Kinetics, of nitration

The kinetics of nitration of anisole in solutions of nitric acid in acetic acid were complicated, for both autocatalysis and autoretardation could be observed under suitable conditions. However, it was concluded from these results that two mechanisms of nitration were operating, namely the general mechanism involving the nitronium ion and the reaction catalysed by nitrous acid. It was not possible to isolate these mechanisms completely, although by varying the conditions either could be made dominant. 

TABLE 4.4 The kinetics of nitration of nitrobenzene in various medial... 

The kinetics of nitration in acetic anhydride are complicated. In addition to the initial reaction between nitric acid and the solvent, subsequent reactions occur which lead ultimately to the formation of tetranitromethane furthermore, the observation that acetoxylation accompanies the nitration of the homologues of benzene adds to this complexity. 

The kinetics of nitration of benzene in solutions at c. 20 °C in carbon tetrachloride have been investigated. In the presence of an excess of benzene (c. 2-4 mol 1 ) the rate was kinetically of the first order in the concentration of benzoyl nitrate. The rate of reaction was depressed by the addition of benzoic anhydride, provided that some benzoic acid was present. This result suggested that benzoyl nitrate itself was not responsible for the nitration, but generated dinitrogen pentoxide... 

First-order nitrations. The kinetics of nitrations in solutions of acetyl nitrate in acetic anhydride were first investigated by Wibaut. He obtained evidence for a second-order rate law, but this was subsequently disproved. A more detailed study was made using benzene, toluene, chloro- and bromo-benzene. The rate of nitration of benzene was found to be of the first order in the concentration of aromatic and third order in the concentration of acetyl nitrate the latter conclusion disagrees with later work (see below). Nitration in solutions containing similar concentrations of acetyl nitrate in acetic acid was too slow to measure, but was accelerated slightly by the addition of more acetic anhydride. Similar solutions in carbon tetrachloride nitrated benzene too quickly, and the concentration of acetyl nitrate had to be reduced from 0-7 to o-i mol 1 to permit the observation of a rate similar to that which the more concentrated solution yields in acetic anhydride. 

The kinetics of nitration have been studied fairly intensively over a number of years and show that the reaction can be represented by the general steps... 

Extension of this work to the kinetics of nitration of N-methyl- and N, N-dimethylaniline48 gave the rate coefficients given in Table 7 together with those... 

The kinetics of nitration by nitric acid in nitromethane and acetic acid have been studied in detail40, and interpretation of the data here is perhaps made a little more difficult by the fact that spectroscopic and conductimetric analyses give no evidence for the existence of the nitronium ion in these media57. 

Similar conclusions have been reached by Champetier and Foex [70] and by Trombe, Foex and Champetier [71]. Wilson and Miles also studied the kinetics of nitration in nitric acid vapour. On the basis of these investigations they concluded that two molecules of nitric acid take part in the reaction with one OH group ... 

Data have been presented on the kinetics of nitration of acetanilide in mixtures of nitric and sulfuric acids.29 A review discusses the several mechanisms operative in the nitration of phenol including /> / -sclective nitrosation-oxidation and mechanisms involving phenoxy radical-nitrogen dioxide reaction yielding a 55 45 ortho para nitration ratio.30 The kinetics of mononitration of biphenyl-2-carboxylic acid have been investigated in several solvents. The maximum ortho para product ratio of 8.4 is observed in tetrachloromethane.31 Nitration products were not formed in the presence of dioxane.31,32 Quantum-chemical AMI calculations were performed and the predominant formation of the ortho-nitro product is accounted for by stabilization of the cr-complex by the carboxyl group.33... 

Reduction Kinetics of Nitrate and Nitrite with an Fe° System... 

The kinetics of nitration in sulphuric acid of both pyrazole and imidazole have been studied.87 Data have already been quoted (tables 8.1, 8.3) to support the view that the nitration of both of these compounds at Q4)... 

Alowitz MJ, Scherer MM. Kinetics of nitrate, nitrite, and Cr(VI) reduction by iron metal. Environ Sci Technol 2002 36 299-306. 

Ingold, Hughes and Reed [39] studied the kinetics of nitration of aromatic compounds with nitric acid only and found that it was a first order reaction. Its rate, VN/ may be expressed by an approximate equation ... 

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