Cis-Pent-2-ene

Infrared spectral studies have shown that cis- and tram-olefins are not isomerized by coordination to, or displacement from, platinum salts 127). ras-4-Methylpent-2-ene forms a more stable complex than do trans-4-methylpent-2-ene or cis-pent-2-ene it is suggested 132) that the electron-donating nature of the methyl group is responsible for the latter result by strengthening the v-component of the metal-olefin bond. 

Fig. 20. Percentage yields of trans- and cis-pent-2-ene observed in the reaction of pent-1-ene with hydrogen over palladium—charcoal in methanol (o, ), glacial acetic acid ( , ) and benzene (A,A) solution [145],...

CIS-Pent-2-ene [627-20-3] M 70.1, b 37.1 , d 0.657, n 1.3798. Dried with sodium wire and fractionally distd, or purified by azeotropic distn with MeOH, followed by washing out the MeOH with water, drying and distilling. Also purified by chromatography through silica gel and alumina [Klassen and Ross J Phys Chem 91 3668 1987],... 

Fig. 6.5 Metathesis of cis-pent-2-ene catalyzed by [W]=CHCMe3 (1 in Ch. 3). Plot of the trans/cis ratio of the product but-2-ene versus the yield of but-2-ene. cis-Pent-2-ene/W molar ratio = 500/1 in chlorobenzene at 25°C (Couturier 1992).

Stereochemical aspects of the Birch reduction of cyclopropanes have been examined in a variety of systems. Lithium-ammonia reduction of vinylcyclopropane gives a mixture of pentenes in which cis-pent-2-ene predominates, the products being stable to the reaction conditions. Results in the sodium-ammonia reduction, however, are variable due to equilibration of the pentenes under the reaction conditions, and frans-pent-2-ene is the eventual major product. It was suggested that cis-stereo-selectivity is a characteristic of solvent-separated ion-pair transition states. ... 

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