Alkyl isomerization

In contrast to triphenylphosphine-modified rhodium catalysis, a high aldehyde product isomer ratio via cobalt-catalyzed hydroformylation requires high CO partial pressures, eg, 9 MPa (1305 psi) and 110°C. Under such conditions alkyl isomerization is almost completely suppressed, and the 4.4 1 isomer ratio reflects the precursor mixture which contains principally the kinetically favored -butyryl to isobutyryl cobalt tetracarbonyl. At lower CO partial pressures, eg, 0.25 MPa (36.25 psi) and 110°C, the rate of isomerization of the -butyryl cobalt intermediate is competitive with butyryl reductive elimination to aldehyde. The product n/iso ratio of 1.6 1 obtained under these conditions reflects the equihbrium isomer ratio of the precursor butyryl cobalt tetracarbonyls (11). 

Tanabe and Hdlderich (1999) have given an extensive statistical survey of industrial processes using solid acids/bases as catalysts. Over 300 solids and bases have been covered. A variety of reactions like alkylation, isomerization, amination, cracking, and etherification with catalysts like zeolites, oxides, complex oxides, phosphates and ion-exchange resins have been covered. Over 120 industrial processes are referred with 180 different catalysts. 

Then, contrary to what was reported previously, the olefin dissociates from the zirconium metal complex. This conclusion was further supported by other experimental observations. However, it cannot be completely excluded that competition between dissociative and direct rearrangement pathways could occur with the different isomerization processes studied up to now. Note that with cationic zirconocene complexes [Cp2Zr-alkyl], DFT studies suggest that Zr-alkyl isomerizations occur by the classical reaction route, i.e. 3-H transfer, olefin rotation, and reinsertion into the Zr-H bond the olefin ligand appears to remain coordinated to the Zr metal center [89]. 

Industrial applications of zeolites cover a broad range of technological processes from oil upgrading, via petrochemical transformations up to synthesis of fine chemicals [1,2]. These processes clearly benefit from zeolite well-defined microporous structures providing a possibility of reaction control via shape selectivity [3,4] and acidity [5]. Catalytic reactions, namely transformations of aromatic hydrocarbons via alkylation, isomerization, disproportionation and transalkylation [2], are not only of industrial importance but can also be used to assess the structural features of zeolites [6] especially when combined with the investigation of their acidic properties [7]. A high diversity of zeolitic structures provides us with the opportunity to correlate the acidity, activity and selectivity of different structural types of zeolites. 

McPherson, L. J., and M. F. Olive. 1992. Alkylation, isomerization, polymerization, hydrotreatment and sulfur production. In Modern Petroleum Technology, ed. G. D. Hobson, pp. 517-575, London Institute of Petroleum. 

Base-catalyzed carbanionic alkylation, isomerization, polymerization reactions are of major significance. Base-catalyzed alkylation of alkylarenes, in contrast to acid-catalyzed ring alkylation, leads to alkylation of the side chain in the benzylic position [Eq. (1.28) see also Chapter 5] of particular interest is the alkylation of toluene to ethylbenzene (for styrene production). 

Preliminary observations indicate that the resulting secondary alkyls isomerize cleanly to the corresponding n -alkyls in dichloromethane-methanol, suggesting that the hydride ligand in the presumed cationic hydrido-olefin intermediate must return to the olefin more rapidly than it undergoes reductive elimination with the cr-alkyl or o -phenyl... 

Know the meaning of cracking, alkylation, isomerization, platforming, and octane number as applied to petroleum refining. 

The pioneer work in this field was carried out on polystyrene-supported acid catalysts [161]. Thereafter, several works on the use of sulfonic, strong acidic cation exchangers as acid catalysts were reported for alkylation, hydration, etherification, esterification, cleavage of ether bonds, dehydration, and aldol condensation [162,168-171], Besides, industrial applications of these materials were evaluated with reactions related to the chemistry of alkenes, that is, alkylation, isomerization, oligomerization, and acylation. [163,169], Also, Nation, an acid resin which has an acid strength equivalent to concentrated sulfuric acid, can be applied as an acid catalyst. It is used for the alkylation of aromatics with olefins in the liquid or gas phases and other reactions however, due to its low surface area, the Nation resin has relatively low catalytic activity in gas-phase reactions or liquid-phase processes where a nonpolar reactant or solvent is employed [166],... 

Nafion-H whose acid strength is —12 is active lor diversified organic reactions such as alkylation isomerization, disproportionation, transalkylation acyla lion, nitration, hydration, rearrangement etc [1 5] Since Nafion-H can be used m aqueous solution it is a useful catalyst... 

The satnrated hydrocarbons are used in industry as fuels, lubricants, and solvents. After nndergoing processes of alkylation, isomerization, and dehydrogenation, they also act as starting materials for the synthesis of paints, protective coatings, plastics, synthetic rnbber, resins, pesticides, synthetic detergents, and a wide variety of petrochemicals. The fnels, lubricants, and solvents are mixtures that may contain many different hydrocarbons... 

As indicated earlier (2,3) for sulfuric acid alkylations, the rates of reaction for olefins are often higher during the initial stages of alkylation than the rates of reaction for Isobutane. In the case of n-butenes, isomerization of the n-butenes occurs readily in the presence of sulfuric acid, see Reactions H-1 and H-2. Considerable information on these isomerizations were reported earlier (5) the rates of isomerization Increase as the amounts of excess acid or as the acidity of the acid phase increase. Certainly at the conditions employed in commercial alkylators, isomerization would be very rapid. 

Finally, the mechanism in Scheme 3 bears a resemblance to that presented above for the nickel-catalyzed reaction of methylmagnesium bromide and aryl bromides. However, there are outstanding differences between iron and nickel in their abilities to effect cross coupling reactions. Iron is a catalyst which is effective at lower temperatures and concentrations than used with nickel. Even more importantly, cross coupling can be effected completely stereospecifically with an iron catalyst and no alkyl isomerization of the Grignard component has been observed, in contrast to the nickel-catalyzed reactions. 

Metal oxide catalysts can be classified as oxides of transition elements or as oxides of other typical metals. Typical transition elements include Cr, Fe, Co, Mo, and V, whose oxides catalyze oxidation and reduction reactions by changing the oxidation state of the metal ion. For selective oxidation of hydrocarbons, mixed oxides containing Mo and V are widely used. Oxides of other metals (acidic oxides such as silica and silica-alumina, basic oxides such as CaO and MgO, and amphoteric oxides such as alumina) catalyze acid or base reactions such as alkylation, isomerization, and hydration-dehydration. 

Alkylation, isomerization Zeolite, silica-alumina, Pt-S04 /Zr02, etc. 

Ph3Sb)W[C(OR)Ph] is the only product. On heating in solution, cis-(CO)4LM-[C(OR)R ] (M = Cr, W L = phosphine R = Me, Et R = alkyl) isomerizes to yield a solution containing an equilibrium mixture of both cis and trans isomers. The equilibrium ratio of cis to trans isomers varies depending on the steric requirements of the carbene and phosphine ligand, on the central metal and on the solvent used. The isomers can be separated by column chromatography. ... 

Oare earth forms of zeolites X and Y type faujasites possess superior catalytic properties for various reactions such as alkylation, isomerization, and cracking (9, 12, 18). Structural studies involving x-ray diffraction and CO chemisorption have been made to locate the positions of the rare earth (11, 14, 16). Hydroxyl groups and their relationship to surface acidity have been studied by infrared spectroscopy, utilizing the adsorption of pyridine and other basic molecules (2, 6, 21, 22, 23). Since much of the previous research has involved measurements on mixed rare earth faujasites, a need existed for a more systematic study of the individual rare earth zeolites, in regard to both structural and catalytic properties. The present investigation deals with the Y, La, Ce, Pr, Sm,... 

Oxetane, 2-( o -chlorobenzyl)-2-phenyl-X-ray crystal structure, 7, 366 Oxetane, 3-chloromethyl-3-ethyl-ring strain, 7, 370-371 Oxetane, 2-(o-chlorophenyl)- H NMR, 7, 367 Oxetane, 2-cyano-synthesis, 7, 391-392 Oxetane, 2-cyano-3,3-dimethyl-2-phenyl-thermolysis, 7, 372 Oxetane, 2,2-dialkoxy-synthesis, 7, 396 Oxetane, 2,2- alkyl-isomerization, 7, 377 Oxetane, 3,3-dialkyl-alky lative cleavage, 7, 381 polymers, 7, 382 Oxetane, 2-diethylamino-synthesis, 7, 390 Oxetane, 3,3-difluoro-molecular dimensions, 7, 365 Oxetane, 2,2-dimethyl-mass spectra, 7, 368-369 photolysis, 7, 373 synthesis, 7, 393 Oxetane, 2,3-dimethyl- H NMR, 7, 366 thermolysis, 7, 372 Oxetane, 2,4-dimethyl-mass spectrum, 7, 369... 

Excellent surveys of olefin hydration, alkylation, isomerization, poljmieri-zation, disproportionation, hyorocar-bon separation, coordination compounds etc. 

Use Catalyst in alkylation, isomerization, condensation, dehydration, and polymerization reactions fluorinating agent in organic and inorganic reactions production of fluorine and aluminum fluoride additive in liquid rocket propellants refining of ura-... 

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