Nitration by acyl nitrates in organic solvents

Ingold et al. showed that rates of nitration by benzoyl nitrate in carbon tetrachloride were depressed by the addition of benzoic anhydride. Thus addition of 0.035 M of the anhydride to a solution 2.36 M in benzene and 0.030 M in nitrate decreased the first-order rate coefficient from 44x 10-4 to 20xl0-4. This is consistent with nitration by dinitrogen pentoxide formed via equilibrium (37), viz. 

The equilibrium is apparently acid catalysed, for the pure anhydride had no effect unless benzoic acid was present. 

Further evidence for this mechanism comes from the fact that a solution 0.305 M in dinitrogen pentoxide and 0.0346 M in anhydride, i.e. equivalent to the conditions above, gave almost the same rate, much slower than that obtained in the absence of the anhydride addition of further amounts of anhydride produced a regular decrease in the rate. 

No satisfactory analysis has been made with acetyl nitrate but the qualitative retarding effect of addition of acetic anhydride100 has been likewise interpreted as resulting from the preformation of dinitrogen pentoxide. 

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