Octenes isomerizations

For this specific task, ionic liquids containing allcylaluminiums proved unsuitable, due to their strong isomerization activity [102]. Since, mechanistically, only the linkage of two 1-butene molecules can give rise to the formation of linear octenes, isomerization activity in the solvent inhibits the formation of the desired product. Therefore, slightly acidic chloroaluminate melts that would enable selective nickel catalysis without the addition of alkylaluminiums were developed [104]. It was found that an acidic chloroaluminate ionic liquid buffered with small amounts of weak organic bases provided a solvent that allowed a selective, biphasic reaction with [(H-COD)Ni(hfacac)]. 

Bicyclo[4,2,0]octene isomerizes smoothly to yield 1,3-cyclo-octadiene only at temperatures appreciably higher than are necessary for the mono-cyclic cyclobutenes. A study of this reaction in the gas phase in the temperature range 235 to 285° C yielded the Arrhenius equation... 

H- and C-labeling revealed that the decomposing molecular ions of 1-, 2-, 3-, and 4-octene isomerize to a mixture of interconverting structures within 10 s after ionization. The equilibration of double bond isomers is mainly due to radical-... 

The formation of the parafiSns after the second minute since the first reaction taking place is octene isomerization. 

COT is prepared by the polymerization of ethyne at moderate temperature and pressure in the presence of nickel salts. The molecule is non-planar and behaves as a typical cyclic olefin, having no aromatic properties. It may be catalytically hydrogenated to cyclo-octene, but with Zn and dil. sulphuric acid gives 1,3,6-cyclooclairiene. It reacts with maleic anhydride to give an adduct, m.p. 166 C, derived from the isomeric structure bicyclo-4,2,0-octa-2,4,7-triene(I) ... 

In examination of various disubstituted cyclic olefins, the following decreasing isomerization order was adduced Pd Rh, Ru, Pi > Os > r 84). At 20% conversion of 1-octene to octane, the ratio of isomerization to hydrogenation in isopropanol for various unsupported metals was Pd (2.05), Rh (0.125), Ru (0.121. Pt (0.025), Ir (0.025), Os (0.009) 82). Palladium is used frequently when migration and isomerization are wanted platinum, when they are to be avoided (2J24). 

Because of the difficulty in selling large amounts of C10 and Cl8+ olefins, these were isomerized to internal olefins followed by disproportionation. Here the important internal olefins for the synthesis of LAB are obtained (Fig. 5) [34]. Equations (4) and (5) illustrate the isomerization and disporportionation on 1-octene as an example. 

Hydrosilylation by Ziegler-type catalyst systems [e.g., Ni(acac)2/AlEt3] has been examined for the reaction of 1-octene with EtjSiH in benzene 178). Complications include competing isomerization and reduction to metal however, 1,3-dienes or terminal acetylenes are readily hydrosilylated withRC i CH, the major product is CH2 CR. CRiCHSiXj. 

A catalyst used for the u-regioselective hydroformylation of internal olefins has to combine a set of properties, which include high olefin isomerization activity, see reaction b in Scheme 1 outlined for 4-octene. Thus the olefin migratory insertion step into the rhodium hydride bond must be highly reversible, a feature which is undesired in the hydroformylation of 1-alkenes. Additionally, p-hydride elimination should be favoured over migratory insertion of carbon monoxide of the secondary alkyl rhodium, otherwise Ao-aldehydes are formed (reactions a, c). Then, the fast regioselective terminal hydroformylation of the 1-olefin present in a low equilibrium concentration only, will lead to enhanced formation of n-aldehyde (reaction d) as result of a dynamic kinetic control. 

Chart 1 Ligands used for isomerizing hydroformylation of internal octenes and 2-pentene. 

The ligands synthesized were also apphed to the isomerizing hydroformylation of more reactive 2-pentene. At 120 °C/ 20 bar quantitative conversion of olefin to aldehydes was achieved within 40 min. Trends similar to those described for internal octene hydroformylation were found. The regioselectivity obtained for the individual ligands tends to be 5% higher compared to that for the octenes. Thus, in the presence of 10 75% of n-hexanal were determined, compare Table 3. Obviously, 2-pentene is able to react more smoothly to the terminal isomer compared to olefins having the double bond in an more internal position. Illustrative for this effect are also literature results obtained for 2- and 4-octene.4,5... 

Disubstituted Alkenes. Simple 1,2-disubstituted alkenes such as 2-octene or cyclohexene, which produce only secondary aliphatic carbocation reaction intermediates, do not undergo reduction upon treatment with a Brpnsted acid and an organosilicon hydride. Even when extreme conditions are employed, only traces of reduction products are detected.192 203 207-210,214 An exception is the report that 4-methyl-2-pentene forms 2-methylpentane in 70% yield when heated to 50° for 20 hours with a mixture of Et3SiH/TFA containing a catalytic amount of sulfuric acid. It is believed that 4-methyl-2-pentene is isomerized to 2-methyl-2-pentene prior to reduction.203... 

Bicyclooctanes, isomerization paths of, 20 282 Bicycio (2.2.2)-2- octene, 20 269, 270 Bifimctional catalysts, ring closure, cyclization, 29 311-316 C5 cyclization, 29 311... 

Fig. 3. The thermal isomerization of 1,1-dicyclopropylethylene. (X) axis Time in minutes (Y) axis Percentage yield o 1,1-dicyclopropylethylene 0, 1-cyclopropyl-cyclopentene 0, bicyclo[3,3,0]octene-l.

Frey and Ellis, 1965). The Arrhenius parameters are very close to those obtained for the cia-l-methyl-2-vinylcyclopropane and support the l>ostulated similarity of the two transition states. Further evidence that the low A factor arises mainly from the loss of internal rotations in the transition complex, comes from the work of Grimme (1965) on the thermal isomerization of bicyclo[5,l,0]octene-2 to eyclo-octa-1,4-diene. 

The thermal isomerization of this compound has been studied in both gas and liquid phases (Branton et al., 1965). The compound is more stable than the corresponding bicyclo-octene but does isomerize to... 

Levsen, K. Isomerization of Hydrocarbon Ions. II. Octenes and Isomeric Cycloalkanes. Collisional Activation Study. Org. Mass Spectrom. 1975,10, 55-63. 

When 1-octene was the substrate and the reaction was carried out in CH3CO2D, no D appeared in the mixture of octene isomers. In order to determine whether the 2-octene formed was obtained via a 1,3 shift [Eq. (54)] or two cocurrent 1,2 shifts [Eq. (65)], the isomerization was carried out with 1-octene labeled in the 3 position, C5HuCD2CH=CH2. The 2-octene isolated was not labeled in the methyl group. Hence, Eq. 

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