Bismuth in Organic Synthesis Green Chemistry

The second of the three reaction steps above (5B.88) can then be viewed as a nucleophilic displacement where a C-H bond of methane acts as the nucleophile to kick H2 out of CH5+  

The C2H7 cation so produced is expected to be capable of eliminating H2 to generate the ethyl cation, as shown below  

Note that we have never invoked the exceedingly unstable methyl cation (CH3+), which is known only to occur in the gas phase. Once the ethyl cation is produced, it can react with additional methane to ultimately produce the relatively stable t-butyl cation. 

Far stronger than magic acid is fluoroantimonic acid, which is a mixture of HF and SbF5 in various ratios. The 1 1 mixture is the strongest superacid known, some 2 x 10 (20 quin-tillion) times stronger than 100% sulfuric acid. Its molecular structure maybe represented as follows  

The F-H bond in HSbFg is clearly exceedingly weak, and the proton as a result is as close to naked as is possible in the liquid phase. As might be expected, fluoroantimonic acid is exceedingly corrosive and moisture-sensitive it can, however, be kept in Teflon containers. Compatible solvents include SO2CIF, SO2, and chlorofluorocarbons. 

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