Direct Nitration of Alkanes

[pHarmacist]

Electrophilic nitration of alkanes with nitronium hexafluorophosphate
George A. Olah,* Pichika Ramaiah, and G. K. Surya Prakash

Proc. Natl. Acad. Sci. USA. 1997 October 28; 94 (22): 11783–11785

(http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=23573)

Nitration of alkanes such as methane, ethane, propane, n-butane, isobutane, neopentane, and cyclohexane was carried out with nitronium hexafluorophosphate in methylene chloride or nitroethane solution. Nitration of methane, albeit in poor yield, required protolytic activation of the nitronium ion. The results indicate direct electrophilic insertion of NO2 + into CH and CC ó-bonds.

[Rhodium]

nitronium hexafluorophosphate

Ouch - how is this made? It sounds like an awfully expensive reagent - nitronium tetrafluoroborate is €150/25g in the Aldrich catalog and the hexafluorophosphate isn't even listed...

I think gas-phase nitration with HNO₃ wins over this method for all purposes except to write a fancy publication.

[Antoncho]

Ouch - how is this made?

Not that i'm interested in it, but, - since you asked...

It's made by adding PF₅ to the mixture of anh. HNO3/HF and filtering the pptated salt  Sounds like fun, doesn't it?

HF can bee formed in situ from the same pentafluoride, yield in this case sucks, though - see

Patent US3092459

Other perfluoro Lewis acids may bee used as well, see

Patent US3403987

Antoncho