Non-electrolyte effects upon rates of nitration in anhydrous sulphuric acid

Abstract

Rate constants are measured for the nitration of benzenesulphonic acid and the benzoic acidium ion in anhydrous sulphuric acid at 25° in the presence of several concentrations of the non-electrolytes 2,4,6-trinitrotoluene, sulphuryl chloride, and nitromethane. The second-order rate constant for the nitration of benzenesulphonic acid, previously shown to depend markedly upon the initial substrate concentration, is now found to depend upon the total concentration of non-electrolytes present in the solution. Thus the rate constant can be kept fixed with a series of different substrate concentrations by supplementing with an inert non-electrolyte to give the same overall concentration. The rate of nitration of the charged benzoic acidium species on the other hand is unaffected by non-electrolytes, though electrolytes have a similar effect to that reported for benzenesulphonic acid. With the latter substrate, NaB(HSO₄)₄ has a similar effect to NaHSO₄, thus demonstrating the absence of a specific HSO₄^– effect.