Hydrogenations Using Platinum

8 Parts of ethyl l -(3-methoxyphenyl)-B-nitropropyl ether are dissolved in 135 parts of acetic acid, and 25 parts of 4N sulphuric acid, 1 part of 5% palladised charcoal and 0.3 part of platinum oxide are added to the resulting solution. The mixture is stirred in an atmosphere of hydrogen at a pressure of 100 atmospheres and at 18—23°C. until absorption is complete. The mixture is filtered and the filtrate is evaporated to small volume in vacuo. The residue is stirred with 

200 parts of water and 50 parts of ether. The aqueous layer is separated and evaporated to small volume in vacuo. 100 Parts of 4N sodium hydroxide are added to the residue and the mixture is extracted with 400 parts of ether. The ethereal extract is washed with saturated sodium chloride solution, dried and evaporated to dryness in vacuo. A solution of 12.9 parts of the residual oil thus obtained in 20 parts of acetone is added to a solution of 7.8 parts of oxalic acid dihydrate in 60 parts of acetone. When the separation of solid is substantially complete, the mixture is filtered and the residual solid is crystallised from a mixture of ethanol and ethyl acetate. There is thus obtained 2-ethoxy-2-(3-methoxyphenyl)-l-methylethylamine hydrogen oxalate, m.p. 142— 143°C. 

A mixture of 2 parts of 2-methoxy-2-(3-methoxyphenyl)ethylamine hydrochloride, 20 parts of saturated aqueous sodium chloride solution and 5 parts of 4N sodium hydroxide solution is extracted with 50 parts ether. The ether extract is washed with saturated aqueous sodium chloride solution, dried and evaporated. The residual oil consists of 2-methoxy-2-(3-methoxyphenyl)ethylamine. 

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Activation with platinum under a direct stream of hydrogen, using platinum as a catalyst. 

Sodium in ethanol has been used to reduce a 2//-pyrrole to the pyrrolidine,9,16 as has catalytic hydrogenation using platinum oxide.96 The latter method, however, took compound 80 only to the 3-pyrroline, as did sodium borohydride.71 Sodium borohydride reduction of the methiodide salt of 123 also gave a 3-pyrroline.119... 

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... 

They initially discovered several synthetically efficient routes to obtain the hexahydro-l,5-methanoazocino[3,4-f)]indole scaffold. For example, they found that treatment of the pyridine 222 with methyl iodide furnished the pyridinium salt 223, which could be hydrogenated using platinum oxide in ethanol to yield the piperidine 224 (Scheme 26). Oxidative cycHzation was then employed with mercury(II) acetate in a buffered aqueous medium to form iminium ion 225, which underwent subsequent cycHzation at the 2-position of the indole to furnish tetrahydrocarbazole 226. ... 

Sorbitol has been obtained synthetically from D-glucose by reduction with sodium amalgam and by pressure hydrogenation using platinum, Raney nickel, or Adkins-type nickel catalyst. It has also been obtained by the electrolytic reduction of glucose and by the pressure hydrogenation of gluconic lactones. 

The dehydration causes a double bond shift to the exocyclic position because of extension of conjugation. The alternative endocyclic structure, as demonstrated for dehydrated dihydrohumulinic acid (see 8.4.3.I.2.), does not occur. Catalytic hydrogenation using platinum on carbon yields the known compound 140 (Fig. 60) (see 8.4.3.I.2.2.). 

B. Corenwinder Reacted iodine with hydrogen using platinum Arm. Chim. Phy. 34(3), 77 (1S52) sponge. 

H. Debus Formed methylamine by reducing hydrogen Annalen. 128,200 (1863) cyanide with hydrogen using platinum black. Also reduced ethyl nitrite to ethyl alcohol and ammonia. 

Adams catalyst, platinum oxide, Pt02 H20. Produced by fusion of H2PtCl6 with sodium nitrate at 500-550 C and leaching of the cooled melt with water. Stable in air, activated by hydrogen. Used as a hydrogenation catalyst for converting alkenes to alkanes at low pressure and temperature. Often used on Si02... 

Nitro groups are readily reduced to primary amines by a variety of methods Cat alytic hydrogenation over platinum palladium or nickel is often used as is reduction by iron or tin m hydrochloric acid The ease with which nitro groups are reduced is especially useful m the preparation of arylamines where the sequence ArH ArN02 ArNH2 IS the standard route to these compounds... 

AH commercial processes for the manufacture of caprolactam ate based on either toluene or benzene, each of which occurs in refinery BTX-extract streams (see BTX processing). Alkylation of benzene with propylene yields cumene (qv), which is a source of phenol and acetone ca 10% of U.S. phenol is converted to caprolactam. Purified benzene can be hydrogenated over platinum catalyst to cyclohexane nearly aH of the latter is used in the manufacture of nylon-6 and nylon-6,6 chemical intermediates. A block diagram of the five main process routes to caprolactam from basic taw materials, eg, hydrogen (which is usuaHy prepared from natural gas) and sulfur, is given in Eigute 2. 

The gas is essentially inert to common materials of construction such as stainless steel under normal conditions of use. Platinum and gold are also not attacked by pure hydrogen chloride. 

Electrolysis of acidified water using platinum electrodes is a convenient source of hydrogen (and oxygen) and, on a larger scale, very pure hydrogen (>99.95%) can be obtained from the electrolysis of warm aqueous solutions of barium hydroxide between nickel electrodes. The method is expensive but becomes economical... 

Using a platinum catalyst, this reaction can now be carried out at temperatures as low as 40°C. The hydrogen used must be very pure traces of carbon monoxide can poison the catalyst. 

A procedure similar to that used in the investigation of the hydro-demethylation of xylenes was also employed in a study of the consecutive hydrogenation of phenol via cyclohexanone to cyclohexanol in gaseous phase on a platinum on silica gel catalyst (p. 27) at 150°C [scheme (VI)] at this temperature both reactions were irreversible under the excess hydrogen used. 

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. 

In technical hydrocarbon reforming processes using platinum catalysts, high hydrogen pressures are usually used to inhibit catalyst poisoning and coke formation as far as possible, for instance a total pressure of several atmospheres to several tens of atmospheres, with a several-fold excess of hydrogen in the reactant mixture. 

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