Publication costs assisted by E, I. du Pont de Nemours and Company New values of -core charges for atoms in and about the nitro function have been extracted from the valence-electron densities recently defined by CNDO and ab initio calculations on nitromethane, and by the CNDO analysis of nitrobenzene. With the new -core charge values of nitrogen equals 1.5, oxygen equals 1.2, and the sp2 carbon bearing the nitro function equals 1.1 electron units, and using the method of Nishimoto and Forster, PPP-CI calculations have been made on a representative sample of nitroaromatic species. For the first time, the calculated -electronic spectral features and dipole moments for nitrobenzene, the dinitrobenzenes, and s-trinitrobenzene correspond in a predictively useful manner to the values of observation. The atomic point charge densities determined for nitrobenzene and 7V,jV-dimethyl-p-nitroaniline support the suggestion of Nagakura, et al., that the unusually long C-N bond length in nitrobenzene can be attributed to electrostatic repulsion between positive charges on these bonding atoms.
(1)H, (19)F, (13)C, (15)N, and (17)O NMR chemical shifts and (1)H-(1)H, (1)H-(19)F, (1)H-(13)C, (19)F-(13)C, and (19)F-(15)N coupling constants are reported for 2-(trifluoromethyl)-2-oxazoline.
Molecular orbital spectral predictions suggest that 2,5,7,10,12,15,17,20-octaaza-21H, 23H-porphine has a visible spectral range closely matching that of chlorophyll-a. Since the octaazaporphine is, in its core, a simple derivative of an (HCN)12 oligomer, this fact, together with its spectral properties, would suggest that it occupies a high rank as a primordial porphinic solar energy transducer for photochemistry essential to life's formation. The demonstration that the mass 324 hexahydrooctaazaporphine is formed in protic media by the cyclotetramerization of imidazol-4-aminohydroxonium ion or the derived nitrenium ion, and that a mass 318 species consonant with that of the Huckel aromatic octaazaporphine is observed in the course of these studies, strongly supports the proposed octaazaporphine synthesis in a prebiotic hydrocyanic acid milieu.
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