Alkenes, Alkynes, and Polymers

The lUPAC names for alkenes and alkynes are similar to those of alkanes. The lUPAC name of the simplest alkyne is ethyne, although it is often called by the conunon name, acetylene (see Table 17.4). When naming alkenes and alkynes, the longest carbon chain must contain the double or triple bond. 

Examples of naming an alkene and an alkyne are shown in Sample Problem 17.3. 

Write the lUPAC names and formulas for alkenes and alkynes draw the condensed structural formulas for the monomers that form a polymer. 

FIGURE 17.2 Ball-and-stick models of ethene and ethyne show the functional groups of double or triple bonds. 

Analyze the Problem Functional Group Family lUPAC Naming A 

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Electron-deficient carbenium ions interact not only with n-donors but also with other electron-rich compounds, including alkenes, alkynes, and aromatic rings. For example, vinyl monomers and polymer chains may complex carbenium ions. Electrophilic addition (propagation) may proceed by Jl-complexation as in the asymmetric complex (C ) shown in Eq. 14. 

In a series of papers [30-35], Blum and co-workers reported the hydrogenation of alkenes, alkynes, and arenes in the presence of a hydrated ion-pair [0ct3NMe] [RhCl4(H20)n] . The quaternary ammonium tetrachlororhodate also catalyzes HTR of alkynes, alkenes and a,j6-unsaturated carbonyl compounds with polymethylhydrosiloxane [36, 37]. Recently, heterogenized and therefore recyclable quaternary ammonium halometallates, namely glass-encapsulated catalysts [38] and polymer-bound tetrachlororhodate [39], have been described. Both types of the insoluble catalysts effectively promote various processes including the hydrogenation of alkenes and the HTR of a,/9-unsaturated carbonyl compounds [40]. 

For this purpose, nano dispersed palladium 15 was introduced into the composite material locating the Pd next to the polymer-bound ammonium cations. This was achieved after ionic attachment of Pd as palladate followed by reduction to Pd(0) and then pumping a solution of borohydride or hydrazine through the reactor (Scheme 12). Besides benzyl ether cleavage transfer hydrogenations were utilized for the reduction of alkenes, alkynes, and aromatic nitro groups (Scheme 13). 

Palladium chemistry with alkene, alkyne, and enyl ligands has deep implications for palladium-catalyzed organic syntheses and in polymer chemistry. The importance of these catalytic reactions is enormous, and new developments... 

Intermolecular-enyne metathesis, if it is possible, is very unique because the double bond of the alkene is cleaved and each alkylidene part is then introduced onto each alkyne carbon, respectively, as shown in Scheme 9. If metathesis is carried out between alkene and alkyne, many olefins, dienes and polymers would be produced, because intermolecular enyne metathesis includes alkene metathesis, alkyne metathesis and enyne metathesis. The reaction course for intermolecular enyne metathesis between a symmetrical alkyne and an unsym-metrical alkene is shown in Scheme 9. The reaction course is very complicated, and it seems impossible to develop this reaction in synthetic organic chemistry. 

The Pauson-Khand reaction involves the aimulation of an alkene, an alkyne and carhon monoxide to yield cyclopentenones. Recently, it was shown that in this respect polymer-hound species (60) is an effective catalyst which may be generated by heating Co2(CO)g with polystyrene-bound phosphine (Scheme 4.37) [129]. 

An excellent method for the synthesis of 1,3-diene from polymer-supported alkyne and olefin (Scheme 16) has also been reported. Reaction of polymer-supported alkyne 44 and alkene 47a in the presence of Ic gives polymer-supported 1,3-diene 45a, which is treated with a palladium catalyst in the presence of a nucleophile for cleavage from the polymer to give 46a in 66% yield. In a similar manner, 46b, 46c, and 46d are obtained from polymer-supported alkyne 44 in high yields. These results indicate that various kinds of nucleophiles are introduced at the diene allylic position corresponding to the propargylic position in 44 (Scheme 16). 

Silicon vapor reacts with alkanes, alkenes, alkynes, arenes, ketones, alkyl halides, and ethers to give mainly polymers (104). 

Several groups have employed N-halosuccinimdes for the halofluorination of alkenes. Laurent and co-workers have found that triethylamine tris(hydrofluoride) is a suitable fluoride source for the halofluorination of a number of alkenes (Scheme 70).137 Other examples of halofluorinations include NBS and tetrabutylammonium fluoride as the halogen sources for the formal addition of BrF across funtionalized cyclohexenes138 and the halofluorination of alkenes and alkynes by all three N-halosuccinimides and polymer-supported HF.139... 

The Oishi-Prausnitz modification, UNIFAC-FV, is currently the most accurate method available to predict solvent activities in polymers. Required for the Oishi-Prausnitz method are the densities of the pure solvent and pure polymer at the temperature of the mixture and the structure of the solvent and polymer. Molecules that can be constructed from the groups available in the UNIFAC method can be treated. At the present, groups are available to construct alkanes, alkenes, alkynes, aromatics, water, alcohols, ketones, aldehydes, esters, ethers, amines, carboxylic acids, chlorinated compounds, brominated compounds, and a few other groups for specific molecules. However, the Oishi-Prausnitz method has been tested only for the simplest of these structures, and these groups should be used with care. The procedure is described in more detail in Procedure 3C of this Handbook. 

Both intermolecular and intramolecular additions of carbon radicals to alkenes and alkynes continue to be a widely investigated method for carbon-carbon bond formation and has been the subject of a number of review articles. In particular, the inter- and intra-molecular additions of vinyl, heteroatomic and metal-centred radicals to alkynes have been reported and also the factors which influence the addition reactions of carbon radicals to unsaturated carbon-carbon bonds. The stereochemical outcome of such additions continues to attract interest. The generation and use of alkoxy radicals in both asymmetric cyclizations and skeletal rearrangements has been reviewed and the use of fi ee radical reactions in the stereoselective synthesis of a-amino acid derivatives has appeared in two reports." The stereochemical features and synthetic potential of the [1,2]-Wittig rearrangement has also been reviewed. In addition, a review of some recent applications of free radical chain reactions in organic and polymer synthesis has appeared. The effect of solvent upon the reactions of neutral fi ee radicals has also recently been reviewed. ... 

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