Adams hydrogenation

Finely divided (catalytic) forms of platinum are hazardous to handle if allowed to dry. Used Adams hydrogenation catalyst exploded while being sieved in air. It had been well washed, finally with water, and then air dried [1]. Manipulation of used catalyst on filter paper caused a violent explosion [2], The explosive catalysed oxidation of adsorbed hydrogen is suspected here. 

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... 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

Hydrocinnamic acid may also be prepared by the reduction of cinnamic acid with sodium and alcohol or with sodium amalgam or with hydrogen in the presence of Adams platinum oxide catalyst (Section 111,150) ... 

Very selective c/s-hydrogenations are also achieved by reduction with diiminc (N2H2, S. Hiinig, 1965 C.E. Miller, 1965 D.J. Pasto, 1991). The reagent can be used at low temperatures and has been employed in the selective reduction of C C double bonds, e.g. in the presence of a sensitive peroxidic function (W. Adam, 1978). 

Cyclopropane rings are opened hydrogenolytically, e.g., over platinum on platinum dioxide (Adam s catalyst) in acetic acid at 2 - 4 bars hydrogen pressure. The bond, which is best accessible to the catalyst and most activated by conjugated substituents, is cleaved selectively (W.J. Irwin, 1968 R.L. Augustine, 1976). Synthetically this reaction is useful as a means to hydromethylate C—C double bonds via carbenoid addition (see p. 74f. Z. Majerski, 1968 C.W. Woodworth, 1968). 

For more selective hydrogenations, supported 5—10 wt % palladium on activated carbon is preferred for reductions in which ring hydrogenation is not wanted. Mild conditions, a neutral solvent, and a stoichiometric amount of hydrogen are used to avoid ring hydrogenation. There are also appHcations for 35—40 wt % cobalt on kieselguhr, copper chromite (nonpromoted or promoted with barium), 5—10 wt % platinum on activated carbon, platinum (IV) oxide (Adams catalyst), and rhenium heptasulfide. Alcohol yields can sometimes be increased by the use of nonpolar (nonacidic) solvents and small amounts of bases, such as tertiary amines, which act as catalyst inhibitors. 

The Air Force Dispersion Assessment Model (ADAM -1980s) calculates the source term and dispersion of accidental releases of eight specific chemicals chlorine, fluorine, nitrogen tetroji ogen sulfide, hydrogen fluoride, sulfur dioxide, phosgene, and ammonia. It Ut a ... 

Forsyth et al. found that gelsemicine contains three active hydrogen atoms (Zerewitinov determination), yields a non-basic, monobenzoyl derivative, m.p. 232°, and behaves as a secondary base giving JV-methyl-gelsemicine hydriodide, m.p. 227°, on treatment with methyl iodide. It does not react with either hydroxylamine or 2 4-dinitrophenylhydrazine. On hydrogenation in dry acetic acid in presence of Adams s platinic oxide catalyst it absorbs three molecules of hydrogen. 

Cyanohydrin (52b 5 g mp 160-164°) is dissolved in acetic acid (200 ml) and placed in a 2-liter hydrogenation flask. Adams catalyst (0.75 g) is added (for 100 g cyanohydrin use 7.5 gof catalyst) and the mixture is hydrogenated until the theoretical amount of hydrogen is taken up (477 ml). The catalyst is removed by filtration, the filtrate is transferred to a 600 ml beaker provided with a stirrer and thermometer, treated with water (20 ml) and cooled to 0° (ice-salt). A solution of sodium nitrite (10 g) in water (30 ml) is added dropwise with stirring at 0°. The reaction mixture is then stirred for additional 2 hr at room temperature, treated with water (100 ml) and, after standing overnight, the precipitate is collected by filtration. The product is dissolved in ether (50 ml), the ether solution is washed sequentially... 

Hydrogenation with Adams catalyst took place only with the 6-alkyl derivatives. Dioxohexahydrotriazine itself acted as a catalyst poison (in common with 1,3,5-triazine and cyanuric acid ). Dioxo-tetrahydrotriazine as well as its A-alkyl and 6-alkyl derivatives can be readily hydrogenated by using Raney nickel. ... 

Oxidation of the hexahydro to tetrahydro derivatives was mentioned in connection with the synthesis of 3,5-dioxo-l,2,4-triazines (e.g., Section II,B,2,a). The reverse procedure, hydrogenation of the tetrahydro derivatives, was used with 6-azauracil, 6-azathymine, and their iV-methyl derivatives. With all these compounds hydrogenation proceeds smoothly in the presence of Adams catalyst. Only the hydrogenation of l-methyl-6-azathymine was not successful. ... 

Anhydro-bases derived from quaternary )S-carbolinium salts are reduced to p /r-A-substituted-l,2,3,4-tetrahydro-j8-carboline derivatives on hydrogenation over Adams catalyst in methanol solution made alkaline to ensure the presence of anhydro-base. ... 

Support for this suggestion comes from many quarters. Reduction of the jS-carboline anhydro-bases with sodium and alcohol or with tin and hydrochloric acid gives the 1,2,3,4-tetrahydro derivatives, as does catalytic reduction over platinum oxide in an alkaline medium. On the other hand, catalytic reduction with platinum oxide in acetic acid results in the formation of the 5,6,7,8-tetrahydro-j3-carbolinium derivatives (see Section III,A,2,a). It should be noted, however, that reduction of pyrido[l,2-6]indazole, in which the dipolar structure 211 is the main contributor to the resonance hybrid, could not be effected with hydrogen in the presence of Adams catalyst. 

A novel synthesis of 2-aminoquinoxalin-3-one 1-oxide has been effected by the hydrogenation of o-nitro-l-cyanoformanilide in ethanol in the presence of Adam s catalyst.- ... 

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