Reactions of Unsaturated Hydrocarbons

The alicyclic secondary alcohol, cycZohexanol, may be dehydrated by concentrated sulphuric acid or by 85 per cent, phosphoric acid to cyciohexene. It has a higher boiling point (82-83°) than amylene and therefore possesses some advantage over the latter in.the study of the reactions of unsaturated hydrocarbons. 

Studies of the interaction of acetylenes with zinc oxide clearly provide a very interesting avenue for more detailed study. Results to date, though still very fragmentary, suggest that the view that reactions of unsaturated hydrocarbons over zinc oxide occur via proton abstraction to form a species with considerable anionic character has considerable merit. 

This review has been concerned largely with interactions and reactions of unsaturated hydrocarbons with zinc oxide. The picture of the active site as a metal oxide pair capable of heterolytic fission of an acidic C—H bond provides a consistent framework for discussion of these results. We believe this view may be generally applicable. In its application, however, we must keep in mind that zinc oxide may be much more effective for heterolytic cleavage (i.e., more basic) than oxides such as, say, alumina.4... 

How had they arrived at such a conclusion In the mid-1920s, Kirrmann and Prevost both began working on problems posed by Lespieau on reactions of unsaturated hydrocarbons, in particular allylic and conjugated systems. Kirrmann s research topic became focused on bromated aldehydes and the "abnormal" reactions in which, for example, these aldehydes behave as if they were acid bromides, that is,... 

The reaction of unsaturated hydrocarbons with bromine is synthetically important. Unsaturated fatty acids have been electrobrominated in an acetic acid/acetonitrile medium and at platinum electrodes [128]. The mechanism and rate constant for the process with oleic, erucic, and linoleic acid were elucidated. The a-bromination of a,f-unsaturated ketones has been reported [129] on the basis of the electrolysis of a substrate/CF3COOH/CuBr/Et4NOTs/ MeCN reaction system. CuBr is present as a catalyst. 

Benter, Th., M. Liesner, R. N. Schindler, H. Skov, J. Hjorth, and G. Restelli, REMPI-MS and FTIR Study of N02 and Oxirane Formation in the Reactions of Unsaturated Hydrocarbons with NO, Radicals, . /. Phys. Chem., 98, 10492-10496 (1994). 

Alkanes can be activated by both hard and soft transition metal complexes. Hard catalysts have been known for a long time, although examples involving alkanes are few in number, and all are from studies of recent years. Soft catalysts have become important and have been much studied during the past decade and are widely used for reactions of unsaturated hydrocarbons. It was the use of such soft catalysts that Halpem had particularly in mind when he spoke of the development to activate alkanes as an important and challenging problem. 

In acid-catalyzed reactions of unsaturated hydrocarbons (alkenes, alkynes, arenes) positive hydrocarbon ions—carbocations—are formed, which are then responsible for the electrophilic transformations 93b... 

On the basis of the nature of the initiation step, polymerization reactions of unsaturated hydrocarbons can be classified as cationic, anionic, and free-radical polymerization. Ziegler-Natta or coordination polymerization, though, which may be considered as an anionic polymerization, usually is treated separately. The further steps of the polymerization process (propagation, chain transfer, termination) similarly are characteristic of each type of polymerization. Since most unsaturated hydrocarbons capable of polymerization are of the structure of CH2=CHR, vinyl polymerization as a general term is often used. 

This paper presents a new method for preparing 1,2-bis-(dichlorophosphino)alkanes based on the reaction of unsaturated hydrocarbons with PCl and elemental phosphorus at 180-250°C under autogenous pressureI. The basic reaction with ethylene is... 

The third aspect considered will be concerned with an attempt to present our view on the problem of the evolution of supported Pd catalysts in the course of catalytic reactions. Here again, we shall limit our considerations to reactions of unsaturated hydrocarbons, alkanes, and CO with H2. 

In contrast to the reactions of unsaturated hydrocarbons, hydration, hydrogenation and oxidation by molecular oxygen seem to be dissociative rather than molecular. 

The great chemical resistibility of aliphatic hydrocarbons and the aggregate1 state of their members poor in carbon make them appear us unsuitable material for eleotrolytical experiments. Only the addition-reactions of unsaturated hydrocarbons offer an experimental field. This has not yet been developed. These reactions are cathodic in the addition of hydrogen, and anodic in the addition of halogens, etc. The fact that such hydrocarbons occur in the decomposition of aliphatic acids gives us an indication as to their behavior, which will he mentioned at the proper place. 

A major effort to study the chemistry of the zero oxidation state lanthanides on a preparative scale involved their reactivity with neutral unsaturated hydrocarbons 14, 60). This class of reagents was of interest because reactions of unsaturated hydrocarbons with metals constitute such an important component of organometallic chemistry and because species such as alkenes and alkynes were not common as ligands or reactants in organolanthanide chemistry at that time. 

Some interesting stereoselective anodic reactions of unsaturated hydrocarbons have been known, although the stereoselectivity is not always high [367-369]. The reaction seems to proceed via radical cations of the diene. Ando and coworkers [368] investigated in detail the stereochemical consequence of anodic (probably EGA) catalyzed oxygenation of stereoisomeric syn and anti) di-/-butyl(bicyclo[3,3,l]non-9-ylidenes) compared with the stereochemistry of the photosensitized oxygenation. 

Many of the significant reactions of unsaturated hydrocarbons (hydrogenation, isomerization, carbonylation, oxidation, polymerization) are catalyzed heterogeneously by metals in or near Group VIII or homogeneously by salts and complexes of these elements. Those reactions effected in both systems are discussed in terms of probable common intermediates anomalies, where they occur, are ascribed either to the ability of surfaces to form intermediate species which cannot be stabilized by single metal atoms or to the ability of the latter to coordinate simultaneously more than one hydrocarbon molecule. 

Cyclohexane can be dehydrogenated to benzene and also benzene can be hydrogenated to cyclohexane, but these reactions cannot be controlled to give the intermediate olefin and diene. Cyclohexene and cyclohexadiene exhibit the characteristic addition reactions of unsaturated hydrocarbons. Cyclohexatriene, or benzene, shows unexpected properties in that it exhibits saturated properties imder ordinary conditions and gives some of the addition reactions of uhsaturated hydrocarbons with extreme difficulty. 

W. Panyaburapa, T. Nanok,J. Limtrakul, Epoxidation reaction of unsaturated hydrocarbons with H2O2 over defect TS-1 investigated by ONIOM method Formation of active sites and reaction mechanisms, /. Phys. Chem. C 111 (2007) 3433. 

Paterno, E. and Chieffl, G. (1909). Light-induced chemical synthesis. Part 2. Reaction of unsaturated hydrocarbons with aldehydes and ketones. Gazzetta Chimica Italiana, 39, 341-50. 

M. Salmerdn and G.A. Somoijai. Desorption, Decomposition, and Deuterium Exchange Reactions of Unsaturated Hydrocarbons (Ethylene, Acetylene, Propylene, and Butenes) on the Pt(lll) Crystal Face. J. Phys. Chem. 86 341 (1982). 

In the above two examples, oxidative coupling of two olefin molecules occurs. It is likely that the catalysis of numerous cyclooligomerization reactions of unsaturated hydrocarbons proceeds in this manner, as shown for the example of butadiene in Equation 2-54. 

Transition-Metal-Promoted Reactions of Unsaturated Hydrocarbons. IV. Reactions of Norbornenyl Complexes of Palladium(II) with Group V Donor Ligands, Olefins, 1,3-Dienes and 1,2-Dienes, E. Ban, R. P. Hughes, and J. Powell, J. Organometal. Chem., 69, 455 (1974). 

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