Alkenes containing polar groups

The direct alkenylation of aromatics tolerates a variety of alkenes. Besides the alkenes mentioned above, lower alkenes (e.g. 1-butene, propene) [6], alkenes containing polar groups (e.g. acrylonitrile) [4b] and cychc alkenes such as cyclooctene [7] all participate in the palladium(II)-promoted substitution of arenes. In most cases, however, the yields of these reactions were prohibitively low (less than 20%). 

Ethylene bis-(tri-o-tolylphosphite)nickel(0) in the presence of HCI is a useful catalyst for the isomerization of alkenes containing polar groups. Hex-5-enal (16), for example, is converted into a mixture of cis- and rm/i -4-hexenal in quantitative yield the isomerization is particularly useful since a,j3-unsaturaled compounds are not produced. 

The availability of the unshared pair of electrons on the heteratcm(s) dictates the potential reactivity of these compounds. For enamines (vinylamines) or ketene aminals, the more basic -NR2 groups give more reactive ccnpounds. Secondly, the orbital containing the available electron pair must be ooplanar with the pi orbital of the alkene for polarization, 4, to occur. Clearly, greater polarization gives more nucleophilic character to the /3-carbon and enchaneed reactivity towards isocyanates. 

Polyolefin - Polyolefins are a large class of carbon-chain elastomeric and thermoplastic polymers usually prepared by addition (co)polymerization of olefins or alkenes such as ethylene. The most important representatives of this class are polyethylene and polypropylene. There are branched and linear polyolefins and some contain polar pendant groups or are halogenated. Unmodified polyolefins are characterized by relatively low thermal stability and a nonporous, nonpolar surface with poor adhesive properties. Processed by extrusion, injection molding, blow molding, and rotational molding. Other thermoplastic processes are used less frequently. This class of plastics is used more and has more applications than any other. Also called olefinic resin, olefinic plastic. 

Ethylene can be copolymerized with alkene compounds or monomers containing polar functional groups, such as vinyl acetate and acrylic acid. Branched ethylene/ alkene copolymers are essentially the same as LDPE, since in commercial practice a certain amount of propylene or hexene is always added to aid in the control of molecular weight. 

Some nonionic collectors such as alkenes can also be used as flotation collector although they do not contain the strong polar groups. It was recently reported that octylphenol polyoxyethylene ether can be used to flotate quartz and cassiterite [26]. The stmcture of octylphenol polyoxyethylene ether can be expressed as follows ... 

Ligand screening experiments were conducted on the alkenes 1-pentene and pent-4-en-l-ol, because such substrates were inert to 3a-3c (15). Pentene lacks any polar or protic group and pentenol contains the alkene and OH separated by 3 carbons. The preliminary studies involved phosphines with both imidazol-2-yl and pyrid-2-yl substituents on P as well as t-Bu, i-Pr, Ph, and Me groups (16). From the screening, complex 1 derived from the phosphine ligand 4 (17) was identified as the most capable (in terms of both reaction rate and final yield) of promoting isomerization of both 1-pentene and pent-4-en-l-ol. 

This group has been best investigated theoretically, and is the most used in large-scale production. The basic members are ethylene and its derivatives. According to the type of substituent, the group contains two subgroups, alkenes (olefins) and polar vinyl monomers. 

When methylene chloride solutions of the alkene and aluminium trichloride were mixed a yellow solid precipitated. The precipitate contained both alkene and aluminium trichloride. Except for the cyano absorption the IR spectrum of the alkene in the precipitate is unchanged. Aluminium trichloride has co-ordinated to the cyano groups but not broken the double bond - a betaine has not been formed. The complex appears to be polymeric, it will not dissolve in polar aprotic solvents. However, it will dissolve in chloroform without chemical reaction if a little methanol is added. Apparently, the polymeric structure is disrupted by methanol co-ordination. The HNMR (in CDC13) spectrum shows that one molecule of alkene dissolves per molecule of alcohol. Despite the proximity of an alcohol molecule to the strongly polarized alkene no chemical reaction takes place in this solvent. 

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