Olefin also hydrogenation

Hydrofluorocarbons are also prepared from acetylene or olefins and hydrogen fluoride (3), or from chlorocarbons and anhydrous hydrogen fluoride in the presence of various catalysts (3,15). A commercial synthesis of 1,1-difluoroethane, a CFG alternative and an intermediate to vinyl fluoride, is conducted in the vapor phase over an aluminum fluoride catalyst. 

Chemical Properties. Higher a-olefins are exceedingly reactive because their double bond provides the reactive site for catalytic activation as well as numerous radical and ionic reactions. These olefins also participate in additional reactions, such as oxidations, hydrogenation, double-bond isomerization, complex formation with transition-metal derivatives, polymerization, and copolymerization with other olefins in the presence of Ziegler-Natta, metallocene, and cationic catalysts. All olefins readily form peroxides by exposure to air. 

Amiridis followed that also in propene hydrogenation over Pt-Au/Ti02 a minimum ensemble of Pt atoms is necessary for a successful concomitant adsorption of olefin and hydrogen. However, beside this dilution effect of gold on the bimetallic particles, an electronic impact can not be excluded. An application of Amiridis ... 

The addition of a cation to an olefin to produce a carbonium ion or ion pair need not end there but may go through many cycles of olefin addition before the chain is eventually terminated by neutralization of the end carbonium ion. Simple addition to the double bond is essentially the same reaction stopped at the end of the first cycle. The addition of mineral acids to produce alkyl halides or sulfates, for example, may be prolonged into a polymerization reaction. However, simple addition or dimerization is the usual result with olefins and hydrogen acids. The polymerization which occurs with a-methyl-styrene and sulfuric acid or styrene and hydrochloric acid at low temperatures in polar solvents is exceptional.291 Polymerization may also be initiated by a carbonium ion formed by the dissociation of an alkyl halide as in the reaction of octyl vinyl ether with trityl chloride in ionizing solvents.292... 

The various modes of bonding that have been observed for alkenes to the trinuclear osmium clusters are shown in Fig. 7 [see (88)]. The simple 77-bonded structure (a) is relatively unstable and readily converts to (c) the vinyl intermediate (b) is obtained by interaction of alkene with H2Os3(CO)10 and also readily converts to (c) on warming. Direct reaction of ethylene with Os3(CO)12 produces (c), which is considered to be formed via the sequence (a) — (b) — (c) and (d). Both isomers (c) and (d) are observed and involve metal-hydrogen and metal-carbon bond formation at the expense of carbon-hydrogen bonds. In the reaction of Os3(CO)12 with C2H4, the complex 112088(00)902112, (c), is formed in preference to (d). Acyclic internal olefins also react with the carbonyl, with isomerization, to yield a structure related to (c). Structure (c) is... 

Variation of the olefin also has an effect on kaaa//cab3. For example, the irradiation of benzophenone in 1-methylcyclohexene gives a moderate yield of the oxetane (even though there are three more allylic hydrogens on this olefin as compared to cyclohexene). Isobutylene too gives much higher yields of the oxetane than 1-butene.37,66 The controlling factor in these cases may be the increased stability of the diradical intermediates. 

Reforming reactions comprise dehydro-/hydrogenations and olefins might also be intermediates of other reactions—such as the above-mentioned exchange reactions. The two forms of associatively adsorbed olefins have been already mentioned n complexes and afl two-cr-bonded complexes. The questions posed are as follows (a) Do dissociative forms of olefins also exist (b) are any of these forms reactive enough to be an intermediate of hydrogenation/dehydrogenation reactions ... 

The iridium complexes used as precatalysts are air-stable and easy to handle. A further attractive feature is the modular nature of the HetPHOX chiral ligands, which makes it possible to tailor the catalyst structure for a specific substrate. Unfunctionalized and functionalized olefins were hydrogenated with good to excellent enantioselectivity using these iridium complexes and it was possible to obtain also high yield and good enantioselectivity (99% yield, 72% ee.) in the hydrogenation of ( )-phenyl-(l-phenylethylidene)-amine. ... 

It was also shown that the ratio of oxidized alcohol to oxidized Fe2+ could be greater then one. Baxendale and Wilson (1957) showed that hydroxyl radical initiating the chain polymerization of olefins by hydrogen peroxide was the same process as the rapid oxidation of glycolic acid. Merz and Waters (1947) confirmed that simple water-soluble alcohols are oxidized rapidly by Fenton s reagent. The primary alcohols are oxidized to aldehydes, which are further oxidized at comparable rates by exactly the same mechanism. Merz and Waters proposed a mechanism of chain oxidation of alcohols and aldehydes by sodium persulfate, hydrogen peroxide, and an excess of ferrous salt as follows ... 

Although the mechanism of the platinum-catalyzed hydrosilation is poorly understood, it seems probable that an intermediate with a platinum-silicon bond is formed, with which the olefin and hydrogen may also be complexed. The cleavage of pentamethyldisilane may be rationalized by considering nucleophilic attack of isopropyl alcohol, which is used for preparing the catalyst solution, on the silicon atom that has become attached to platinum and thus vulnerable to the attack by any Lewis base (see also Section IV, A, 2,f B, 2,b). 

The efficiency of conjugated dehydrogenation of olefins with hydrogen peroxide was also confirmed in studies of propylene dehydrogenation to allene [60], The well-known process of propylene oxidative dehydrogenation to allene in the presence of iodine [61] at 625-700 °C gives low yields of the target product (3.6% allene) at low selectivity of the process (6%). 

In the normal oxo reaction a certain amount of hydrogenation occurs, a minor amount of olefins being converted to paraffins in the case of certain olefinic compounds hydrogenation indeed occurs to the exclusion of hydroformylation. It is a remarkable fact that this catalytic reaction occurs in the presence of carbon monoxide and also of sulfur compounds, although cobalt metal is notoriously poisoned by traces of these compounds. The significance of this was pointed out by Adkins and Krsek (23) and Wender, Orchin, and Storch (25) in terms of the concept that the hydroformylation catalyst is a homogeneous one, not sensitive to carbon monoxide or sulfur compounds and in this respect different from usual solid cobalt catalysts. 

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