Nitro group activating effects

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-... 

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. 

The aza group activation effect in the oxidative amination of azines is less than that of the nitro group. As an illustration the reaction of 4-nitroquinoline and liquid ammonia in the presence of KMn04 produced 3-amino-4-nitroquinoline only in 86% yield [52]. Oxidative amination of 5-nitroquinoline gave 6-amino derivative in... 

Investigations of the solubilities of aromatic compounds in concentrated and aqueous sulphuric acids showed the activity coefficients of nitrocompounds to behave unusually when the nitro-compound was dissolved in acid much more dilute than required to effect protonation. This behaviour is thought to arise from changes in the hydrogenbonding of the nitro group with the solvent. 

Nucleophilic Displacement Reactions. The strong electron-withdrawing effect of a trifluoromethyl group activates ortho and para halogen toward nucleophilic attack. Such chlorine labiUty is utili2ed in the manufacture of crop control chemicals containing trifluoromethyl and nitro groups. 

From the standpoint of geometrical considerations, the major difference is in the far greater steric requirements of the nitro group. This could result in either primary or secondary steric effects. Nevertheless, primary steric effects do not seem to be necessarily distinguishable by direct kinetic comparison. A classic example is the puzzling similarity of the activation parameters of 2-chloropyrimidine and 2,6-dinitrochlorobenzene (reaction with piperidine in ethanol), which has been described by Chapman and Rees as fortuitous. However, that nitro groups do cause (retarding) primary steric effects has been neatly shown at peri positions in the reaction with alkoxides (see Section IV,C, l,c). 

As to the electron-withdrawing substituents, the activating effect of a nitro group in the piperidino-dechlorination of 2-chloropyridine involves factors of 7.3 x 10 and 4.6 x 10 from the para and ortho positions, respectively. An ortho-cyano group was found to be... 

Steric hindrance to activation by carboaromatic nitro groups is well-known, but there seems to be no analogy in the chemistry of azines. The lone-pair of azine-nitrogen has a steric effect comparable " to, somewhat greater than, or somewhat less " than a hydrogen atom. It is not certain whether bulky groups such as i-butyl produce a steric distortion of the lone-pair orbital and whether activation or deactivation results. 

The A-oxidation of 3-chloropyridazines increases their reactivity toward methoxide and sulfanilamide anions.The reactivity of 4-chloro- or 4-nitro-quinoline and of chloropyridines toward methoxide ion and piperidine is less than that of the corresponding A-oxides (see Tables II and XI, pp. 270 and 338). The activating effect of the A-oxide moiety in 3-halopyridine A-oxides is greater than that of a nitro group, and in fluoroquinoline A-oxides the activation is transmitted to resonance-activated positions in the adjoining rings. 

The relation of the activating effects of an azine-nitrogen and a nitro group depends on the compounds chosen for comparison and on the nucleophile. The ratio of the rates of reaction of 283 (Table III, line 2) and of 284 (Table VII, line 1) is... 

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