Mononitrated benzene derivative

Conversion to the mononitrated benzene derivative increased linearly with increasing flow velocity because of enhanced mass transfer. The formation of phenol by-products increased in the same manner for similar reasons. In turn, consecutive by-products, dinitrated aromatics, were formed in a linear decreasing fashion. This was explained by a mass-transfer-induced removal of the mononitrated product from the reacting slug. 

TABLE 5. Isomer ratio (%) in the mononitration of benzene derivatives and C6o fullerene solubility in these derivatives [34]... 

It is impossible to introduce more than three nitro groups into one benzene ring the products would contain at least two nitro groups in the ortho-position to one another, and such compounds are very reactive. The two isomeric tetranitrobenzenes should be preparable by oxidation of other nitrogenous groups present in trinitrobenzene derivatives.169 In di- and tri-nitrations the nitro groups normally enter positions meta to one another, in accord with the well-known rules of substitution. However, occasionally, when these rules are overcome by some specific activation by other substituents, 0-dinitro compounds will result for instance, about 4% of m-nitrotoluene is formed on mononitration of toluene and on further nitration this leads to a mixture of 2,3-, 3,4-, and 3,6-dinitrotoluenes. 

The reaction was found particularly useful as a relatively selective and mild nitration method, for example allowing mononitration of durene and other highly alkylated benzenes, which with mixed acid usually undergo dinitration. (Table XIl). Methyl nitrate-boron trifluoride can also be used to achieve dinitration of tet-ramethylbenzenes by using two and three molar excess of methyl nitrate, respectively. Relative yields of mono- and dinitro product compositions are shown in Table XIII. Other Friedel-Crafts type catalysts can also be used, but boron trifluoride was found to be the most suitable. Aluminum trichloride and titanium (IV) chloride in the nitration of pentamethylbenzene caused formation of significant amounts of chlorinated derivatives, whereas sulfuric acid led to nitrodemethylation products. 

Mononitration of 1-hydroxynaphthalene could be obtained by use of ammonium hexanitra-tocerate(IV) supported on silica gel in acetonitrile (Chawla and Mittal, 1985) (scheme 39). The same reaction with CAN in acetic acid give the 2,4- and 4,6-dinitro derivatives. By the same method, 2-hydroxy naphthalene is converted into l-nitro-2-hydroxy naphthalene and 4-nitro-2-hydroxynaphthalene (scheme 40). The 1-alkoxynaphthalenes can be mononitrated regioselectively in the 4-position (scheme 41). The lower reactivity of CAN supported on silica gel is also evident from the fact that naphthalene derivatives are not oxidized into 1,4-naphthoquinones. The authors noticed that no reaction could be observed when ammonium hexanitratocerate(IV) was replaced by a mixture of ammonium nitrate and ammonium cerium(IV) nitrate. Silica supported CAN has also been used for the nitration of methoxyben-zenes (Grenier et al., 1999) and less electron rich aromatic compounds like benzene, toluene, chlorobenzene and bromobenzene (Mellor et al., 2000) (scheme 42). For the less electron rich aromatics, dichloromethane is used as solvent instead of acetonitrile. In most cases, the yields are good to excellent. 

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