Anthracenium ion

It was also possible to prepare stable ethylene-(4-X)-naphthalenium ions 115 (X= Me, Ph, OMe) and 9,9-ethylene-(10-X)-anthracenium ions 116 (X = H, Br) under long-lived stable ion conditions114. 

Since the postulation of the anthracenium ion, 2, several intermediates of similar structure, e.g., 3 and 4, have actually been isolated at low temperatures 17) ... 

Molecules of aromatic compounds normally contain several non-equivalent ring carbon atoms, hence in general the protonation must lead to an equilibrium mixture of isomeric arenium ions. As a rule, however, the equilibrium is sharply shifted to the side of one or two isomers only the most stable ions are detected by the NMR spectra. For example, when anthracene is protonated the 9-H-anthracenium ion is the only one observed. 

Quite a few ions of the anthracenium series have been described. For the unsubstituted 9-H-anthracenium ion the recording of the PMR spectrum at 300 MHz has made it possible to determine the chemical shifts of all protons... 

The data on anthracenium ions containing substituents in the 9- and 10-positions are collected in Table 8. The proton chemical shifts of anthracenium ions are influenced by the partial transfer of the positive charge to the side rings and by the effect of magnetic anisotropy of the entire ring system. To illustrate the latter note an... 

On the described basis -li3c i were used to indicate the valent state of the carbon atom in arenium ions and their analogues. Thus, a comparison of Ji3 i for anthracene, 9-H-anthracenium ion and diphenylmethane has supported the assumption that on protonation of anthnu e the carbon atom capturing the proton passes from the sp state into the sp type. 

The NMR- C spectra of anthracenium ions are presented in Table 29. The spectra of 9-R-9,10-dimethylphenanthrenium ions (R=CHj, C Hj, p-CHjC H, p-QC H, p-FCgH and p-CFjCgH j) are also analysed Cited below are the data for R=CH332 (HSO3F, -70 °C). 

The NMR- F spectra of polyfluorinated 1- and 2-hydroxynaphthalenium ions are reported in 2 3-235) j ose of fluorinated anthracenium ions, among them the per-fluoroanthracenium ion, are available in... 

Spectroscopy in the ultraviolet and the visible region was one of the first physical methods applied to the studies of aromatic compounds in acid systems. By this method the first indications were obtained for arenium ions. In particular, V. Gold and F. Tye showed the solutions of anthracene and 1,1-diphenylethylene in concentrated sulphuric acid to have absorption maxima very close in position and intensity 422 and 431 nm, respectively). This similarity meant that the hydrocarbons are protonated to form, respectively, the 9-H-anthracenium ion and the di-phenylmethyl cation having similar 7t-electron systems ... 

Table 36. Absorption Spectra of Naphthalenium and Anthracenium Ions (25 °Q...

The cleavage of a-phenylindenes to form indenylic cations is also described Conversions of this type are used to generate anthracenium ions from 9-phenyl-9,10--dihydroanthracene and its derivatives (see Sect. II). 

An IR spectrum has been recorded for the tetrabromoaluminate (vdth an admixture of heptabromodialuminate) of a 10-H-anthracenium ion in the range of90-3100 cm Based on the results of deuteration at 9- and 10-positions and of comparison with the spectra of anthracene, 9- and 10-substituted anthracenes and of an acridi-nium cation, the authors have performed the assignment of the observed absorption bands of the anthracenium ion and of the anions AlBr and Al Brf. The stretching... 

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