Thermodynamic nitration rates of aromatic compounds. Part 3. Nitration of aromatic compounds in concentrated aqueous trifluoromethanesulphonic acid
- 1 January 1991
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 3,p. 423-429
- https://doi.org/10.1039/p29910000423
Abstract
The kinetics of nitration of mesitylene, toluene, benzene, bromobenzene and methyl phenyl sulphone, reacting as free bases in the range 50–100 wt% CF3SO3H are reported. The rates, related both to the stoichiometric concentration of nitric acid (rate =k2obs [Ar][HNO3]) and to the effective concentration of electrophilic species (rate =k2°[Ar][NO2 +]) have been determined. Compared with k2obs , which exhibits a large solvent effect, the true nitration rates (k2°) were found to be almost independent of medium acidity and, for a given compound, rather similar in different acids. The k2° values were also found to be linearly related to the rate constants for nitration in the gas phase. The rates of reaction for methyl phenyl sulphone in 80–100 wt% acid were found to be lower in CF3SO3H than in H2SO4 by a factor of 8. A similar rate profile is observed, however, with an increase up to 90% acid and a decrease between 90 and 100%. The dependence of the rate profiles upon acidity and temperature in very concentrated acid solutions is discussed.Keywords
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