Oxygen cation

The acid catalyzed rearrangements of peroxides, in which the migrating groups show the same migration aptitudes as in carbonium ion rearrangements, may be represented as rearrangements of oxygen cations.89-91... 

In the presence of ferrous salts the hydroperoxide decomposition goes by way of an oxygen monoradical intermediate, with different migration aptitudes. Para nitrophenyl rather than phenyl migrates under the radical conditions. Although the oxygen cation resembles the carbonium ion both chemically and in charge type, it may also be a diradical ... 

The decomposition of the peroxide IX, which gives acetophenone when the conditions are such as to favor the radical mechanism, gives methyl ethyl ketone if the reaction is run in acid. This is because of the superior migration aptitude of phenyl groups in real or incipient oxygen cations.112... 

Organic peroxides can decompose either homolytically into a pair of oxygen radicals or heterolytically to give an oxygen cation and... 

Again the mechanism as written is not meant to imply a completely free oxygen cation as the intermediate. A concerted ionization and rearrangement seems more likely. 

Another reaction in which an oxygen cation is plausible as an intermediate is in the ozonization of olefins. Ozonides are now known to have many structures, but the molozonide precursor of the classical" or most common ozonide is believed to have a four-membered, cyclic structure. Criegee and the author have independently proposed a mechanism in which heterolytic fission of the cyclic peroxide bond leads to an intermediate that can rearrange either to the classical ozonide or to an "abnormal ozonide 816 328... 

Cerda, B.A. Horn, D.M. Breuker, K. Carpenter, B.K. McLafferty, F.W. Electron Capture Dissociation of Multiply-Charged Oxygenated Cations. A Nonergodic Process. Eur. Mass Spectrom. 1999, 5,335-338. 

Figure 18. Correlation of carbon-13 chemical shifts with charge for some oxygenated cations. Copied from Olah and White (1968), with permission.

The protonation of esters in superacid solvents (HSO3F—SbFs and HF—BF3) also occurs on the carbonyl oxygen (cation [202])... 

Silicates - Si02, or compounds of various cations with various complex ions of silicon and oxygen. Cations can combine with individual Si044- tetrahedra, chains of Si032, and sheets of Si40104. Silicates are the most abundant minerals in chondrites, IDPs, and most types of differentiated materials. 

Termination of trivial names of many oxygenated cations uranyl... 

The goal of the present review is to demonstrate the wide potential for using newly developed methods to synthesize 2-benzopyrylium salts and to discuss in detail the numerous and unusual transformations of this class of oxygen cations in comparison with monocyclic pyrylium salts, i.e., the study of influence of benzo[c]annelation. 

Besides the anionic oxygen, cations are located at certain sites, and most of these sites are hidden or inaccessible to the adsorbate molecules. However, with molecules with permanent dipoles and quadruples, the interactions with these few exposed cations can dominate the total interaction potential. 

Aerobic oxidative cyclization of 2,2-dihydroxystilbenes via oxygen cation radical leading to the formation of c -4b,9b-dihydrobenzofuro[3,2-h]benzofurans was carried out in an enantioselective manner by using (nitrosyl)Ru(salen) as a catalyst under irradiation conditions <02CL36>. 

The solid solution (ss) on the left has been represented as a mixture consisting of 1 — X moles of magnetite and x moles of zinc ferrite per formula unit of ss. It is assumed that the zinc ferrite moiety remains passive while any changes relating to the oxygen/cation composition occur exclusively in the magnetite component. 

---