Aniline, and substituted anilines

A convenient method for preparing pure AW-dialkyl anilines and substituted anilines directly from the corresponding amines consists in heating the latter with trialkyl orthophosphates ... 

The literature on the hydrogenation of aniline and substituted anilines suggests that the amine functionality can act as a poison [3, 4, 12 and 13] especially over platinum catalysts. The more basic the nitrogen the more... 

Even if the C104 ion is commonly believed to experience a scarce tendency to act as a ligand, nonetheless coordination of perchlorate as a monodentate ligand through an oxygen atom has been proposed in a number of nickel complexes containing alkylamines,1676 pyridine and substituted pyridines,1677-1680 arylamines such as aniline and substituted anilines,1681 phosphine and arsine oxides1682,1683 (Table 84). 

P.S. Kumbhar and G.D. Yadav Catalysts by Sulfur promoted super-acidic zirconia, condensation reactions of hydroquinone with aniline and substituted anilines, Chem.Engg.Sci. 44 (1989) 2535-2643. 

Aniline and Substituted Anilines. Methyl, chloro, nitro, methoxyl, ethoxyl, phe-noxyl, hydroxyl, carboxyl, carbalkoxyl, carbonamide, and sulfonic acid groups are primarily used as substituents. 

Aromatic azo compounds can be obtained by the oxidation of primary arylamines. The reagent most widely used for this purpose is activated manganese dioxide. This converts aniline and substituted anilines into the corresponding azo compounds in moderate to good yield. At room temperature the products are the n -azobenzenes, which are isomerized to the trans compounds on heating. It is probable that hydrazobenzenes are intermediates in the reaction, but these are more easily oxidized dim the starting anilines (Scheme 7). These oxidations are inhibited by electron-withdrawing substituents and some nitro-substituted anilines fail to react. 

Another interesting example is the aniline catalyzed formation of benzaldehyde semicarbazone [266]. Aniline and substituted anilines strongly accelerate the reaction of benzaldehyde with semicarbazide. The reaction rate and its pH dependence is equal to that of the formation of Schiff base from benzaldehyde and aniline (acid catalysis with changing rate-determining step) and does not depend on the concentration of semicarbazide. The final product is benzaldehyde semicarbazone, however. Obviously, benzaldehyde first reacts with aniline to form the Schiff base intermediate which then reacts rapidly with semicarbazide to form the semicarbazone. It has been established in separate experiments that the reaction of Schiff base with semicarbazide is fast. The detailed mechanism of the latter conversion is unknown. 

Normal nucleophilic substitution reactions of alkyl and aryl chloropyrazines have been examined as follows 2-chloro-3-methyl- and 3-chloro-2,5-dimethyl(and diethyl)pyrazine with ammonia and various amines (535, 679, 680) 2-chloro-3(and 6)-methylpyrazine with methylamine and dimethylamine (681, 844), piperidine and other amines (681, 921) 2-chloro-5(and 6)-methylpyrazine with aqueous ammonia (362) alkyl (and phenyl) chloropyrazines with ammonium hydroxide at 200° (887) 2-chloro-3-methylpyrazine with aniline and substituted anilines (929), and piperazine at 140° (759) 2-chloro-3-methyl(and ethyl)pyrazine with piperidine (aqueous potassium hydroxide at reflux) (930,931) [cf. the formation of the 2,6-isomer( ) (932)] 2-chloro-3,6-dimethylpyrazine with benzylamine at 184-250° (benzaldehyde and 2-amino-3,6-dimethylpyrazine were also produced) (921) 2-chloro-3,5,6-trimethylpyrazine with aqueous ammonia and copper powder at 140-150° (933) and with dimethylamine at 180° for 3 days (934,935) 2-chloro-6-trifluoromethylpyrazine with piperazine in acetonitrile at reflux (759) 2-chloro-3-phenylpyrazine with aqueous ammonia at 200° (535) 2-chloro-5-phenylpyrazine with liquid ammonia in an autoclave at 170° (377) 2-chloro-5-phenylpyrazine with piperazine in refluxing butanol (759) but the 6-isomer in acetonitrile (759) 5-chloro-2,3-diphenylpyrazine and piperidine at reflux (741) and 5-chloro-23-diphenylpyrazine with 2-hydroxyethylamine in a sealed tube at 125° for 40 hours (834). 

The hydrogenation of quinolines and isoquinoiines takes place in two distinct steps. The formation of the /y/-tetrahydro compound, 40 or 41, occurs under conditions used to saturate a nonfused pyridine ring (Eqn. 17.39).131-136 Further hydrogenation of the tetrahydroquinoline takes place using the standard conditions for the hydrogenation of aniline and substituted anilines. 

Aromatic amines (aniline and substituted anilines) are used as intermediates in industrial and pharmaceutical chemistry [11], Because of their aromatic character, they strongly absorb in the UV range. A recent study has shown the great interest for the study of aromatic amines from azo-dyes reduction using UV spectrophotometry [12], On the opposite, aliphatic amines do not absorb directly (see Section 4.2). 

Very interesting PHD polyols are obtained by the reaction in polyether media of TDI with primary amines and, instead of polymeric polyurea, organic diurea compounds are generated, insoluble in polyethers, in the form of a very fine dispersion. Example of amines used include ammonia, anilines and substituted anilines, and fatty amines (reactions 6.22 and 6.23). 

Aniline and substituted-anilines react with nitrous acid to form arenediazonium salts a diazonium group can be displaced by a nucleophile. Arenediazonium ions can be used as electrophiles with highly activated benzene rings to form azo compounds that can exist in cis and trans forms. Secondary amines react with nitrous acid to form nitrosamines. 

The activating effect of CN has been much studied in association with the activating effect of NO2 and heterocyclic N in the reactions of 2-chloro-3-cyano-5-nitropyridine (and related compounds) with aniline and substituted anilines and other amine nucleophiles in various solvents ". 2-Chloro-3-cyanopyridine is too unreactive for study, but the reaction of 2-chloro-5-nitropyridine with aniline in methanol gives a log k value of -5.31 at 40 °C For the corresponding reaction of 2-chloro-3-cyano-5-nitropyridine log k is -1.68, i.e. the activation by CN is by a factor of over 4000. The kinetics of the reactions of 2-fluoro-3-cyano-5-nitropyridine have also been studied. ... 

C.M. Knapp and J.J. Breen, Effects of tetraaUcylammonium salts on the micellar electrokinetic chromatography of aniline and substituted anilines, J. Chromatogr. A, 799, 289-299,1998. 

In most laboratories today, PAHs are routinely monitored under EPA Method 8270 and comprise the majority of neutrals under the Base, Neutral, Adds (BNAs) designation of the method (2). This is a liquid-liquid extraction method with determination by gas chromatography-mass spectrometry (GC MS). Careful changes in pH of the aqueous phase enables a selective extraction of bases and neutrals from acidic compounds. Examples of priority pollutant organic bases include aniline and substituted anilines. Examples of priority pollutant organic acids include phenol and substituted phenols. The most popular method of recent years has been EPA Method 525, which incorporates SPE techniques and is applicable to PAHs in drinking water (3). 

Condensation reactions of hydroquinone with aniline and substituted anilines are carried out industrially for the production of TV, A -diaryl-p-phenylenedia-mine. As with nitriles, conventional reagents like PTSA and chlorides of Al and Zn lead to stoichiometric reactions. Sulfated zirconia, used in the form of a slurry, on the other hand, is needed only in catalytic amounts, and has been shown (Kumbhar and Yadav, 1989) to be a very effective catalyst. 

In the presence of vanadium and molybdenum complexes, however, aniline and substituted anilines are reported to give rise to nitro compounds exclusively, equation... 

Phenols are so reactive toward electrophilic aromatic substitution that all unsubstituted positions ortho and para to the hydroxy group are brominated. The brominated compounds so formed are often solids and may be used as derivatives (Sec. 25.12E). Aniline and substituted anilines are also very reactive toward bromine and react analogously however, solubility tests are normally used to distinguish between anilines and phenols. 

Basicity of aniline and substituted anilines is discussed in Section 1.7.2... 

One of the most studied class of primary aniline derivatives are / -aminophenols. The /7-amino phenol-s(I) are reduced in a two-electron process in aqueous solution to form quinonemines(II). The quinonemines then hydrolyse to form the corresponding /7-quino-ne(III) (Scheme 12.3). The hydrolysis reaction suggests that this reaction should be pH dependent. Table 12.5 gives the half-wave potential of aniline and substituted anilines under various conditions. 

Tetramers of aniline (and substituted anilines) were optimized using the B3LYP functional with a 6-3IG basis set. The unit cell for polymer calculations was built from the tetramer structural data obtained above. In our calculations, a periodical, infinite and non-planar helical geometiy was assumed having the internal coordinates of one aniline unit, as shown in Fig. 2. We have studied the electronic properties of PANI only in its reduced form. Previous works have shown that PANI has a large band gap in the reduced state (around 3.6eV), which diminishes for the oxidized state. These effects were extensively analyzed using VEH and Extended HUckel methods [35]. 

Fig. 12. Structural formulas of aniline and substituted anilines investigated in the work reviewed herein.

Thble VI. Electrode Potentials E for the First Polymer Film Oxidation Step, Redox Potentials of the First Redox Step Eredox, RHE> 2nd Electronic Absorption Maxima A ax of the Reduced Form of Aniline and Substituted Anilines in Various Solutions of 1-M HCl [241] and of 1-M HCIO4 [239,240,456]... 

Roy RK, de Proft F, Geerlings P (1998) Site of protonation in aniline and substituted anilines in the gas phase a study via the local hard and soft acids and bases concept. J Phys Chem A 102(35) 7035-7040... 

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