Olefins and their Reaction Products

The combination of olefins with acids to form esters, etc., is strikingly similar to the combination of ammonia and acids to form salts. In the great majority of these compounds one molecule of the olefin or ammonia combines with one equivalent of the acid. The reaction is also reversible in both series. Designating the olefin by the symbol En, (ethylene as example), the following reactions may be given. 

So-called anomalous olefinates, which contain a different proportion of acid or salt than the 1 1 ratio are also known. The zinc chloride compound just given is an example partially saturated polyolefins, such as the mono- 

Mixed addition compounds containing olefins have also been described for example, FeCl2.C2H4.H2O [J. Kachler, Ber. 2, 510 (1869)] FeBr2.C2H4.H2O [C. Chojnacki, Z.f. Chem. 1870 p. 419)] (CH3)20.NH3, an olefinate and am-moniate of water, etc. 

These reactions show the similarity between the olefins and ammonia, and that the common property of unsaturation in both leads to the formation of analogous products. 

The simplest compounds which are formed from the olefins are the alkyl halides, which correspond to the ammonium halides. There is at present no direct experimental evidence of the action of catalysts in their formation, but in their dissociation into olefin and hydrogen halide, aluminium chloride, zinc chloride, etc., affect the rate of reaction greatly [P. Sabatier and A. Maihle, C.r. 138, 407 (1904) 238 (1905)]. This shows itself more particu- 

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Depending on the solvent used, the reaction often does not stop (or is not stopped by intention) at the diazoalkane stage, but goes on to carbenes or to carbocations. Carbenes and their reaction products (olefins) are formed in apolar systems, carbocations and subsequently, their stable products in protic solvents (2-38). 

Typical procedure The mole ratio of alkene t-BuOOH catalyst was 10 10 0.25 and 40 mmol of the olefin serving as its own solvent. Thus, 10 mmol of TBHP (80% in di-tert-butyl peroxide) and 0.25 mmol of vanadium pentoxide were added to 50 mmol of the olefin and the reaction mixture was stirred at 60°C under a dinitrogen atmosphere. The products formed were analyzed by GC by comparison of their retention time with those of authentic samples. Good yields of epoxides were obtained only with an excess of olefin to TBHP of 5 1. That the olefin doubles up as the solvent makes for a more practical procedure. Typical results (34) are shown in Table 1 ... 

The estimation method described above has the following additional advantages the products used are determined by analysis of only one phase in our experiments, and their relative magnitudes should be reasonably accurate and, they are all alpha-olefins, and secondary reactions involving these products should be no faster than the reactant decomposition rate. Therefore, at low conversions (< 10%), secondary reactions can be neglected. 

Diazirines were detected when there was broad activity in the carbene field. From their structure, cleavage to nitrogen and carbene was foreseeable, and this was shown to occur on photolysis as well as on thermolysis. As early as 1962, Frey and Stevens in a series of papers reported on photolysis of simple diazirines. According to these authors, diazirines are especially fit for the study of excited intermediates and their stabilization products. Products of isomerization of carbenes, i.e., olefins and cyclopropanes, are formed containing more energy than is necessary for their further decomposition. Their stabilization by loss of energy to partners competes with stabilization by subsequent reactions. 

The olefination reaction leads to a mixture of alkenes (56) and (57) which on heating forms (58) and (59). Both the Wittig reaction and the Homer-Wittig have been used in the synthesis of leukotrienes and their metabolic products, for example 12-(S)-hydroxyeicosatetraenoic acid... 

Ziegler-Natta catalysts are very sensitive to moisture, oxygen, and peroxides. As solvents for polymerization reactions, any compounds may be used provided they do not react with the catalysts and they do not cause their decomposition. For practical application, paraffins, cycloparaffins, and aromatic hydrocarbons are utilized. The choice of solvent depends on reaction conditions and the catalyst, on its availability in sufficient quantities, and on its sufficient purity. Usually, pressure from 0.1 to 3 MPa is utilized. Often, the concentration of monomers is low in the case of reactive olefins however, their polymerization is sometimes carried out utilizing the excess of the olefin as a solvent (only small amounts of alkanes are present and are used to introduce the catalyst). The temperature of the process varies from 170 to 470 K depending on utilized catalysts, the olefin, and the desired product. 

The effect of free hydroxyl groups in proximity to reactive olefins and their effects on olefin metathesis reactions has been an area of ongoing study [25]. For example, the use of alcohol additives, particularly phenols, to improve catalyst activities and hfetimes in olefin metathesis has been reported by Meyer and coworkers [26]. Their study evaluated the use of phenol as an additive in selfmetathesis, ethenolysis, and CM reactions. When the CM of styrene with terminal olefins 37 and 38 was investigated using Ru-based catalyst 1, the conversions were typically low (< 50%) (Scheme 12.13). Upon the addition ofphenol as an additive,a significant improvement in the conversion of the CM reactions was observed, and olefins 40 and 41 were obtained in 76% and 65% conversion, respectively. Similarly, a CM reaction between 3,3-dimethylbutene and 1-undecene showed none of the desired CM until phenol was added, whereby cross product 42 was observed in 57% conversion. 

Pioneering studies by Emmet suggested in 1953 that ethylene acts as a chain initiator in Fe-catalyzed Fischer-Tropsch reactions. Many authors have used isotopi-cally labeled olefins to confirm that 1-alkenes are the primary reaction products (although they are thermodynamically instable under the reaction conditions). For instance, Somorjai s group has shown, using a polycrystalline iron sheet (1 cm ), that the addition of ethylene or propene in the syn gas increases the length of the polymer chain. These olefins readsorb and readily form polymers by insertion into adsorbed C fragments. Thus, the Fischer-Tropsch mechanism involves two steps, namelly the formation of olefins and their polymerization ... 

The hydroformylation reaction is carried out in the Hquid phase using a metal carbonyl catalyst such as HCo(CO)4 (36), HCo(CO)2[P( -C4H2)] (37), or HRh(CO)2[P(CgH3)2]2 (38,39). The phosphine-substituted rhodium compound is the catalyst of choice for new commercial plants that can operate at 353—383 K and 0.7—2 MPa (7—20 atm) (39). The differences among the catalysts are found in their intrinsic activity, their selectivity to straight-chain product, their abiHty to isomerize the olefin feedstock and hydrogenate the product aldehyde to alcohol, and the ease with which they are separated from the reaction medium (36). 

The initial products of beta-scission are an olefin and a new carbenium ion (Equation 4-9). The newly-formed carbenium ion will then continue a series of chain reactions. Small ions (four-carbon or five-carbon) can transfer the positive charge to a big molecule, and the big molecule can crack. Cracking does not eliminate the positive charge it stays until two ions collide. The smaller ions are more stable and will not crack, They survive until they transfer their charge to a big molecule,... 

Since electron-donating substituents at the phosphorus atom favor addition reactions over olefination reactions, addition of 9 to aldehydes leads to the exclusive formation of the silyl-pro-tected allylic alcohols 10. No reaction products arising from Wittig alkenylation could be detected. The ylides (R,S)-9 and (S.S)-9 and their enantiomers were prepared from the corresponding optically pure l-[2-(diphenylphosphino)ferrocenyl]-A,A -dimethylethanamine diastereomers 7 via the phosphonium salts 8. 

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