Halogenation, of unsaturated hydrocarbons

Winterton, N. Seddon, K. R. Patell, Y. Halogenation of unsaturated hydrocarbons in ionic liquids, World Patent WO 0037400 (2000). 

Halogenation of unsaturated hydrocarbons involves addition of halogen atoms. For example,... 

The great chemical resistibility of aliphatic hydrocarbons and the aggregate1 state of their members poor in carbon make them appear us unsuitable material for eleotrolytical experiments. Only the addition-reactions of unsaturated hydrocarbons offer an experimental field. This has not yet been developed. These reactions are cathodic in the addition of hydrogen, and anodic in the addition of halogens, etc. The fact that such hydrocarbons occur in the decomposition of aliphatic acids gives us an indication as to their behavior, which will he mentioned at the proper place. 

Table XCIL Dipole Moments of Halogen Derivatives of Unsaturated Hydrocarbons D)...

Halogenation of saturated hydrocarbon polymers can hardly be controlled and is frequently assodated with chain degradation phenomena In contrast, the presence of randomly distributed olefinic unsaturations, allows selective halogenation reactions by adopting appropriate conditions. For instance, butyl rubber can be chiorinated or brominated in allylic positions and chloro-butyl or bromo-butyl rubber results The latter polymers are very interesting since they exhibit fast curing rates when sulfur and ZnO are introduced in the formulations. 

The stereodefined alkenyl halides are of prime importance due to the developments of di- or trisubstituted alkene synthesis by cross-coupling reactions between organometallics and alkenyl halides, catalyzed by transition metal compounds [1-4]. 1-Halo-l-alkenes are conveniently synthesized via hydrobo-ration-halogenation reaction [5]. However, with these methods it is not possible to synthesize 2-halo-1-alkenes. Although the halometalation reaction is considered to be a powerful tool for the synthesis of 2-halo-1-alkenes, the reaction has not been adequately developed for such purpose [6]. Lappert and coworkers [7-10] are perhaps the first to report the systematic haloboration reactions of unsaturated hydrocarbons with BX,. However, there is no systematic approach to the haloboration with B-X-9-BBN to organic synthesis [11]. The desired B-X-9-BBN is prepared [12] by the reaction of 9-BBN with phosphorous pentachlo-ride, bromine, or HI. Alternatively, B-X-9-BBN are very conveniently obtained... 

Alkyl The general name for a radical of an alkane an alkyl halide is a halogenated hydrocarbon whose hydrocarbon backbone originated from an alkane. Aligmes An analogous series of unsaturated hydrocarbons with the general fomiula C H2 .2 the alkynes all contain just one triple bond between carbon atoms. 

In connection with the identification of unsaturated hydrocarbons, valuable data are furnished by titration with bromine the bromine addition products may often be used for melting-point or boiling-point determinations. Among the terpenes, the addition products formed with bromine, halogen acid (usually HCb, and nitrosylchloride are of considerable value. The latter derivatives react with organic amines to yield nitrosylamines. (Cf. Rosenthaler, pages 22-28.)... 

In presence of unsaturated hydrocarbons, chain reaction can be generated by halogen radical. This process is termed as photo halogenation. 

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers. 

Such a molecule, containing alternating single and double bonds, would be expected to be quite reactive. Actually, benzene is quite unreactive, and its chemical properties resemble those of the alkanes much more than those of the unsaturated hydrocarbons. For example, the characteristic reaction of benzene with halogens resembles that of the reaction of the alkanes ... 

The unsaturated open-chain hydrocarbons include the alkene or olefin series, the diene series, and the alkyne series. The alkene series is made up of chain hydrocarbons in which a double bond exists between two carbon atoms. The general formula for the series is CnH2n, where n is the number of carbon atoms. As in the paraffin series, the lower members are gases, intermediate compounds are liquids, and the higher members of the series are solids. The alkene series compounds are more active chemically than the saturated compounds. They react easily with substances such as halogens by adding atoms at the double bonds. 

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