Nitro group, effect behavior

Nitro groups in the homocyclic ring of 1,2-benzisoxazoles have been reduced to the corresponding amino groups without opening of the isoxazole nucleus. SnCU/HCl and Adam s catalyst/H2 have both proved effective in this respect. Similar behavior was observed for nitro groups in the isomeric 2,1-benzisoxazoles (67AHC(8)277,pp.295,33l). 

The behavior of aminopyrazole 88 (R = 4-NO2—C6H4) under these conditions was quite different diazotization using nitrous acid in concentrated hydrochloric acid afforded an alkynylpyrazole diazonium chloride, which did not participate in the Richter reaction, probably due to the electron-withdrawing effect of the nitro group. Instead, after neutralization of the hydrochloric acid with sodium hydrogen... 

A similar behavior in a different reaction (Table XVII) shows that when the coplanarity of a N02 group is prevented in an SNAr reaction, the activating power of the nitro group, due in part to its resonance accepting effect (less than that of a ring nitrogen (54JCS1190). 

Moreover, the contribution of the o-nitro group on the spectral behavior was confirmed to be clearly effective in solution by comparison with amine complexes of p-nitrophenylazophenol crown 40 (kmax ca. 40-50 nm in EtOH). Figure 11... 

Considerable effort has been devoted to the determination of rate and equilibrium constants for benzene derivatives with meta- and pnrn-trifluoro-methyl substituents in a search for an exalted substituent effect which would provide evidence for special electron delocalization. Resonance interactions are generally detectable by such procedures. To illustrate, two sigma constants Op-NOi p-N(h with values of 0.78 and 1.24, respectively are necessary to describe the behavior of the nitro group quantitatively by the Hammett equation... 

Talik studied the behavior of 3-chloro-4-nitropyridine-l-oxide with various reagents, and showed that sodium methoxide causes replacement of the nitro group, while amines, on the other hand, effect displacement of the halogen. 

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