Zerz-Butyl cation

I.6. Higher Alkonium Ions The acid-induced H-D exchange of isobutane (49) in deuterosulfuric acid was studied by Otvos and coworkers. All nine methyl hydrogens were readily exchanged, but not the methine hydrogen. The mechanism for this observation is considered to involve the initial formation of trivalent zerz-butyl cation (50), probably in an oxidative... 

Lewis superacid-catalyzed direct alkylation of alkanes is also possible with alkyl cations prepared from alkyl halides and SbFs in sulfuryl chloride fluoride solution. " Typical alkylation reactions are those of propane and butanes by 2-butyl and ZerZ-butyl cations. The ClfU-Sbfs and C2H5F-SbF5 complexes acting as incipient methyl and ethyl cations besides alkylation preferentially cause hydride transfer. Since intermolecular hydride transfer between different carbocations and alkanes are faster than alkylation, a complex mixture of alkylated products is usually formed. A significant amount of 2,3-dimethylbutane was, however, detected when propane was propylated with the 2-propyl cation at low temperature [Eq. (6.36)]. No 2,2-dimethylbutane, the main product of conventional acid-catalyzed alkylation, was detected, which is a clear indication of predominantly nonisomerizing reaction conditions. 

Discuss the optimum number of electrons (two, four, or six). Why is it desirable that A is the less electronegative element or group Do BF3 and ZerZ-butyl cation fit the pattern Hint The compound has threefold symmetry and some MOs will be degenerate. 

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