Platinum aliphatic nitro compounds

Ruthenium is commonly used with other platinum metals as a catalyst for oxidations, hydrogenations, isomerizations, and reforming reactions. The synergetic effect of mixing ruthenium with catalysts of platinum, palladium, and rhodium lias been found for the hydrogenations of aromatic and aliphatic nitro compounds, ketones, pyndine, and nitriles. 

Under suitable conditions it is possible to isolate the A-substituted hydroxylamines that are formed as intermediates in the reduction of nitro compounds. For this purpose it is essential in the reduction of aromatic nitro compounds to work with neutral or nearly neutral solutions suitable reducing agents are hydrogen and platinum oxide catalysts in glacial acetic acid,82,83 zinc dust in ammonium chloride solution,84 aluminum amalgam,85 and ammonium sulfide.86 Aliphatic nitro compounds may be reduced as their alkali salts (nitronates) by diborane in tetrahydrofuran, then giving A-alkylhydroxyl-amines 87 for instance, A-cyclohexylhydroxylamine is thus obtained from nitrocyclohexane in 53% yield. However, aliphatic nitro compounds are converted into A-alkylhydroxylamines more simply by catalytic hydrogenation in the presence of palladium-barium sulfate unlike aromatic nitro compounds, aliphatic nitro compounds require an acid medium for reduction to hydroxylamines an oxalic acid medium has proved the most suitable. 

This catalyst has been optimized over the years [80-82], and the best support was found to be acetylene black due to its highly olefinic nature. Palladium was initially chosen as the main catalytic metal, due to its high activity and low cost. This was improved by promoting it with a small amount of platinum however, this catalyst was too active and yielded unwanted side products via reactions such as ring hydrogenation. The selectivity of this catalyst was then corrected by the addition of iron oxide, which impeded the undesired reactions. Iron has also been proven to be a promoter for the hydrogenation of aliphatic nitro compounds [83]... 

Hydrogenation of nitro compounds is rather straightforward, and palladium, platinum, and nickel catalysts have been used. Palladium is the most common catalyst for both aromatic and aliphatic nitro compounds. The poor results obtained for reduction of aromatic nitriles with hydride reagents (sec. 4.2.C.iii) make catalytic hydrogenation the preferred method. Reduction of 407 involved conversion of the aromatic nitrile moiety to the benzylamine derivative when palladium and a trace of platinum oxide was used. Hydrogenation using platinum oxide converts aromatic nitro compounds to aniline derivatives, even in the presence of other reducible groups. OS... 

Aliphatic, nonconjugated niiroolehns can be reduced to the saturated nitro compound without difficulty (30y36a,40,76). Both platinum and palladium have been used. The reverse selectivity seems not to have been reported. 

Nitro Compounds. Under mild conditions, aromatic nitro compounds are hydrogenated easily to amines.518 The reaction may give partially reduced products, according to the circumstances. Palladium, platinum, and nickel are used frequently for this reaction. For example, nitro and benzyl ester functions are reduced on Pd(OH)2/C on THF and on Pd/C in EtOH.519 Aliphatic nitro groups are reduced more slowly. 

Aliphatic nonconjugated nitroalkenes can be reduced to the saturated nitro compounds without difficulty using platinum or palladium catalysts. A similarly situated alkynic group too is reduced selectively using Pd. 

Deuterium gas exchanges rapidly with methanol over Adams platinum catalyst at 35 . The influence of catalyst weight and treatment and of deuterium pressure on this exchange have been studied, as well as the effects of several aromatic, aliphatic, and olefinic nitro and related compounds. All of these nitro compounds reduce the rate of the exchange reaction initially, and the magnitude of such reduction increases with increasing specific rate constant for the platinum catalyzed hydrogenation of these compounds. 

BZ was al so partially oxidized by Ag(II) in a small H-cell with stationary platinum electrodes. Compounds identified in anolyte extracts included phenol, hydroquinone, benzoquinone, benzaldehyde, benzoic acid, methyl benzoate, benzonitrile, benzonitrile aldehyde, and 4-nitro butylnitrile. The yellow color of the anolyte was probably due to benzoquinone, which had a relatively high concentration. A compound which was tentatively identified as benzoquinone epoxide ( 11403) was present at the highest concentration and is believed to be a product of the oxidation of benzoquinone. Numerous nitrated aromatics were also detected and include nitrobenzene, dinitrobenzene isomers, nitrophenol isomers, and dinitnophenol isomers. Intermediates are summarized in Table 3 and classified as I. BZ substrate II. nitrated BZs HI. phenols, quinones, and epoxides IV. nitrated phenols V. BZ substituted with aliphatic and aromatic... 

EC is most often used in the analysis of catecholamines and aromatic amines, since these compounds are easily oxidized at low potentials (Table 1). However, most alkaloids also contain oxidizable functional groups, and are well suited for oxidative EC detection. Many contain either a phenol group or an indole nucleus, and even more contain a tertiary aliphatic amine. In addition, many aliphatic alcohols and amines, which are oxidized at high potentials on carbon electrodes, can be detected at much lower potentials with gold or platinum electrodes (Sect. 2.4). Alkaloids, however, do not usually contain easily reducible groups like quinones or aromatic nitro groups. 

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