Ions, nature

Arnold F and Henschen G 1978 First mass analysis of stratospheric negative ions Nature 257 521-2 Eisele F L 1989 Natural and anthropogenic negative ions in the troposphere J. Geophys. Res. 94 2183-96 Oka T 1997 Water on the sun—molecules everywhere Science 277 328-9... 

Acyl cations are relatively weak electrophiles. This is easily understood, because their structure is of a predominantly linear carboxon-ium ion nature, with the neighboring oxygen atom delocalizing charge and limiting their carbocationic nature. 

The results of aetivatioii of aeyl cations led to our study of other carboxonium ions. Carboxonium ions are highly stabilized compared to alkyl cations. As their name indicates, they have both carbocationic and oxonium ion nature. 

A notable exception is the noble gases, which do not form ions naturally.)... 

This differs from the normal structure (1) in that an electron in the Cu+ ion has been transferred from the 3d shell to the 4s shell. In such a state of excitation, the Cu+ ion naturally retains its charge unchanged but acquires a free valence. 

Heitmann, H and F. Arnold, Composition Measurements of Tropospheric Ions, Nature, 306, 747-751 (1983). 

Arnold, F., and G. Henschen, First mass analysis of stratospheric negative ions, Nature, 275, 521-522,... 

Cram s original studies287 established, based on kinetic and stereochemical evidence, the bridged ion nature of (3-phenylethyl cations in solvolytic systems. Spectroscopic studies (particularly1H and 13C NMR)288-291 of a series of stable long-lived ions proved the symmetrically bridged structure and at the same time showed that these ions do not contain a pentacoordinate carbocation center (thus are not nonclassical ions ). They are spiro[2.5]octadienyl cations 111 (spirocyclopropylbenzenium ions)—in... 

The effect of the introduction of two electron-deficient centers into the bicyclo [2.2.1]heptyl skeleton (norbornyl framework) has been explored.406 A 13C NMR spectroscopic study of several substituted 2,5-diaryl-2,5-norbornadiyl dications 193 reveals the regular dicarbenium ion nature of the system. 

Results of protoly tic reactions of hydrocarbons in superacid media were interpreted by Olah as indication for the general electrophilic reactivity of covalent C H and C—C single bonds of alkanes and cycloalkanes. The reactivity is due to the tr-donor ability of a shared electron pair (of cr-bond) via two-electron, three-center bond formation. Consequently, the transition state of the reaction, is of three-center bound pentacoordinate carbonium ion nature [Eq. (5.5)]. 

Shechter, Y. and S.J.D. Karlish. 1980. Insulin-like stimulation of glucose oxidation in rat adipocytes by vanadyl (TV) ions. Nature 284 556-8. 

Olah et al. (1979a) reinvestigated ion [241] prepared from [240 R = OH] to confirm its proposed free carbonium ion nature and obtained essentially the same results. It is interesting to note that the C-chemical shift sum of ion [241] actually is 48 ppm less than the corresponding hydrocarbon [240] (R = H) confirming its nonclassical structure according to the criterion of Schleyer et al. (1980). 

Table 2 Main families of luminescent ions, nature of transitions, and order of magnitude of radiative lifetimes (values at 300 K, except for the charge transfer (CT) emission of Ce + and Yb + whose emission is affected by thermal quenching at room temperature)...

Arijs E., Nevejans D and Ingels J., Unambiguous mass determination of major stratospheric positive ions. Nature 288, 684 (1980). 

Quednau BD, Nicoll DA, Philipson KD. The sodium/calcium exchanger family-SLC8. Pflugers. Arch. 2004 447 543-548. MacLennan DH, Green NM. Structural biology. Pumping ions. Nature 2000 405 633-634. 

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