Styrene, ? from

Dibromide formation. Dissolve 0 2 ml. of styrene in 0 5 ml. of CCI4 in a test-tube. Add slowly, drop by drop, a 10% solution of bromine in CCI4. Note the decolorisation of the bromine and absence of HBr fumes (therefore reaction by addition and not by substitution). Continue to add the bromine solution until a faint brown colour persists. Scratch the sides of the tube and cool it in ice-water. Filter off the crystals that separate and recrystallise the styrene dibromide from methanol m.p. 72 . 

One of the key benefits of anionic PS is that it contains much lower levels of residual styrene monomer than free-radical PS (167). This is because free-radical polymerization processes only operate at 60—80% styrene conversion, whereas anionic processes operate at >99% styrene conversion. Removal of unreacted styrene monomer from free-radical PS is accompHshed using continuous devolatilization at high temperature (220—260°C) and vacuum. This process leaves about 200—800 ppm of styrene monomer in the product. Taking the styrene to a lower level requires special devolatilization procedures such as steam stripping (168). 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Waters61 have measured relative rates of p-toluenesulfonyl radical addition to substituted styrenes, deducing from the value of p + = — 0.50 in the Hammett plot that the sulfonyl radical has an electrophilic character (equation 21). Further indications that sulfonyl radicals are strongly electrophilic have been obtained by Takahara and coworkers62, who measured relative reactivities for the addition reactions of benzenesulfonyl radicals to various vinyl monomers and plotted rate constants versus Hammett s Alfrey-Price s e values these relative rates are spread over a wide range, for example, acrylonitrile (0.006), methyl methacrylate (0.08), styrene (1.00) and a-methylstyrene (3.21). The relative rates for the addition reaction of p-methylstyrene to styrene towards methane- and p-substituted benzenesulfonyl radicals are almost the same in accord with their type structure discussed earlier in this chapter. 

J.N. Michaels, and C.G. Vayenas, Styrene Production from Ethylbenzene on Platinun in a zirconia Electrochemical Reactor, J. Electrochem. Soc. 131, 2544-2550 (1984). 

Styrene was successfully oxidized to the S-product both by xylene monooxygenase from P. putida mt-2 [113] and styrene monooxygenase from Pseudomonas sp.VLB120 [114] (Scheme 9.13), with the latter enzyme displaying a particularly large substrate tolerance with excellent stereoselectivity (>99% ee). In this context it is interesting to note that both xylene monooxygenase as well as chloroperoxidase are very selective for mono-epoxidation in case of presence of multiple alkene functionalities [115]. 

FIGURE 11.12 Interaction energy density versus 4-methyl styrene content. (From Raboney, M., Gamer, R.T., Elspass, C.W., and Peiffer, D.G., Phase Behavior of Brominated Poly(Isobutylene-co-4-Methylstyrene)/ General Purpose Rubber Blends. Rubber Division, Proceedings of the American Chemical Society, Nashville, TN, Sept. 29-Oct. 2, 1998, Paper No. 36.)... 

FIGURE 28.13 Dependence of conversion on reaction time of the styrene-butadiene. (From Zhang, Q. et al.. Polymer, 46, 129, 2005.)... 

Parrke, S., Held, M., Wubbolts, M.G., Witholt, B., Schmid, A. (2002) Pilot-Scale Production of (S)-Styrene Oxide from Styrene by Recombinant Escherichia coli Synthesizing Styrene Monooxygenase. Biotechnology and Bioengineering, 80, 33M1. 

Figure 44 The boron-containing styrenic monomer, 5-benzyl-2-phenyl-5-(4-vinylbenzyl)-[l,3,3]-dioxaborinane (68) used in the syntheses of a homopolymer and a copolymer with styrene. (Adapted from ref. 92.)...

Butadiene-Styrene Copolymers from Ba-Mg-Al Catalyst Systems. Figure 13 shows the relationship between copolymer composition and extent of conversion for copolymers of butadiene and styrene (25 wt.7. styrene) prepared in cyclohexane with Ba-Mg-Al and with n-BuLi alone. Copolymerization of butadiene and styrene with barium salts and Mg alkyl-Al alkyl exhibited a larger initial incorporation of styrene than the n-BuLi catalyzed copolymerization. A major portion of styrene placements in these experimental SBR s are more random however, a certain fraction of the styrene sequences are present in small block runs. 

Fig. 6 Reactivity-structure relationship for the bromination of ring-substituted styrenes (data from Ruasse et ai, 1978). Competition between bromonium and carbocation intermediates.

Fig. 7 Comparison of the X-dependence of the a-methyl effect in bromination and hydration of X-substituted styrenes (data from Ruasse et al, 1978).

Oxidation of organic compounds by dioxygen is a phenomenon of exceptional importance in nature, technology, and life. The liquid-phase oxidation of hydrocarbons forms the basis of several efficient technological synthetic processes such as the production of phenol via cumene oxidation, cyclohexanone from cyclohexane, styrene oxide from ethylbenzene, etc. The intensive development of oxidative petrochemical processes was observed in 1950-1970. Free radicals participate in the oxidation of organic compounds. Oxidation occurs very often as a chain reaction. Hydroperoxides are formed as intermediates and accelerate oxidation. The chemistry of the liquid-phase oxidation of organic compounds is closely interwoven with free radical chemistry, chemistry of peroxides, kinetics of chain reactions, and polymer chemistry. 

The effects of amendments to the Environmental Protection Act (1990), which relate to pollution control and styrene emissions from installations, on UK fibre reinforced plastics processors are examined. Possible cost-effective abatement solutions are briefly considered. 

Table XIV. Variation in Styrene Absorption from Methanol Solution by Polyethylene with Time3...

As polymerization proceeds, the total volume of polystyrene polymer particles increases rapidly at the expense of the styrene monomer from the solution. What happens next depends on several factors, mainly composition and stirring. It was found that for SIN formulations having an elastomer content greater than about 15%, no further changes occur and elastomer material will remain the continuous phase, regardless of the extent of agitation. 

EH and GTr activities were assayed after the method of James et al. (33), which in the former case was a modification of Oesch et al. (34) method. Incubation mixtures contained lpmole styrene- C-oxide (specific activity 47.7pCi/mmole) in 2pl tetrahydrofuran. Styrene-1 C-oxide was prepared from 14c-styrene (purchased from California Bionuclear Corp.) after the method of Oesch et al. (34). Incubations were carried out at 25°C for 15 minutes. 

Varner, S.L., Breder, C.V. and Fazio, T. (1983). Determination of styrene migration from food-contact polymers into margarine, using azeotropic distillation and headspace gas chromatography, J. Assoc. Ojf. Anal. Chem., 66, 5, 1067-1073. 

Moore, E.R., Styrene Polymers from Encyclopedia of Polymer Science and Engineering, 16, 2 ed., John Wiley Sons (1989)... 

The concentration of the surfactant in the monomer phase was found to be critical to the formation of a stable polymer foam [129,130]. At least 4% surfactant, relative to the total oil phase, was required for PolyHIPE formation, whereas formulations containing above 80% resulted in the formation of an unconnected or closed-cell material. Surfactant levels between 20 and 50% were deemed to be optimum at all internal phase volumes. Additionally, Litt et aL [131] demonstrated that block copolymer surfactants can be used to prepare water-in-styrene HIPEs. From these, highly porous uncrosslinked polystyrene PolyHIPE materials were synthesised. 

Figure 11. Styrene incorporation from butadiene-styrene (75/25) in cyclohexane solutions at 30-121°C (59).

One method is to measure chain-transfer coefficients with low-MW analogues of the polymer. Thus Gilchrist (140) measured the rate at which 14C labelled decane was incorporated into polyethylene in the free-radical polymerization, and hence obtained an estimate of the transfer coefficient with methylene groups this was in fair agreement with another estimate obtained from the effect of the addition of fractions of linear polyethylene on the Mn of the branched polyethylene, which could be separated from linear polymer plus grafted branched polymer by column extraction. Low MW polymer may be used as a transfer agent Schulz and co-workers (189) obtained chain-transfer coefficients in styrene polymerization from the effect of added low MW polymer on Mn. 

R. Balart, L. Sanchez, J. L6pez, and A. Jimenez, Kinetic analysis of thermal degradation of recycled polycarbonate/acrylonitrile-butadi-ene-styrene mixtures from waste electric and electronic equipment,... 

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