Reactivity, of nitro group

The reactivity of nitro groups positioned olp- to other nitro groups has implications for the use of other polynitroarylenes as explosives. For example, of the numerous possible isomers of trinitrotoluene, only the symmetrical 2,4,6-isomer (a-TNT) is chemically stable enough for use as an explosive. Only in the case of the 2,4,6-isomer are the three nitro groups positioned m- to one another all other isomers of trinitrotoluene contain either one or two nitro group in... 

The reactivity of nitro groups was considered in CHEC-I <84CHEC-l(3B)i>, largely from the aspect of reduction, which is readily accomplished by a range of methods. Reduction can be selective in the presence of A -oxides, though condensation products are sometimes produced. 

Much of the reactivity shown by the ring atoms and substituents of pyrimidine is akin to that of the corresponding parts of 1,3-dinitrobenzene and 3-nitropyridine. This arises from the quantitatively similar electron-withdrawing effects of doubly-bound ring nitrogen atoms and of nitro groups in reducing sharply the aromaticity of the cyclic system. 

Secondary steric effects of nitro groups are more easily detected by comparing the reactivities with those of aza derivatives. For example, in structure 20 the rate depression on passing from methyl to -butyl is only 2.5-fold and can be attributed to an inductive effect, whereas in structure 21 a similar change involves the factor 16, which can be attributed in part to steric inhibition of resonance (S.I.R.) of thep-N02 group (reaction with piperidine). 

Since various substituents are tolerated, the Friedlander reaction is of preparative value for the synthesis of a large variety of quinoline derivatives. The benzene ring may bear for example alkyl, alkoxy, nitro or halogen substituents. Substituents R, R and R" also are variable. The reaction can be carried out with various carbonyl compounds, that contain an enolizable a-methylene group. The reactivity of that group is an important factor for a successful reaction. 

A review of such derivatives appeared in 2000,1273 it is especially useful for the electronic effects of nitro groups on the reactivities of other substituents in the molecule. Mass spectra have also been reviewed.492... 

INFLUENCE OF NITRO GROUPS ON REACTIVITY OF HYDROGEN ATOMS AND SUBSTITUENTS. NUCLEOPHILIC REACTIONS... 

The increased reactivity of the whole molecule or single groups, which is often associated with the entrance of nitro-groups, is also apparent in the capability of some nitro-bodies to be relatively easily oxidized. The little that is known is appended to the description of the behavior of the individual members. The characteristic features of the oxidation processes in question have been explained in the first chapter (p. 27 et seq.). 

The introduction of nitro groups at the upper rim of calix[4]arenes is a quick and useful method for the preparation of functionalized calix[4]arenes. This reaction is quite general and can be conveniently carried out on a wide variety of calix[4]arenes substituted at the lower rim. When the starting calix-arene is partially substituted at the lower rim, the substitution takes place at the more reactive phenol rings. 

The reactive sensitiveness of nitro-groups toward alkalies increases with the increase of the nitro-groups in the molecule. 

Interest in an old reducing agent, sodium sulfide, was renewed when it was discovered that its reactivity toward nitro groups was sensitive to water. In the absence of water, the aromatic nitro group in (28) can be reduced selectively to (29), without reduction of the aliphatic nitro group, but compounds such as (30), which contain a tertiary aliphatic nitro group eliminate the nitro moiety to yield styrene derivatives (31 Scheme 5). A unique application of the sulfide reduction involves the preparation of isomerically pure substituted aromatic nitro compounds and anilines. ... 

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