Styrene Friedel-Crafts reaction

Alkenyl halides such as vinyl chloride (H2C=CHC1) do not form carbocations on treatment with aluminum chloride and so cannot be used m Friedel-Crafts reactions Thus the industrial preparation of styrene from benzene and ethylene does not involve vinyl chloride but proceeds by way of ethylbenzene... 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Under Lewis-acid-catalyzed conditions, electron-rich arenes can be added to alkenes to generate Friedel-Crafts reaction products. This subject will be discussed in detail in Chapter 7, on aromatic compounds. However, it is interesting to note that direct arylation of styrene with benzene in aqueous CF3CO2H containing H2PtCl6 yielded 30-5% zram-PhCH CHR via the intermediate PhPt(H20)Cl4.157 Hydropheny-lation of olefins can be catalyzed by an Ir(III) complex.158... 

The opposite of the stabilisation of an ester is its activation. If we include in the concept ester the alkyl halides, their Friedel-Crafts reactions provide familiar examples of this phenomenon. An unusual example especially relevant to our present considerations is provided by some results made available to me in advance of publication by Giusti and Andruzzi. Their results [38] on the polymerisation of styrene by iodine and hydrogen iodide can be interpreted in terms of an organic iodide derived from styrene, probably 1-phenylethyl iodide, being activated by the co-ordination of one or two molecules of iodine. This process appears to polarise the C—I bond to such an extent that the normally stable ester becomes activated to a chain-propagating species and induces a pseudocationic polymerisation ... 

Acrylonitrile is obtained from propylene and ammonia. 1,3-Butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking. An overview on the issues of the production of butadiene is given in the literature (5). Styrene monomer is made by the dehydrogenation of ethylbenzene, which is obtained by the Friedel-Crafts reaction of ethylene and benzene. 

Various Brpnsted and Lewis acids can also be used in cationic polymerization of styrene.118 138 159 The molecular weight, however, is difficult to control. Of the usual transfer processes, transfer to the monomer is the most significant reaction. An additional difficulty, the occurrence of Friedel-Crafts reactions, arises if polymerization is carried out in aromatic solvents. As a result, cationic polymerization of styrene usually leads to ill-defined products and is mainly of academic interest.159... 

Styrene (phenylethene, 10) is an important industrial chemical that is prepared by dehydrogenation of ethylbenzene at 600 °C over zinc oxide or chromium(III) oxide on alumina (Scheme 3.7). Ethylbenzene can be produced from benzene and ethene by a Friedel-Crafts reaction. 

Topchiev has reported obtaining a 1,6 polymerization with styrene, resulting in a polymer with structure II. Catalysts used included AICI3-VOCI3 (41). It has been suggested that the product is not II, but rather a crosslinked self-alkylation product brought about by Friedel-Crafts reaction (12). 

Oxoalkylbismuthonium salts react with a sodium salt of dibenzoylmethane to alkylate the active methylene carbon [304]. Treatment of a mixture of Ph3BiF2 and allyltrimethylsilane with lii, -O Hl, in the presence of excess electron-rich arenes yields allylated arenes via the Friedel-Crafts reaction (Scheme 14.149) [305]. The action of tBuOK on a mixture of alkenylbismuthonium salt and styrenes gives al-kylidenecyclopropanes in high yield (Scheme 14.150) [306]. Michael addition of sodium p-toluenesulfinate to a 1-hexynylbismuthonium salt results in the formation of 3-methyl-l-tosylcyclopentene [307]. 

M. Negre, M. Bartholin and A. Guyot, Autocross-linked isoporous polystyrene resins, Angew. Makromol. Chem., 1979, 80, 19-30 J. Hradil and E. Kralova, Styrene-divinylbenzene copolymers post-cross-linked with tetrachloromethane, Polym., 1998, 39, 6041-6048 S. Belfer and R. Glozman, Anion exchange resins prepared from polystyrene cross-linked via a Friedel-Craft reaction, J. Appl. Polym. Sci., 1979, 24, 2147-2157. 

An aqueous Friedel-Crafts reaction has also been used in polymer synthesis. The acid-catalyzed polymerization of benzylic alcohol and fluoride functionality in monomeric and polymeric fluorenes was investigated in both organic and aqueous reaction media. Polymeric products are consistent with the generation of benzylic cations that participate in electrophilic aromatic substitution reactions. Similar reactions occurred in a water-insoluble Kraft pine lignin by treatment with aqueous acid. A Bisphenol A-type epoxy resin is readily emulsified in aqueous medium with an ethylene oxide adduct to a Friedel-Crafts reaction product of styrene and 4-(4-cumyl)phenol as emulsifier.Electrophilic substitution reaction of indoles with various aldehydes and ketones proceeded smoothly in water using the hexamethylenetetramine-bromine complex to afford the corresponding Z A(indolyl)methanes in excellent yields.InFs-catalyzed electrophilic substitution reactions of indoles with aldehydes and ketones are carried out in water.Enzymatic Friedel-Crafts-type electrophilic substitution reactions have been reported. ... 

The cationic polymerization of styrene has been known since the 1960s using Lewis acids or strong protic acids as initiators leading to fast, uncontrolled polymerization due to extensive proton transfer reactions to, for example, counteranion, solvent, monomer, or polymer. In addition, chain transfer occurs as a result of an intramolecular Friedel-Craft reaction of the carbocation with the penultimate monomer unit, resulting in an indane chain end and the release of a proton that can reinitiate a new polymer chain as illustrated in Scheme 8.13. 

Ando et al. [62, 63] suggested using unreacted double bonds in swollen styrene-DVB copolymers, which also react with aromatic rings via Friedel-Crafts reaction forming rigid crosslinks ... 

Spectrum. On the other hand, this band is revealed in the spectrum of the styrene-0.6% DVB copolymer intensively crosslinked with 1 mol of MODE, which contains a comparable amount (1%) of pending chlorine. It is quite possible that industrial MN-200 contains chlorine of a different kind. A part of rather inert chlorine in the form of chloroethyl groups may have originated by the involvement of EDO into the Friedel—Crafts reaction. One may also assume that the initial copolymer of that product incorporates more DVB thus the unreacted pendent double bonds may have interacted with MCDE during the post-crosslinking reaction, leading to the formation of methyl chloropropyl ether fragments [105] ... 

Other types of hypercrosslinked sorbents, namely commercial Lewatit EP63, laboratory samples obtained by post-crosslinking styrene-DVB copolymer with CCI4 [55], by self-crosslinking macroporous copolymer of vinylbenzyl chloride with 20% DVB via Friedel-Crafts reaction [56], or by bridging preliminary chloromethylated macroporous styrene-DVB copolymer [57, 58], are all superior to XAD-2, XAD-4, and activated carbon Ambersorb XE340 with respect to phenol and nitrophenol removal. Material [20%-VBC(F.C.)] retains 2,4-dichlorophenol much stronger than unsubstituted phenol, and, therefore, the presence of phenol in the solution does not impact the retention of the chlorinated phenol. On the contrary, the sorption of phenol from the binary solution depends heavily on the concentration of 2,4-dichlorophenol. 

Styrene is produced in the U.S. from benzene and ethylene by a Friedel-Craft reaction that is followed by dehydrogenation over alumina at600 °C. Polystyrene was first prepared in 1839, though the material was confused for an oxidation product of the styrene monomer. Today, polystyrene is produced in very large quantities and much is known about this material. 

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