Nitro group, activation

Chapman and co-workershave shown that, in the reactions of nitro-2-chloropyridines with piperidine, aryl amines, or pyridine bases, a 5-nitro group activates more than a 3-nitro group (cf. Table VII, p. 276). 

Photoexcited aromatic compounds undergo substitution reactions with (non-excited) nucleophiles. The rules governing these reactions are characteristically different and often opposite to those prevailing in aromatic ground state chemistry 501a,b>, in contrast to the well known ortho/para activation in thermal aromatic substitutions, nitro groups activate the meta position in the photochemical substitution, as shown in (5.1) 502). 

A nitro group activates toward nucleophilic replacement of a halo atom412,541 or an amino group 152-497 in an adjacent ring position. 

When 2-bromo-4,5-difluoronitrobenzene is heated with sodium sulfide, a diaryl sulfide is formed. The nitro group activates halogens in ortho-and para positions for nucleophilic displacements. Which of the activated halogens is replaced in the reaction with sodium sulfide giving a diaryl sulfide, and what is the product ... 

Propose a mechanism for the conjugate addition of a nucleophile (Nuc ) to acrylonitrile (H2C = CHCN) and to nitroethylene. Use resonance forms to show how the cyano and nitro groups activate the double bond toward conjugate addition. 

On the other hand, the aromatic nitro group activates the ring towards nucleophilic addition. The addition may be followed by an elimination. This is exemplified by the preparation of 2,4-dinitrophenylhydrazine from 2,4-dinitrochlorobenzene. 

A A nitro group activates the ortho and para positions towards nucleophilic addition. The adduct from the 7-butyl hydroperoxide anion may then fragment with the loss of 7-butyl alcohol ... 

Ortho or para activated nitro aromatic compounds have been known to undergo nitro-displacement reaction to form various ortho and para substituted aromatic ethers [8]. In the above case, the powerful electron withdrawing effect of one nitro group activated the other nitro group although they are meta to eadi other. Other meta substituted bis(aminophenyl)arylene ethers reported are l,3-bis(3-amino-... 

The nitro group activates aliphatic systems and makes possible a number of addition reactions such as aldoiic addition of aldehydes (Henry reaction). Man-nich reaction, Michael addition, Diels - Alder reaction, for example (I55. ... 

Hey and Grieve [125] found in 1934 that the nitro group activates the aromatic ring towards homolytic substitution. For example, the competitive phenylation of toluene and nitrobenzene by phenyl radicals showed that the yield of nitrodiphenyls was about four times greater than the yield of methyldiphenyls. 

Nucleophilic substitution reactions The presence of nitro-groups activates the aromatic ring to nucleo-... 

Amination of aromatic nitro compounds often occurs smoothly and directly also on condensation with hydroxylamine in alkaline solution, the amino group normally entering ortho or para to the nitro group. One nitro group activates naphthalene derivatives sufficiently, but in the benzene series two are necessary to induce this reaction. 2-Nitro-l-naphthylamine was thus obtained (80%) from 2-nitronaphthalene,400 and 4-nitro-l-naphthyl-amine (60%) from 1-nitronaphthylamine.401 The amino group also enters the nitrated ring of quinoline derivatives. 

Even in RSU-1069 (Figure 1, 13), a nitroimidazole with an N-1 substituent terminating in an aziridine but insulated from the aromatic moiety by a 3-carbon chain, the inductive effect of the nitroimidazole group is sufficient that reduction of the nitro group activates the alkylating function. 

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