Alkylation of styrenes

Metalation of carboxylic acids, Carboxylic acids are converted to sodium a-sodiocarboxylates by this anion radical in combination with diethylamine or, preferably, TMED A. The anions prepared in this way have been used for alkylation of styrene and dienes. 

Other o-nitrophenol-containing resins have been prepared with the aim of increasing the distance between the reactive center and the macromolecular backbone, which should accelerate the active ester formation by achieving an easier approach of the reagents. Thus, the Friedel-Crafts alkylation of styrene-divinyl-benzene copolymer with 4-hydroxy-3-nitrobenzyl chloride promoted by aluminium trichloride gave 4-hydroxy-3-nitrobenzylated polystyrene (70) (approximately 30% of the aromatic rings of the polymer were substituted according to elemental... 

Reductive alkylation of styrenes. Using a sacrificing aluminum anode, the electrochemical reductive alkylation of styrenes with alkyl halides in DMF (60°) takes place at the P-carbon. If proper a,(0-dihaloalkanes are used as the alkylating agents, arylcycloalkanes are formed. 

The EB present in recovered mixed xylenes is largely converted to xylenes or benzene. The EB used to make styrene is predominately manufactured by the alkylation of benzene with ethylene. 

Friedel-Crafts alkylation using alkenes has important industrial appHcations. The ethylation of benzene with ethylene to ethylbenzene used in the manufacture of styrene, is one of the largest scale industrial processes. The reaction is done under the catalysis of AlCl in the presence of a proton source, ie, H2O, HCl, etc, although other catalysts have also gained significance. 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

Aromatic. Aromatic feedstreams (C-8, C-9, C-10) derived from the steam cracking of petroleum distillates are composed of styrene, iadene, vinyltoluenes (eg, meta- and i ra-methylstyrene), and their respective alkylated analogues. A typical aromatic feedstream might contain 50% reactive olefins with the remainder being alkylated benzenes and higher aromatics. 

Thermoplastic resins produced from pure monomers such as styrene, alkyl-substituted styrenes, and isobutylene are produced commercially. An advantage of these resins is the fact that they are typically lighter in color than Gardner 1 (water-white) without being hydrogenated. Among the earliest resins in this category were those made from styrene and sold as Piccolastic. Styrene and alkyl-substituted styrenes such as a-methylstyrene are very reactive toward Friedel-Crafts polymerization catalysts. 

Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). 

Styrene is manufactured from ethylbenzene. Ethylbenzene [100-41-4] is produced by alkylation of benzene with ethylene, except for a very small fraction that is recovered from mixed Cg aromatics by superfractionation. Ethylbenzene and styrene units are almost always installed together with matching capacities because nearly all of the ethylbenzene produced commercially is converted to styrene. Alkylation is exothermic and dehydrogenation is endothermic. In a typical ethylbenzene—styrene complex, energy economy is realized by advantageously integrating the energy flows of the two units. A plant intended to produce ethylbenzene exclusively or mostly for the merchant market is also not considered viable because the merchant market is small and sporadic. 

Styrene. Commercial manufacture of this commodity monomer depends on ethylbenzene, which is converted by several means to a low purity styrene, subsequendy distilled to the pure form. A small percentage of styrene is made from the oxidative process, whereby ethylbenzene is oxidized to a hydroperoxide or alcohol and then dehydrated to styrene. A popular commercial route has been the alkylation of benzene to ethylbenzene, with ethylene, after which the cmde ethylbenzene is distilled to give high purity ethylbenzene. The ethylbenzene is direcdy dehydrogenated to styrene monomer in the vapor phase with steam and appropriate catalysts. Most styrene is manufactured by variations of this process. A variety of catalyst systems are used, based on ferric oxide with other components, including potassium salts, which improve the catalytic activity (10). 

Vinyltoluene. Viayltoluene is produced by Dow Chemical Company and is used as a resia modifier ia unsaturated polyester resias. Its manufacture is similar to that of styrene toluene is alkylated with ethylene, and the resulting ethyltoluene is dehydrogenated to yield vinyltoluene. Annual production is ia the range of 18,000—23,000 t/yr requiring 20,000—25,000 t (6-7.5 x 10 gal) of toluene. 

Alkylation. Ethylbenzene [100-41 -4] the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either ia the Hquid phase ia the preseace of a Eriedel-Crafts catalyst (AlCl, BE, EeCl ) or ia the vapor phase with a suitable catalyst. The Moasanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeoHte catalyst process for Hquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process usiag zeoHte catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-5] which is obtained by dehydrogenation ia the preseace of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

Both the alkylation and dehydrogenation may be carried out using equipment designed for the production of styrene. 

Novolacs are often modified through alkylations based on reactions with monomers other than, and in addition to, aldehydes during their manufacture. Examples might be inclusion of styrene, divinyl benzene, dicyclopentadiene, drying oils, or various alcohols. Despite significant production of all of these variants, most novolac volume is produced using phenol and formaldehyde. 

The principal use of the alkylation process is the production of high octane aviation and motor gasoline blending stocks by the chemical addition of C2, C3, C4, or C5 olefins or mixtures of these olefins to an iso-paraffin, usually isobutane. Alkylation of benzene with olefins to produce styrene, cumene, and detergent alkylate are petrochemical processes. The alkylation reaction can be promoted by concentrated sulfuric acid, hydrofluoric acid, aluminum chloride, or boron fluoride at low temperatures. Thermal alkylation is possible at high temperatures and very high pressures. 

Ethylbenzene (C6H5CH2CH3) is one of the Cg aromatic constituents in reformates and pyrolysis gasolines. It can be obtained by intensive fractionation of the aromatic extract, but only a small quantity of the demanded ethylbenzene is produced by this route. Most ethylbenzene is obtained by the alkylation of benzene with ethylene. Chapter 10 discusses conditions for producing ethylbenzene with benzene chemicals. The U.S. production of ethylbenzene was approximately 12.7 billion pounds in 1997. Essentially, all of it was directed for the production of styrene. 

Absolute rate constants for addition reactions of cyanoalkyl radicals are significantly lower than for unsubstituted alkyl radicals falling in the range 103-104 M V1.341 The relative reactivity data demonstrate that they possess some electrophilic character. The more electron-rich VAc is very much less reactive than the electron-deficient AN or MA. The relative reactivity of styrene and acrylonitrile towards cyanoisopropyl radicals would seem to show a remarkable temperature dependence that must, from the data shown (Table 3.6), be attributed to a variation in the reactivity of acrylonitrile with temperature and/or other conditions. 

A5-hexenyl substituent, extensive cyclization occurs to yield the cyclopentylcarbinyl product from the yields of uncyclized and cyclized products for A5-hexenylmercury chloride, the rate constants for equation 50 have been estimated (vide supra). The SH2 reaction 49 has also been invoked to be the key step in the alkylation of -substituted styrenes by a free-radical addition-elimination sequence, namely96... 

The mechanism of anionic polymerization of styrene and its derivatives is well known and documented, and does not require reviewing. Polymerization initiated in hydrocarbon solvents by lithium alkyls yields dimeric dormant polymers, (P, Li)2, in equilibrium with the active monomeric chains, P, Li, i.e. 

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