Hydrogenative addition

When treated with bromine or chlorine in aqueous solution alkenes are con verted to vicinal halohydrins A haloni um ion IS an intermediate The halogen adds to the carbon that has the greater number of hydrogens Addition is anti... 

Immobile hydrocarbon sources requite refining processes involving hydrogenation. Additional hydrogen is also requited to eliminate sources of sulfur and nitrogen oxides that would be emitted to the environment. Resources can be classified as mostiy consumed, proven but stiU in the ground, and yet to be discovered. A reasonable estimate for the proven reserves for cmde oil is estimated at 140 x 10 t (1.0 x 10 bbl) (4). In 1950 the United States proven reserves were 32% of the world s reserve. In 1975 this percentage had decreased to 5%, and by 1993 it was down to 2.5%. Since 1950 the dominance of... 

C. Sacco, "Quad Cities Unit 2 Incore Hydrogen Addition Test Results," presented at 1994INPO-EPRJ Chemistry Managers Workshop. Atlanta, Ga.,... 

Bitumen is a hydrogen-deficient oil that is upgraded by carbon removal (coking) or hydrogen addition (hydrocrackiag) (2,4). There are two methods by which bitumen conversion can be achieved by direct heating of mined tar sand and by thermal decomposition of separated bitumen. The latter is the method used commercially, but the former has potential for commercialisation (see Fuels, SYNTHETIC). 

Hydrogen can be added to the aromatic stmctures converting them to hydroaromatic rings. The hydrogen addition and removal is generally but not entirely reversible (24). 

Conversion of 4 to 6 consumes no hydrogen and appears to be a consequence of double-bond migration. In this case, however, the reaction proceeded in two stages, hydrogen addition (5) followed by hydrogen elimination and migration (2S). 

Hydrogenation of aromatics under mild conditions gives mainly the all-cis isomer as if hydrogen addition takes place from only one side of the molecule (23,24). Reductions under more vigorous conditions may give other isomers by isomerization of the initially formed all-cis product. Under mild conditions, other isomers are accounted for by desorption and readsorption in a new orientation of intermediate olefins, as well as by double-bond migration in the... 

Before hydrogen addition to ensure complete carbon monoxide conversion. c Saturated at 30 in. mercury and 15.6° C nitrogen-free basis. d Total gas composition = 100.00%. 

Total feed from caustic scrubber Hydrogen addition First-stage fresh feed First-stage recycle Second-stage fresh feed Second-stage recycle Product gas... 

The attack of a nucleophile on a carbonyl group can result in substitution or addition (Chapter 16), though the first step of each mechanism is the same. The main factor that determines the product is the identity of the group X in RCOX. When X is alkyl or hydrogen, addition usually takes place. When X is halogen, OH, OCOR, NH2, and so on, the usual reaction is substitution. 

These findings were further confirmed by data collected under isothermal conditions. Upon hydrogen addition at 350°C on the physical mixture previously saturated with NO species at the same temperature, no reaction products were detected. This indicated that the stored nitrates could not be regenerated by H2 at constant temperature, i.e. without a prior release in the gas phase. 

The afterglow data of Gougousi et al. have two features that need to be explained The first is the observation (a), also made by Adams et al. and Smith and Spanel, that the deionization coefficient f) declines with increasing time. The other observation (b) is that hydrogen addition enhances the rate of deionization. 

More recently homogeneous hydrogenation catalysts, such as RhCl(Ph3P)3, have been developed which are soluble in the reaction medium. These are believed to transfer H to an alkene via a metal hydride intermediate they, too, lead to a considerable degree of SYN stereoselectivity in hydrogen addition. 

Hydrogen addition and exchange reactions between a bituminous coal and a donor solvent or a nondonor solvent were investigated using fully-deutrated Tetralin and naphthalene. In the experiments conducted with coal, Tetralin-di2 and deuterium at 400°C, the ratio of hydrogen exchange to addition was on the average 2.0. 

In the two previous sections, evidence has been presented concerning the chemisorbed states formed when benzene interacts with metal surfaces. It is not the intention in this Section to discuss benzene hydrogenation in detail, but rather to enquire whether studies of this hydrogen-addition reaction provide information about the chemisorbed state of benzene. 

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