Nitronium salts bond reactivity

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. 

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