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Platinum nitrobenzenes

Phenylhydroxylamine rearranges in sulfuric acid to give mainly p-aminophenol. Industrial routes to this compound have been developed in which phenylhydroxylamine, formed by hydrogenation of nitrobenzene in sulfuric acid over platinum-on-carbon, is rearranged as it is formed. Conditions are adjusted so that the rate of rearran ment is high relative to the rate of hydrogenation of hydroxylamine to aniline (15,17,86). An easy way to obtain a favorable rate ratio is to carry out the reduction with about 1% DMSO present in the sulfuric acid (79,81). [Pg.107]

This reduction step can be readily observed at a mercury electrode in an aprotic solvent or even in aqueous medium at an electrode covered with a suitable surfactant. However, in the absence of a surface-active substance, nitrobenzene is reduced in aqueous media in a four-electron wave, as the first step (Eq. 5.9.3) is followed by fast electrochemical and chemical reactions yielding phenylhydroxylamine. At even more negative potentials phenylhydroxylamine is further reduced to aniline. The same process occurs at lead and zinc electrodes, where phenylhydroxylamine can even be oxidized to yield nitrobenzene again. At electrodes such as platinum, nickel or iron, where chemisorption bonds can be formed with the products of the... [Pg.397]

Rylander in Catalytic Hydrogenation Over Platinum Metals (p. 39, Academic Press, New York, 1967). Nitrobenzene in ethanol was hydrogenated at room temperature and 1 atm over various amounts of 5% Pd on carbon. Four loading levels of catalyst were used. At each level, the reduction was carried out in two different types of batch reactor. [Pg.532]

The method is applied for sensitive aromatic nitro compounds, as for example for o/p-substituted nitrobenzenes. The reduction proceeds with hydrazine/precious metal (platinum) catalysts. [Pg.188]

Ito [85] investigated the sonoelectropolymerisation of thiophene (0.3 mol dm ) in nitrobenzene using tertiary butyl perchlorate as the electrolyte, platinum electrodes... [Pg.211]

There are a few reports of poly(naphthalene) thin films. Yoshino and co-workers. used electrochemical polymerization to obtain poly(2,6-naphthalene) film from a solution of naphthalene and nitrobenzene with a composite electrolyte of copper(II) chloride and lithium hexafluoroarsenate. Zotti and co-workers prepared poly( 1,4-naphthalene) film by anionic coupling of naphthalene on. platinum or glassy carbon electrodes with tetrabutylammonium tetrafluoroborate as an electrolyte in anhydrous acetonitrile and 1,2-dichloroethane. Recently, Hara and Toshima prepared a purple-colored poly( 1,4-naphthalene) film by electrochemical polymerization of naphthalene using a mixed electrolyte of aluminum chloride and cuprous chloride. Although the film was contaminated with the electrolyte, the polymer had very high thermal stability (decomposition temperature of 546°C). The only catalyst-free poly(naphthalene) which utilized a unique chemistry, Bergman s cycloaromatization, was obtained by Tour and co-workers recently (vide infra). [Pg.295]

Reduction of aromatic nitro group takes preference to the reduction of the aromatic ring. Under certain conditions, however, even the benzene ring was reduced. Hydrogenation of nitrobenzene over platinum oxide or rhodium-platinum oxide in ethanol yielded aniline while in acetic acid cyclohexylamine was produced [55]. Heating of nitrobenzene with formic acid in the presence of copper at 200° gave a 100% yield of aniline, whereas similar treatment in the presence of nickel afforded 67% of cyclohexylamine [71]. [Pg.74]

Conversion of substituted nitrobenzenes to the arylhydroxylamine is easily achieved by reduction in neutral or slightly acid solution. In the first classical experiments, Haber [35] used a platinum cathode and ammonia ammonium chloride buffer and die process was improved by Brand [57] using either a nickel or silvered copper cathode in an acetate buffer. The hydroxylamine can also be obtained from reduction in dilute sulphuric acid provided tire temperature is kept below 15° C to suppress furtlier reduction [58]. This electrochemical route to arylhydroxylamines due to Brand is superior to the chemical reduction using zinc dust and ammonium chloride solution. The latter process is known to give variable yields depending on... [Pg.379]

Vavon and Husson G.R. clxxv. 277,1922) have likewise clearly demonstrated the existence of patches of varying activity in platinum black by showing that the progressive addition of a poison such as carbon disulphide will first inhibit. the catalytic hydrogenation of substances more difficult to hydrogenate such as acetophenone without appreciably affecting the activity in respect to hy ogena-tion of nitrobenzene which is readily reduced. [Pg.143]

When the apparently penta-coordinated diarsine complexes just described are dissolved in solvents more polar than nitrobenzene, they tend to dissociate into halide ions and bivalent cations, thus becoming 2 1 electrolytes (119). The effect is most marked with the platinum compounds. It has been shown that solvation effects might be less with platinum than with palladium, and so, other things in the equilibria being equal, it can also be concluded that the bonding of further ligands by a square-planar complex is much weaker with platinum than with palladium. Square-planar nickel complexes are of course the most ready to take up further ligands. [Pg.175]

Fig. 7.189. Colloidal platinum is sometimes regarded as a catalyst for the reduction of nitrobenzene in solution. A mixed potential alternative is shown. Fig. 7.189. Colloidal platinum is sometimes regarded as a catalyst for the reduction of nitrobenzene in solution. A mixed potential alternative is shown.
Aromatic nitro compounds can be converted to the corresponding 4-fluoroanilines if the 4-position carries a hydrogen atom. Thus, nitrobenzene can be converted to 4-fluoroaniline with 100% conversion and 95% selectivity by heating with hydrogen under pressure [platinum(IV) oxide catalyst] in the presence of boron trifluoride-diethyl ether complex at 42°C for 12.5 hours. 3-Chloro-l-nitrobenzene can be similarly hydrogenated-fluorinated to 3-chloro-4-fluoroaniline.25,26... [Pg.603]

An even more remarkable fact is that catalysts may be poisoned with respect to one reaction while retaining their activity with respect to other reactions. Vavon and Huson found that the hydrogenation of propyl ketone in presence of colloidal platinum was inhibited by amounts of carbon disulphide insufficient to prevent the hydrogenation of piperonal and nitrobenzene. Further amounts of carbon disulphide stopped the hydrogenation of piperonal but not that of nitrobenzene. [Pg.248]

With a platinum cathode in hydrochloric acid suspension nitrobenzene gives o- and p-chloraniline, but L8b3 has shown that with a lead cathode aniline is the only product. Probably o- and p-chloraniline result from the molecular re-arrangement of the chloramine, C Hfi - NHC1, which is produced from the phenylhydroxylamine first formed. Elbs and Silberman4 also found that, in acid solution, lead cathodes give more aniline than platinum when reducing nitrobenzene. [Pg.55]

Electrochemical functionalization - reductive coupling of diazonium salts The electrochemical functionalization of SWCNTs, deposited on an Si/Si02 substrate, with 4-nitrophenyl groups succeeded by the reduction of 4-nitrobenzene-diazonium salt in a mini-electrochemical cell with platinum counter and (pseu-do-)reference electrodes. A probe needle was used to make contact with one of the Au-Pd bonding pads on the substrate and allowed the application of an electric potential to the electrode (-1.3 V vs. Pt for >30 s) and to any SWCNTs underneath the electrode [177b]. [Pg.47]

Haussermann 2 reduced nitrobenzene and nitrotoluenes both in alkaline and acid solution, the former with iron, the latter with platinum, electrodes. By reduction in alkaline solution, he obtained as principal product hydrazobenzene and hydrazo-toluene respectively in sulphuric-acid solution he got from nitrobenzene, as chief products, benzidine sulphate and azoxy-benzene, besides an easily changeable body which was not further determined. o-Nitrotoluene3 under like conditions gave o-tolui-dine sulphate besides small quantities of o-toluidine p-nitro-toluene yielded principally p-toluidine. [Pg.136]

Noyes and Clement used concentrated sulphuric acid of 1.84 to 1.94 sp. gr. as a solvent for nitrobenzene. Gat ter-mann and Koppert had treated the sulphuric-acid solution before the reduction with a few drops of water. Noyes and Clement obtained from 50 g. nitrobenzene at platinum electrodes 30 g. anhydrous p-amidophenol-o-sulphonic acid, cor-... [Pg.137]

Lob2 found a reaction analogous to that of Gattermann when he reduced nitrobenzene in hydrochloric-acid solution or suspension, using platinum electrodes. [Pg.138]

Platinum and nickel electrodes behave alike in the experiments to reduce nitrobenzene in acid solution to benzidine. Carbon cathodes, on the contrary, give only little benzidine zinc and amalgamated zinc electrodes yield no, or extremely little, benzidine, while aniline, as already previously observed by Elbs, results as the principal product. [Pg.139]


See other pages where Platinum nitrobenzenes is mentioned: [Pg.628]    [Pg.163]    [Pg.115]    [Pg.628]    [Pg.491]    [Pg.698]    [Pg.114]    [Pg.136]    [Pg.295]    [Pg.99]    [Pg.381]    [Pg.164]    [Pg.163]    [Pg.105]    [Pg.927]    [Pg.628]    [Pg.65]    [Pg.325]    [Pg.28]    [Pg.150]    [Pg.953]    [Pg.277]    [Pg.95]    [Pg.56]    [Pg.115]    [Pg.122]    [Pg.85]    [Pg.174]    [Pg.168]    [Pg.168]    [Pg.50]    [Pg.137]   
See also in sourсe #XX -- [ Pg.481 ]




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