Second order reactions nitric acid from

Kinetic studies with benzene in acetic anhydride containing 0.4-2 M nitric acid at 25 °C show the reaction to be first-order in benzene and approximately second-order in nitric acid this falls to first-order in nitric acid on addition of sulphuric acid, which also increases the first-order rate coefficient (first-order in benzene) from 4.5 x 10-4 to 6.1 x 10 4. By contrast the addition of as little as 0.001 M sodium nitrate reduced the rate to 0.9 x 10-4 without affecting the kinetic order70. These results were, therefore, interpreted as nitration by nitronium ion via equilibria (21a) and (22). 

A kinetic study of nitrous acid-catalyzed nitration of naphthalene with an excess of nitric acid in aqueous mixture of sulfuric and acetic acids (Leis et al. 1988) shows a transition from first-order to second-order kinetics with respect to naphthalene. (At this acidity, the rate of reaction through the nitronium ion is too slow to be significant the amount of nitrous acid is sufficient to make one-electron oxidation of naphthalene as the main reaction path.) The reaction that initially had the first-order in respect to naphthalene becomes the second-order reaction. The electron transfer from naphthalene to NO+ has an equilibrium (reversible) character. In excess of the substrate, the equilibrium shifts to the right. A cause of the shift is the stabilization of cation-radical by uncharged naphthalene. The stabilized cation-radical dimer (NaphH)2 is just involved in nitration ... 

These are the most common diazeniumdiolates, formed by the reaction of secondary amines and polyamines with nitric oxide in basic media [214, 215]. They are stable solids, capable of regenerating two equivalents of nitric oxide along with the starting amine in neutral or acidic buffers. The half-life of NO generation varies from a few seconds to many hours, depending on the amine. The decomposition to NO is a spontaneous, first-order reaction at constant pH. 

Dinitrobenzene was prepared from mononitrobenzene by addition of three equivalents of nitric acid. After 20 minutes the mono was half used up and the o-, m- and p- forms of the dinitrobenzene were present in the proportions 6.4, 93.5 and 0.1. Find the second order specific rates of the three reactions. 

The concentration x, of the nitrated product formed after time t is obtained from Eq. (3.5). Pseudo-first-order rate coefficients are found from Eq. (3.6) [by plotting log (D - Df) against /] and second-order rate coefficients are calculated from Eq. (3.7), where b is the concentration of nitric acid, a is the initial concentration of the substrate, and D0, D, and D, are, respectively, the optical densities initially, after time t, and after complete reaction. (In some cases there is no initial absorption at Xmax so D0 is zero.) Second-order rate coefficients, which are obtained from the... 

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