Methane Cations

Varied Methane Cations. The methane molecular ion (methane radical cation, CH4+ ), the parent ion in mass spectrometry, and the methane dication (CH42+) are of great significance and have been studied both experimentally and theoretically.800 802 Recent advanced studies have shown that the methane radical cation, CH4+ has a fivecoordinate planar structure as suggested in early calculations by Olah and Klopman.800... 

The mass spectrum of methane ta relatively simple because few fraf mentations a re possible. As Figure 12.2a ahows, th4 base peak has miz 16. which corresponds to- the unbragmented methane cation radical, called the parent peak or the molecuJar ion mass spectrum also shows peaks at miz = 15 and 14, corresponding to cleavage of the molecular ion into CH, and CH2 fragments. 

In Table 8, a sample of results from previous hfs calculations using the PP functional are presented [2,30,47-49], along with some recent results. Of the many hydrocarbons investigated thus far we include results obtained for the C3 species C3H5 (allyl radical) [2], c-C3H[Pg.317]

Computed hyperfine data for the methane cation radical, obtained in vacuum (PP/IGLO-III optimized geometry) and at the partially optimized, noble gas embedded structures. Comparison made with previous CISD and experimental data. 

Figure 15. Relative energies (kcal/mol) of the two methane cation - noble gas cluster models depicted in Fig. 14, as functions of distance between the noble gas atoms and the nearest atom(s) in CHJ. In the calculations, both the VWN and PP functionals are employed, keeping the PP/IGLO-III optimized geometry of CHJ (Fig. 14a) fixed throughout.

An analj is of the interactions of ions with ligands leads to valuable information which is difficult to obtain otherwise. Important data for resolving the dynamical structure of the protonated methane cation CHs arises from the infra-red spectra of CH5 (H2)n [45,61]. The topology of shells is projected on the properties of bare ions. The process of the consecutive electron photodetachment from the central anion indicates the existence of the well developed shell structure of complexes. The theoretically predicted electronic affinities for O AXn clusters calculated for theoretical structures of complexes agree with the known measured values (Table 3) [62,63]. The ionization potential of CHa Arn clusters is little... 

The addition of these color-on-demand systems may have an impact on the sensitivity if it interferes the initiation mechanism. Particular reactive initiator radicals (In) can easily abstract a hydrogen from leuco-dyes (XV). This results in the formation of a less reactive triaryl methane radical XVI. Oxidation of this intermediate yields the stable deeply colored cationic structure XVII. Thus, the reactivity/sensitivity of the initiator system reduces requiring to find an agreement between plate sensitivity and color formed. XVI can easily oxidize resulting in formation of the intensively blue-colored triaryl methane cation XVII. 

The mechanism of these reactions presumably involves the initial formation of ferrocenylcarbinol, followed by ionization in the strongly acidic media to the relatively stable ferrocenylmethylcarbonium ion. The latter is assumed to be in equilibrium with a ferricinium ion radical, which will dimerize to the dication, or react with ferrocene to form a diferrocenyl-methane cation, equation (6-3). 

Figure 10 Portion of the structure diagram for the C4H7 system showing only stable structures. The three-fold symmetry accounts for the scrambling of the three methylene carbon atoms via interconversion of the cyclopropylcarbinyl 1 and cyclobutyl 2 cations. The planar homoallyl structure 3 is obtainable from the same transition state for conversion of 1 to 2. The central structure 4 is a relatively high-energy trimethylene methane cation intermediate, incorrectly assigned a structure corresponding to tricyclobutonium ion in a mechanistic model of the scrambling of the methylenic carbons...

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