Elimination by hydrogen

Wm. Haynes The nickel carbide formation has been reversed. That is,nickel carbide has been eliminated by hydrogen treatment in some of the laboratory tests at the Bureau of Mines, and catalyst activity has been restored that way. In the pilot plant, however, we have not been able to achieve any such regeneration of the catalyst. 

The isopropylidene residue was then removed with very dilute hydrochloric acid and the product converted into benzyl 2,3-dimethyl-5-benzyl-L-rhamnofuranoside (LXI), from which the benzyl residues were eliminated by hydrogenation in the presence of palladium oxide. Treat-... 

The activation energy for the 7a Si at room temperature is 0.41 eV. This suggests that the shallow surface states have been largely eliminated by hydrogenating the c-Si surface. The log 7a Si versus 1 IT curve becomes linear at T a 150°C here 7sa = 1.05 eV, which is close to the band-gap value of c-Si. For 7ox, however, no such linearity is reached up to 200°C, beyond which a = 0.95 eV. This is another indication that the 7 and 7t components are much larger in 7ox than in 7a si. Therefore one can conclude that the a-Si H passivation has reduced both die deep surface state and the shallow surface state densities. 

Where necessary, the harmful nitrogen compounds can be removed by acid treatment (224,345) or the nitrogen can be selectively eliminated by hydrogenation (66). 

Amperometric detection of hydrogen peroxide suffers also from interferences from other oxidizable substances present in biological fluids (ascorbic acid, glutathione, cysteine, uric acid, bilirubin). These problems are eliminated by hydrogen peroxide-permselective membranes [197, 198], by simultaneous use of a non-enzymatic membrane electrode... 

A pair of samples were prepared in which the active sites on the growing propylene polymer were eliminated by hydrogen before addition of ethylene. Practically identical values for percentage of ethylene incorporation were calculated for both the hot and cold scans. These data are shown in Table 3.2. 

Present in citronella and valerian oils, tur penline, ginger, rosemary and spike oils. It is produced artificially by the elimination of hydrogen chloride from bornyl chloride (artifi cial camphor) or from isobornyl chloride, by the dehydrogenation of borneol and isobor-neol and by the action of elhanoic anhydride on bornylamine. Chiral. 

Finishing Processes that eliminate (most often by hydrogenation) undesirabie compounds. 

Purification of refinery gases by elimination of hydrogen sulfide as well as Claus units for sulfur recovery began to make their appearance. 

The majority of preparative methods which have been used for obtaining cyclopropane derivatives involve carbene addition to an olefmic bond, if acetylenes are used in the reaction, cyclopropenes are obtained. Heteroatom-substituted or vinyl cydopropanes come from alkenyl bromides or enol acetates (A. de Meijere, 1979 E. J. Corey, 1975 B E. Wenkert, 1970 A). The carbenes needed for cyclopropane syntheses can be obtained in situ by a-elimination of hydrogen halides with strong bases (R. Kdstcr, 1971 E.J. Corey, 1975 B), by copper catalyzed decomposition of diazo compounds (E. Wenkert, 1970 A S.D. Burke, 1979 N.J. Turro, 1966), or by reductive elimination of iodine from gem-diiodides (J. Nishimura, 1969 D. Wen-disch, 1971 J.M. Denis, 1972 H.E. Simmons, 1973 C. Girard, 1974),... 

Another alternative involves the use of a weak acid cation exchanger in the hydrogen form. This resin is not capable of removing aH cations. It removes only the amount equivalent to the bicarbonate in the influent water. The acidity in the effluent stream is carbonic acid [463-79-6] which can be eliminated by installing a degasifter. 

Preparation from Amines. The most common method of preparing isocyanates, even on a commercial scale, involves the reaction of phosgene [75-44-5] and aromatic or aUphatic amine precursors. The initial reaction step, the formation of N-substituted carbamoyl chloride (1), is highly exothermic and is succeeded by hydrogen chloride elimination which takes place at elevated temperatures. 

Phosphoms halides are subject to reactions with active hydrogen compounds and result in the elimination of hydrogen halide. They are convenient reagents in the synthesis of many esters, amides, and related compounds. However, because the involved hydrogen halide frequendy catalyzes side reactions, it is usually necessary to employ a hydrogen halide scavenger to remove the by-product. 

The manufacture and uses of oxiranes are reviewed in (B-80MI50500, B-80MI50501). The industrially most important oxiranes are oxirane itself (ethylene oxide), which is made by catalyzed air-oxidation of ethylene (cf. Section 5.05.4.2.2(f)), and methyloxirane (propylene oxide), which is made by /3-elimination of hydrogen chloride from propene-derived 1-chloro-2-propanol (cf. Section 5.05.4.2.1) and by epoxidation of propene with 1-phenylethyl hydroperoxide cf. Section 5.05.4.2.2(f)) (79MI50501). 

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