2-Ethyl-l-pentene

How many monobromination products can be formed by NBS bromination of 2-ethyl-l-pentene Include double-bond isomers. 

When the enantiomerically enriched alkene (5)-3-methyl-l-hexene is employed, 3-ethyl-l-hexanal is formed with 70% retention of configuration together with 4-methyl-l-heptanal and 2,3-dimethyl-l-hexanal, in spite of the fact that the precursor of this product should be achiral 2-ethyl-l-pentene generated through isomerization of (5)-3-methyl-l-hexene. In order to accommodate this result, a 1,2-hydrogen shift mechanism has been proposed that does not include a true cr carbon-Co bond and is faster than the dissociation of olefin from the olefin-Co complex, which appears to be generally accepted. 

Another difference between the two mechanisms is that the former involves 1,2 and the latter 1,3 shifts. The isomerization of 1-butene by rhodium(I) is an example of a reaction that takes place by the metal hydride mechanism, while an example of the TT-allyl complex mechanism is found in the Fe3(CO)i2 catalyzed isomerization of 3-ethyl-l-pentene. " A palladium acetate or palladium complex catalyst was used to convert alkynones RCOCSCCH2CH2R to 2,4-alkadien-l-ones RCOCH= CHCH = CHCHR. ... 

Scheme 90 Cathodic addition of ethyl bromide to 2-methyl-l -penten-3-one.

Effect noted experimentally, but data insufficient to quantitate. r Includes measurements on propylene through 1-hexene, 2-ethyl-l-butene, and 2,4,4-trimethyl-l-pentene. 

Compound A must therefore be 2-bromo-3-ethylpentane. Dehydrobromination of A will follow Zaitsev s rule, so that the major alkene (compound B) is 3-ethyl-2-pentene and the minor alkene (compound C) is 3-ethyl-l-pentene. 

Bromo-3-methylpentane 3-Methyl-2-pentene 2-Ethyl-l-butene... 

SYNS 1,3-BUTADIENE, 2-ETHYL- 2-ETHYL-l,3-BUTADIENE 1-PENTENE, 3-METHYLENE-... 

C8H16 trans-3-octene 14919-01-8 163.15 16.678 2 14975 C8H16 3-methyl-3-ethyl-l-pentene 6196-60-7 180.08 7.782 2... 

The enthalpy of formation of the 2-ethylbutadiene is taken from Reference 8. The enthalpy of formation of the monoolefin products, 3-methyl-l-pentene and 2-ethyl-l-butene, are derived from Reference 11. 

Phillips Pure Grade 1-hexene was redistilled from potassium and contained 0.5% 2-ethyl-1-butene and 0.1% 2-methyl-l-pentene. Percolation through alumina into the saturator had no effect upon rates. 

Several non-polymerizable olefins have been successfully co-polymerized with ethylene, the most successful results being achieved with the r -Cp-amido catalysts. Relevant cases are those of isobutene,260 2-methyl-l-pentene,593 and 2-butene. Typical C2- and ( -symmetric metallocenes like 29 and 32 have been reported to selectively co-polymerize ethylene with as- and /ra r-2-butene, respectively. Working at low ethylene concentration, up to 25% and 14% mol of butene could be incorporated into the co-polymers obtained with 29 and 32, respectively. Independent of the symmetry of the catalyst, the inserted 2-butene units undergo chain-isomerization reactions that lead to isolated methyl groups in the case of trans-2-butene co-polymerization, and to mainly isolated ethyl groups and a minor amount of isolated methyl groups in the case of nr-2-butene insertion, as shown in Scheme 24.594,595... 

The Fe3(CO)i2-catalyzed isomerization of 3-ethyl-l-pentene-3di gives 3-ethyl-2-pentene in which the deuterim label is randomly scrambled among the three methyl groups without loss of deuterium . The recovered 1-olefin also shows rapid random scrambling. These experiments demonstrate the intermediacy of w-allyl iron carbonyl hydrides and indicate Aat multiple addition-eliminations proceed before decomplexation of the catalyst occurs as... 

Fig. 2. Reactions between /-BuCl/Et2AlCl and 3-ethyl-l-pentene (Model for 1,2-unsaturations inPBd)...

The reactivity of growing polystyrene cations toward 1,2-units in polybutadiene has been studied by treating 3-ethyl-l-pentene with the l-chloro-l-(4-methylphenyl)-ethane/Et2AlCl system. Addition of Et2AlCl to l-chloro-l-(4-methylphenyl)ethane gives rise to an ion pair which simulates the growing polystyrene carbocation. 

Similar unsatisfactory results, usually with even lower inductions are obtained with other terminal aliphatic alkenes such as 1-pentene, 2-methy]-l -butene, 3-methyl-l -butene, 2,3-dimethyl-l-butene, 3,3-dimethyl-l-butene, 2,3,3-trimethyl-l-butene, 2-ethyl-l-hexene, I-hex-ene and 1-octene (Table 1). 

With alkynes hydrocarbonylative coupling leads to unsaturated ketones with exclusive cis addition of hydrogen and the acyl group. Thus, rhodium carbonyl catalyzed carbonylation of acetylenes and ethene with carbon monoxide and hydrogen stereospecifically leads to a./l-un-saturated ethyl ketones by cross hydrocarbonylation4- 5, e.g., diphenylacetylene with ethene in the presence of Rh4(CO)l3 gives ( )-1.2-diphenyl-l-penten-3-one in 91 % yield5. 

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