Molecular Orbital Theory of Orientation in Aromatic, Heteroaromatic, and Other Conjugated Molecules

Abstract

provided comparisons are made only between closely related compounds. This observation suggests that the central atom is strongly involved in the transition concerned. Although the data presented here are insufficient to make a decision on this point, it is not unlikely that the end absorption corresponds to a dissociation process, as Milazzo has proposed. 7 EXPERIMENTAL All compounds were either obtained from commercial sources or prepared in this laboratory by known THE JOURNAL OF CHEMICAL PHYSICS methods. Commercial samples were purified by recrystallization or distillation. Unless otherwise indicated, the spectra were determined in solution in commercial 95 percent ethanol which was transparent above 210 m,u. A Beckman DU spectrophotometer and 1 em quartz cells were used throughout. The concentrations of the solutions were so chosen as to obtain optical densities between 0.3 and 0.7 at the absorption maxima, and no optical density data below 0.15 were used.

1,3-Dipolar cycloadditions of acridine with nitrile oxides

“…6 The predicted position of electrophilic attack is, on the contrary, at the C-4 position and is in agreement with the experimentally observed products. 13 To the best of our knowledge, however, there are no literature reports concerning cycloaddition reactions of acridine where this acts as a 2π component.…”

The crystal structure of N-[[6-methoxy-5-(trifluoromethyl)thio-1-naphthalenyl]thioxomethyl]-N-methylglycine, C16H14F3NO3S2

“…Electrophiles tend to approach S roughly 20" from the perpendicular to the plane through atoms Y-S-Z, with values ranging from 0" to 40". In terms of the "frontier orbital" model (14,15), this direction corresponds to the highest occupied molecular orbital (HOMO), which is a sulfur lone-pair orbital. Nucleophiles, on the other hand, were shown to approach the sulfur atom approximately along the extension of one of the two covalent bonds to S , which was identified as the lowest unoccupied molecular orbital (LUMO), the antibonding orbital, a*.…”

Electron Spin Resonance Absorption Spectrum of Pummerer's Oxygen Radical

“…I t is suggested that the radical is highly distorted by steric hindrance and the distribution of the unpaired electron is restricted to the naphthalene nucleus to which the peroxide oxygen atom is attached. By the simple LCAO-MO method, the density of the frontier electrons, i.e., the electrons in the highest occupied energy level, in P-substituted naphthalene was calculated by Fukui et al (4). Based on their result, the protons which contribute to the hyperfine splitting can be assigned to those attached to the starred carbon atoms in (111).…”