Nitro group influence

In some situations the nitro group behaves as if it exerted its influence mainly by the inductive process, but in nitration its behaviour seems to place it with this group of —I —M substituents. The precise way in which a sulphone group is described depends on how much weight is given to the ability of the sulphur atom to expand its octet the positive... 

The stabilizing influence in the hydrated cation is the amidinium resonance. If a solution of the cation is neutralized, a short-lived hydrated neutral molecule (4) (half-life 9 sec at pH 10) is obtained with an ultraviolet spectrum similar to that of the hydrated cation but shifted to longer wavelengths (5 m/ ). Supporting evidence can be derived from the anhydrous nature of the cation of 4-nitroiso-quinoline (pK 1.35), in which the nitro group has a similar electronic influence to that of the ring nitrogen atom N-I in quinazoline and where amidinium resonance is not possible. 

F. Terrier, Nucleophilic Aromatic Displacement The Influence of the Nitro Group", VCH Publishers, New York (1991). 

Adsorbability is influenced strongly hysteric hindrance, and because of this almost any function can be reduced in the presence of almost any other function in suitably constructed molecules. A case in point is the reduction of the aromatic ring in I in preference to reduction of the nitro function, producing 2. However, when R = CH3 (3) the nitro group was reduced instead, a fact attributed to a less sterically crowded environment 109). 

Nitration differs from halogenation since here the strongly electron-withdrawing effects of the nitro substituents first introduced influence the reactivity and the positions of further introduced substituents. Therefore, it is possible to prepare under carefully controlled reaction conditions different substitution products.100 103 The preparation of the tetrasubstituted product cannot be achieved since the deactivating effects of three nitro groups are too strong.104... 

A group with a more powerful (electron-withdrawing) inductive effect, e.g. NOa, is found to have rather more influence. Electron-withdrawal is intensified when the nitro group is in the o- or p-position, for the interaction of the unshared pair of the amino nitrogen with the delocalised it orbital system of the benzene nucleus is then enhanced. The neutral molecule is thus stabilised even further with respect to the cation, resulting in further weakening as a base. Thus the nitro-anilines are found to have related p a values ... 

In 1994 we published the first chiral dendrimers built from chiral cores and achiral branches [ 1,89], see for instance dendrimer 57 with a core from hydroxy-butanoic acid and diphenyl-acetaldehyde and with twelve nitro-groups at the periphery (Fig. 21). As had already been observed with starburst dendrimers, compound 57 formed stable clathrates with many polar solvent molecules, and it could actually only be isolated and characterized as a complex [2 (57- EtO-Ac (8 H20))]. Because no enantioselective guest-host complex formation could be found, and since compounds of type 57 were poorly soluble, and could thus not be easily handled, we have moved on and developed other systems to investigate how the chirality of the core might be influencing the structure of achiral dendritic elongation units. 

Extensive structure-activity relationships for NO release from oximes do not currently exist. Structural changes do influence the rate of NO release from the nitro-containing oximes, such as FK409 (9, ti/2 = 46 min, Fig. 7.2) [46, 59]. Changing the alkyl group attached to the carbon of the nitro group can increase (12, -CH2OCH3, ti/2 = 2.6 min, Fig. 7.2) or decrease (13, -tertBu, ti/2 = 2900 min, Fig. 7.2) the rate of NO release from... 

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