroisobenzofuran-1,3bisspiro-(3-phthalide), formed by rearrangement. When VI or VIII was dissolved in concentrated sulfuric acid and heated with copper powder to 120°, the blue hydroxytriangulenequinone (X) is formed. This compound, the properties of which agreed with those of a sample prepared by Weisz and Korczyn3 by a different method, was found to be so acidic that it dissolved in sodium acetate solution.Triangulene-4,8-quinone (XI), which was formed when VII was treated with concentrated sulfuric acid at room temperature, was also obtained from X by brief reduction in sodium hydroxide solution with zinc dust, followed by reoxidation with oxygen.The absorption spectrum of triangulenequinone is shown in Fig. 1, compared with that of coeran-throne4 to which it is related.When hydroxytriangulenequinone (X) was submitted to the zinc dust fusion procedure of Ciar5 a colorless hexahydrotriangulene (IX) was obtained. Its constitution is readily deduced from its absorption spectrum (Fig. 2) which is of the pure pyrene type and which is closely related to that of 2,3-trimethylenepyrene (XXIV). This compound was prepared from naphtho-(2',7'; l,8)-anthrone (XXIII)6 by means of the zinc dust melt and purified by chromatography. The properties of the hydrocarbon indicate that it had not previously been obtained in a pure state.7

Articles you may be interested inPhotoelectron spectra of polynuclear aromatics. V. Correlations with ultraviolet absorption spectra in the catacondensed seriesThe high-resolution photoelectron spectra of 65 polycyclic aromatic hydrocarbons containing up to II condensed benzene rings have been obtained in the gas phase at temperatures between 20 and 450"C. Vibrational analysis of the spectra coupled with semiempirical MO calculations permitted positive identification of the 71' ionizations in the 6-11 eV range. Irrespective of size and symmetry of the hydrocarbons, two-thirds of all 71' bands are found to precede the onset of (T ionization, which occurs at 1O.6±0.2 eV in the molecules beyond naphthalene. The possibility of lahn-Teller forces operating in the degenerate ionic ground states of D 3h and D 6h molecules is discussed, and comments are made on the origin of the 1350 cm -\ vibrational progression that prevails in the first band of all planar hydrocarbons. In sterically overcrowded systems, excitation of low-frequency twisting and out-of-plane bending modes results in a blurring of the vibrational structure. In cases where reliable x-ray data are unavailable (e.g., dibiphenylene-ethylene), this observation allows a distinction to be made between planar and nonplanar hydrocarbons. The present data are of sufficiently high quality to permit the question as to the planarity of phenanthrene to be settled with some certainty. 12 14 FIG. 4. The photoelectron spectrum of peropyrene (286°).

No abstract