Alkanes nitrolysis

Table 5.31. Nitration and Nitrolysis of Alkanes and Cycloalkanes with N02+PF6 476...

The hydrogen peroxonium ion may be considered as an incipient OH+ ion capable of electrophilic hydroxylation of single (effect reactions similar to such previously described electrophilic reactions as protolysis, alkylation, chlorination (chlorolysis), and nitration (nitrolysis). 

Tertiary C-H tonds show the highest reactivity. C-C bonds are generally more reactive than secondary or primary C-H bonds, leading to preferential nitrolysis of n-alkanes(cleavage nitratlcn) The nitronium ion, which is linear itself, does not seem to exercise excessive steric hindrance in the transition states of the reactions, where it is substantially bent (indicated also from its behavior in electrophilic aromatic substitutions). Side products of the nitrolysis are methyl, ethyl, and isopropyl fluoride (formed by the reaction of PFg with the cleaved alkylcarbenium ions) or secondary alkylation products, themselves capable of undergoing reaction with the nitronium salt. 

HF and HSO3F (or other superacid) solutions (see subsequent discussion). Higher alkanes and isoalkanes gave yields of 5-10% and adamantane was nitrated in 30% yield. Data indicate that nitratioa (nitrolysis) of alkanes with nitronium salts proceeds in accordance with the generalized concept of electrophilic reactions of single bonds [77] involving two-electron, three-center bond carbocationic intermediates (transition states) as illustrated with case of the nitration of methane. 

Compared to tertiary C—H bonds, C—C bonds are less reactive primary and secondary C—H bonds have even lower reactivity. Cleavage nitration (nitrolysis of C—C bonds) of -alkanes is the predominant reaction. 

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