Nitrophenyl group

The nitration of nitro- and dinitro-biphenyls has been examined by several workers. i - As would be expected, nitration of the nitro-biphenyls occurs in the phenyl ring. Like a phenyl group, a nitrophenyl group is 0 -directing, but like certain substituents of the type CH CHA ( 9.1.6) it is, except in the case of w-nitrophenyl, deactivating. Partial rate factors for the nitration at o °C of biphenyl and the nitro-biphenyls with solutions prepared from nitric acid and acetic anhydride are given below. The high o p-v2X o found for nitration of biphenyl... 

An E-Z discrimination between isomeric oxaziridines (27) was made by NMR data (69JCS(C)2650). The methyl groups of the isopropyl side chains in the compounds (27) are nonequivalent due to the neighboring carbon and nitrogen centres of asymmetry and possibly due to restricted rotation around the exocyclic C—N bond in the case of the Z isomer. The chemical shift of a methyl group in (Z)-(27) appears at extraordinarily high field, an effect probably due to the anisotropic effect of the p-nitrophenyl group in the isomer believed to be Z. 

Nitrophenyl groups covalently bonded to classy carbon and graphite surfaces have been detected and characterized by unenhanced Raman spectroscopy in combination with voltammetry and XPS [4.292]. Difference spectra from glassy carbon with and without nitrophenyl modification contained several Raman bands from the nitrophenyl group with a comparatively large signal-to-noise ratio (Fig. 4.58). Electrochemical modification of the adsorbed monolayer was observed spectrally, because this led to clear changes in the Raman spectrum. 

Completely stereospecific and regiospecific ring-opening reactions were observed with the just mentioned nucleophiles when the 3-aryl substituent is a phenyl or a p-nitrophenyl group (Scheme 20) [30]. 

New photochemical cleavage reactions of ortho-substituted C=C double bonds were reported by introducing a 2-nitrophenyl group to the double bond104. Photolysis of 1-(2-nitrophenyl)-l-alkenes 174 in methylene chloride solution without oxygen affords aryl... 

The role of the serine residue in hydrolysis was further examined using pseudo-substrates, e.g. p-nitrophenylacetate—substrates which were only very slowly utilized by the enzyme. The p-nitrophenyl group was slowly released and the acyl group became attached to the same serine in hydrolases which had been detected by DIPF (Kilby and Youatt, 1954). Mechanisms for peptide and ester hydrolysis were therefore proposed in which the acyl group became transiently and covalently bound to serines in catalytic sites (see Hartley et al. 1969). 

Comparison of the standard potentials of the radical anion of three a-nitrocumenes (o -nitrocumene, /7-cyano-a-nitrocumene and p-nitro-a-nitrocumene) revealed that the nitroallyl portion occurs in (90a) and (90b), while in (90c) the electron is added to the nitrophenyl group. It was concluded that homolytic cleavage takes place for the radical anions of (90a) and (90b) to give nitrite and the cumyl radical whereas the cleavage of radical anion (90c) is heterolytic. ... 

As shown in the previous sections, pyridine and related azaaromatic compounds possess a strong electron-withdrawing property equivalent to thep-nitrophenyl group and hence serve as good leaving groups. The facile... 

The chlorinated intermediate 255 is eliminated and cycloadds to Cjq, yielding pyrazo-linofullerenes of the structure 257 (Scheme 4.42). The 4-nitrophenyl-group can be replaced by a 4-methoxyphenyl- or a phenyl substituent. In this reaction various aromatics and substituted aromatics are tolerated as residues R (e.g. furan, ferrocene, pyrazole or benzene and substituted benzene). The nitro group of the nitrophenyl residue can be reduced with Sn-HCl to the aniline derivative, which can be further functionalized by amide coupling with acid chlorides [311]. 

Fig. 11. Molecular model of the conformation of a large segment of laurylimidazole polyethylenimine in aqueous solution, with some molecules of bound nitrophenylcaproate added. One of the bound molecules is pointed to by a white arrow the nitrophenyl group... 

X-Ray diffraction shows that the p- nitrophenyl group is equatorial and the morpholinocar-bonyl moiety axial in the isochroman-l-one cis-3,4-dihydro-4-morpholinocarbonyl-3-p-nitrophenyl-l//- 2-benzopyran-l-one (175) <78JCS(P1)1351). The pyranone ring has a distorted twist conformation. 

Nitrophenyl esters are often used as synthetic substrates for two reasons (1) the nitrophenolate ion is a very good leaving group so it forms a reactive substrate and (2) it has a characteristic absorption at 400 nm and is thus easily assayed spectrophotometrically. Both these factors are caused by the delocalization shown in equation 2.62. But, the use of the nitrophenyl group can give rise to misleading results on the requirements for catalysis since, as discussed later (equation 2.70), it is expelled without acid catalysis. 

The basic structural unit needed for activity is R-pdT-R. R may be a free 3 -OH but a phosphate here markedly increases substrate binding. R may be a p-nitrophenyl group. The bond that is broken is the P-0 of the 5 -C—O-P ester linkage (60). 

As 2-vinylfuran rapidly polymerizes even in a nitrogen atmosphere in the presence of a stabilizer, yields obtained for these Diels-Alder reactions were very low. In fact, when the more stable 5-(4-nitrophenyl)-2-vinylfuran lb reacted with DMAD, the yield of the aromatized cycloadduct, dimethyl 2-(4-nitrophenyl)benzofuran-4,5-dicarboxylate 4b, was 50%. The 4-nitrophenyl group not only deactivated the vinylfuran for oxidation and polymerization, but also deactivated the diene system toward cycloadditions, and the reaction was successful only when conducted in boiling xylene. The decrease in reactivity of the reactive diene may account for the relatively low yield of methyl 2-(4-nitrophenyl)benzo-furan-4-carboxylate 6b obtained in a similar reaction with MP (73-AJC1059). 

When azirenoimidazoles were first synthesized [88] their photochromic properties were discovered all the crystalline 6-(4-nitrophenyl)-substituted aziridines, colorless or yellowish, became deep blue upon sunlight irradiation the coloration disappeared in a few days in the dark. Photochromism was also observed for azirenoimidazole hydrochlorides. Their crystals became red upon irradiation. Photochromic properties were also found for azirenoimidazoles without a nitrophenyl group on the aziridine cycle but they were much less pronounced. 

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