Benzene-, sodium platinum

Selective hydrogenation of quinolines and isoquinolines. Catalytic hydrogenation of quinolines and isoquinolines usually occurs preferentially in the pyridine ring. However, if the hydrogenation is conducted in trifluoroacetic acid, the reverse situation obtains and the benzene ring is reduced more rapidly. The same result can be obtained with mineral acids, but such hydrogenations are much slower. Both 2- and 4-phenylpyiidine can also be reduced preferentially in the benzene ring. Platinum oxide or palladium or rhodium catalysts can be used. Further reduction of 5,6,7,8-tetrahydroquinolines with sodium and ethanol provides a convenient route to rrans-decahydroquinolines. 

Isoquinoline can be reduced quantitatively over platinum in acidic media to a mixture of i j -decahydroisoquinoline [2744-08-3] and /n j -decahydroisoquinoline [2744-09-4] (32). Hydrogenation with platinum oxide in strong acid, but under mild conditions, selectively reduces the benzene ring and leads to a 90% yield of 5,6,7,8-tetrahydroisoquinoline [36556-06-6] (32,33). Sodium hydride, in dipolar aprotic solvents like hexamethylphosphoric triamide, reduces isoquinoline in quantitative yield to the sodium adduct [81045-34-3] (25) (152). The adduct reacts with acid chlorides or anhydrides to give N-acyl derivatives which are converted to 4-substituted 1,2-dihydroisoquinolines. Sodium borohydride and carboxylic acids combine to provide a one-step reduction—alkylation (35). Sodium cyanoborohydride reduces isoquinoline under similar conditions without N-alkylation to give... 

Similarly to quantitative determination of high surfactant concentrations, many alternative methods have been proposed for the quantitative determination of low surfactant concentrations. Tsuji et al. [270] developed a potentio-metric method for the microdetermination of anionic surfactants that was applied to the analysis of 5-100 ppm of sodium dodecyl sulfate and 1-10 ppm of sodium dodecyl ether (2.9 EO) sulfate. This method is based on the inhibitory effect of anionic surfactants on the enzyme system cholinesterase-butyryl-thiocholine iodide. A constant current is applied across two platinum plate electrodes immersed in a solution containing butyrylthiocholine and surfactant. Since cholinesterase produces enzymatic hydrolysis of the substrate, the decrease in the initial velocity of the hydrolysis caused by the surfactant corresponds to its concentration. Amounts up to 60 pg of alcohol sulfate can be spectrometrically determined with acridine orange by extraction of the ion pair with a mixture 3 1 (v/v) of benzene/methyl isobutyl ketone [271]. 

V-Acylsaccharins prepared by treatment of the sodium salt of saccharin with acyl chlorides were reduced by 0.5 molar amounts of sodium bis(2-methoxyethoxy)aluminum hydride in benzene at 0-5° to give 63-80% yields of aliphatic, aromatic and unsaturated aldehydes [1108 Fair yields (45-58%) of some aliphatic aldehydes were obtained by electrolytic reduction of tertiary and even secondary amides in undivided cells fitted with platinum electrodes and filled with solutions of lithium chloride in methylamine. However, many secondary and especially primary amides gave 51-97% yields of alcohols under the same conditions [130]. 

The isomer distribution obtained from the oxidation of mesitylene in acetic acid, sodium acetate depends on the anode material. Graphite strongly favours nuclear substitution to side chain substitution in the ratio 23 1 while at platinum this ratio is 4 1. Oxidation of methyl benzenes in acetic acid containing tetrabutykmmonium fluoroborate and no acetate ion gives benzyl acetate as the major product since loss of a proton from the radical-cation is now faster than nuclear substitution by acetic acid as the only nucleophile present [39]. 

In aqueous acetic acid, the disproportionation of the platinum still occurs quite rapidly, and it can be suppressed further by adding mineral acid. Hydrochloric acid is often used, but this has a disadvantage in that the exchange rate is inversely proportional to the chloride ion concentration. Perchloric acid has been found to be more satisfactory (55). The platinum(II) catalyst most used is sodium or potassium tetrachloropla-tinate(II). An aromatic compound added to the reaction mixture also inhibits disproportionation of the platinum(II) complex—benzene, pyrene, and other aromatics have been used. A comparative study of the effect of various aromatics on the H—D exchange in alkanes has been carried out (55). Even under optimum conditions, the disproportionation [Eq. (4)] still takes place, and the catalytic platinum(II) is slowly removed from the reaction mixture. To get useful rates of exchange in alkanes, temperatures of 100° to 120°C have to be used, and the disproportionation rate increases with temperature. 

In the reduction of nitrobenzene in a 2% aqueous sodium-hydroxide solution, according to previous publications, azoxy-benzene is formed at platinum and nickel electrodes, azobenzeno at lead, tin, and zinc cathodes, and aniline at copper cathodes especially in the presence of copper powder. It was found that, in an unchangeable experimental arrangement, a cathodo potential of 1.8 volts, as measured in connection with the deci-normal electrode, could be carried out with all the chosen cathodes and additions. At this constant potential, by using different metals and adding various metallic hydroxides, the whole reduction was carried out and the nature and quantity of the reduction products determined in each case. It turned out that the emphasized differences in the results disappeared and that, with an equal potential of all cathodes, similar yields of azoxybenzene and aniline and traces of azobenzene resulted. The cathodes were of platinum, copper, copper and copper powder, tin, platinum with addition of stannous hydroxide zinc, platinum with addition of zinc hydroxide, lead, platinum with addition of lead hydroxide, and nickel. The yields of azoxybenzene varied from 41-65% of aniline 23-53%. 

The Effect of Surfactants on the Yields Obtained In Electrooxidations on Platinum Electrodes In Benzene-2M Aqueous Sodium Ifydroxlde Ehiulslons ... 

Benzene and aikyibenzenes are quantitatively converted to cyclohexanes by catalytic hydrogenation. Modem procedures employ liquid-phase hydrogenation over nickel catalysts at 100-200° or over platinum catalysts at room temperature. Nickel catalysts are poisoned by traces of thiophene and water. Small quantities of hydrogen halide increase the effectiveness of platinum catalysts. Isomerization occurs during the reduction of benzene over nickel at 170° the cyclohexane formed is probably contaminated with methylcyclopentane, Partial reduction of benzene to 1,4-dihydrobenzene is accomplished by sodium in liquid ammonia at —45°. ... 

To a solution of 24.4 g. (0.20 mole) of salicylaldehyde in 100 ml, of 95% ethanol are added 0.5 ml. of 2 If aqueous ferrous chloride solution and 0.1725 g. of platinum oxide catalyst [Org. Syntheses Coll. Vol. 1, 463 (1941)]. The mixture is shaken under a pressure of 3 atm, of hydrogen in a low-pressure hydrogenation apparatus [Org. Syntheses Coll. Vol. 1, 61 (1941)]. The absorption of hydrogen is complete in 1 hour. To the mixture is added 0.4 ml. of 1 iV aqueous sodium hydroxide solution, and the catalyst is recovered by filtration of the mixture. The solvent is removed from the filtrate by evaporation under vacuum, and the solid residue is recrystallized from 150 ml. of hot benzene. There is obtained a 92% yield of o-hydroxybenzyl alcohol as white crystals, m.p. 84.5-85°. 

Electrolytic reduction of o-nitroj)heny arsinic acid in a sodium acetate solution, using a water-cooled platinum eathohydrazo-benzene-o-o -dlarsinicacid,(HO)ijOAs.Ceir4.Nir.NHf.C,ir4.AsO(OII)2,... 

Bis(AOV-diethyldiselenocarbamato)platinum(II) (0.58 g, 0.88 mmole) and Pt(PPh3)2Cl2 (0.66 g, 0.83 mmole) are mixed in 35 mL benzene (refluxed over sodium benzophenone ketyl before use). The mixture is refluxed under nitrogen for about 7 hours. A clear, yellow solution is formed. The solution is evaporated to dryness in the hood. The yellow solid is recrystallized from CHC13/ heptane. Yield, 1.0 g (81%), m.p. 205-8°.13... 

It is probable that tetrachloro(diethyIene)diplatinum(II) was first prepared by Zeise by decomposition of trichloro-(ethylene)platinic(II) acid.1 Boiling hexachloroplatinic-(IV) acid with chloroform also gave the compound.2 However, it was first obtained in sufficient quantity for investigation by Anderson,3 who boiled an ethanolic solution of sodium hexachloroplatinate(IV) 6-hydrate until reduction to platinum(II) was complete. This procedure is tedious, and the yields are affected markedly by impurities in the platinum salt and by the presence of other platinum metals.4 Optimum yields of 75% are obtained only after much experience. The general method of Kharasch and Ashford,5 involving adding an olefin to a suspension of platinum(IV) chloride in warm benzene or glacial acetic... 

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