Nitric acid equilibrium in concentrated trifluoromethanesulfonic acid studied by Raman spectroscopy
Abstract
Mixtures of CF3SO3H–H2O–HNO3 have been analysed by Raman spectroscopy and the ionic species formed in the protonation–dehydration equilibrium of nitric acid (HNO3+ CF3SO3H ⇌ NO2++ CF3SO3–+ H2O) have been estimated. In the range 80–90 wt% CF3SO3H the titration curve of NO2+ has been determined.
In the range 90–100 wt% CF3SO3H, linear relationships have been found, at a given acidity, in the plots of [NO2+]versus[CF3SO3–] using different concentrations of nitric acid. Decreasing slopes are observed with increasing acidity of the medium. The involvement of NO2+·CF3SO3– ion-pairs in the range above 90 wt% CF3SO3H is suggested, and the influence of these species on nitration rates is discussed