Nitronium salts hydrocarbons

The nitration of aliphatic hydrocarbons with dinitrogen pentoxide and nitronium salts has been described. Topchiev gives an extensive discussion of works related to hydrocarbon nitration conducted prior to 1956. 

Nelson KL, Brown HC (1955) Nitronium salts in organic chemistry. In Brooks BT, Kurtz SS, Boord E, Schmerling L (eds) The chemistry of petroleum hydrocarbons. Reinhold Publ Corp, New York... 

Hydrocarbons are efficiently nitrated by nitronium salts under anhydrous conditions as shown by Ingold el al. and subsequently developed by Olah et al. (54] as a general preparative nitration method... 

Mixture of nitric and sulfuric acid (mixed acid) used extensively in nitration of aromatic hydrocarbons, is generally unsuitable for nitration of alkanes, since primary nitroalkanes are rapidly hydrolyzed by hot sulfuric acid and secondary and tertiary nitroalkanes form tars (in all probability via rapid alkene-forming elimination and subsequent polycondensation, polymerization, etc.). It is, however, significant to point out that it is not necessarily the lack of reactivity of paraffins with mixed acid that makes the nitration of saturated hydrocarbons unsuitable, but that fast secondary reactions of any nitro products formed (as well as oxidative side reactions) can take place. This difficulty can be, at least in part, overcome by using preformed nitronium salts as nitrating agents. 

The finding that highly deactivated aromatics do not react with N02 salts is in accord with the finding that their greatly diminished TT-donor ability no longer snffices to polarize NOi. Similarly, (j-donor hydrocarbons such as methane (CH4) are not able to affect such polarization. Instead, the linear nitronium ion is activated by the superacid. Despite the fact that is a small, triatomic cation, the 11011-... 

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