Styrene, Table

The rate constants for reaction of XA with cyclohexane (Table 5) and styrene (Table 6) indicate that it is less reactive than DMFL, for example. 

Rhodium complexes (lmol%) prepared in situ from [Rh(GOD)2]BF4 and the respective ligands 80-83 were employed in the enantioselective hydroboration-oxidation of styrene (Table 7).114-117... 

As with monomer reactivities it is seen that the order of radical reactivities is essentially the same irrespective of the monomer used as reference. The order of substituents in enhancing radical reactivity is the opposite of their order in enhancing monomer reactivity. A substituent that increases monomer reactivity does so because it stabilizes and decreases the reactivity of the corresponding radical. A consideration of Table 6-4 shows that the effect of a substituent on radical reactivity is considerably larger than its effect on monomer reactivity. Thus vinyl acetate radical is about 100-1000 times more reactive than styrene radical toward a given monomer, while styrene monomer is only 50-100 times more reactive than vinyl acetate monomer toward a given radical. A comparison of the self-propagation rate constants (kv) for vinyl acetate and styrene shows that these two effects very nearly compensate each other. The kp for vinyl acetate is only 16 times that of styrene (Table 3-11). 

For co-oxidation of nuclear-substituted styrenes, Table I shows a consistently decreasing rarh product as the polarity difference increases in pairs of substituted styrenes, the minimum value being about 0.4. This effect cannot be steric and must be polar. The polar effects could be caused by transmission of substituent effects through the O—O link, to some tendency of different styrenes to associate in solution—i.e., actual... 

Engineering Thermoplastics Polyolefins and Styrenics Table 2.3 Materials with High Glass Transition Temperatures (26)... 

Cu complexes with bis-oxazoline ligands 6 that were first reported by Masamune and co-workers [39] have incited considerable interest because of the exceptional enantiocontrol that can be achieved with their use as catalysts for cyclopropanation reactions. Concurrent investigations by Evans [40], who added 7 Masamune, who provided 8 and 9 [41] and Pfaltz [42], who investigated a similar series, established that the C2-symmetric bis-oxazoline ligands are suitable alternatives to semicorrin ligands for Cu in creating a highly enantioselective environment for intermolecular cyclopropanation. For the first time, diazoacetates with ester substituents as small as ethyl could be used to achieve enantioselectivity >90% ee in reactions with styrene (Table 5.4). 

The only substrate which has been hydroformylated using chiral cobalt catalysts with an optical yield comparable to those obtained with other metals is styrene (Table 1) in fact, in this case, optical yields up to 15% were obtained working in the presence of ethyl orthoformate15) to avoid racemization of 2-phenylpropanal. The changes in the prevailing absolute configuration of the synthesized aldehyde observed both in the styrene and 2-phenyl-1-propene hydroformylation upon... 

A rather large number of asymmetric ligands have been tested in the hydroformylation of styrene (Table 3), optical yields between 20 and 30% being easily obtained. 

The overall reactivities of these radicals in their ummolecular 5-hexenyl cyclization processes reflects those same factors which affect the reactivity of partially-fluorinated radicals in their bimolecular addition reactions with alkenes, such as styrene. Table 17 indicates this clearly, and it also reflects the general leveling effect which would be expected for the more facile unimolecular cyclization processes which have log A s about 1-2 units larger than those for the bimolecular additions. 

However, the (M)-phenyl methyl sulfoxide has the opposite configuration to (Mi-styrene oxide (Fig. 8, inset) (49). A possible structural difference between styrene and thioanisole is the fact that the ethylene group in styrene is in the plane of the phenyl ring while the S-methyl group in thioanisole is perpendicular to the phenyl group. If the Mb mutants discriminate this steric difference, one could expect (S)-sulfoxide formation if cyclic sulfides are employed as substrates, since the cyclic sulfides should have planar structures (Fig. 8c) similar to styrene. Table III lists representative results of cyclic and acyclic sulfide... 

During our further studies of ketone catalysts, ketone 16 was found to be highly enantioselective for a number of acyclic and cyclic d.s-olefins (Table 10.6).73-74 It is important to note that the epoxidation is stereospecific with no isomerization observed in the epoxidation of acyclic systems. Ketone 16 also provides encouragingly high ee s for certain terminal olefins, particularly styrenes.74-75 In general, ketones 1 and 16 have complementary substrate scopes. In our subsequent study of the conformational and electronic effects of ketone catalysts on epoxidation, ketone 17, a carbocyclic analog of 16, was found to be highly enantioselective for various styrenes (Table 10.7).76... 

The capabilities of 5-8 for enantioselective cyclopropanation were determined (34) from reactions at room temperature of d- and/or /-menthyl diazoacetate (MDA) with styrene (Table 1), which allows direct comparison with results from both the Aratani (A-Cu) and Pfaltz (P-Cu) catalysts (19, 24). Cyclopropane product yields ranged from 50 to 75%, which were comparable to those obtained with chiral copper catalysts, but enantiomeric excesses were considerably less than those reported from use of either P-Cu or A-Cu. Furthermore, these reactions were subject to exceptional double diastereoselectivity not previously seen to the same degree with the chiral copper catalysts. Although chiral oxazolidinone ligands proved to be promising, the data in Table 1 suggested that steric interactions alone would not sufficiently enhance enantioselectivities to advance RI12L4 as an alternative to A-Cu or P-Cu. 

The nitrido complexes 16-21, as shown in Section 6.3, which bear various substituents on the para (R1) and/or ortho (R2) positions of a benzene ring of complex 15 were employed in the asymmetric aziridination of styrene (Table 6.2). The reaction of styrene with complex 16 or 17 gave lower product yields and enantioselectivities compared to the reaction with the complex 15. Complex 18 decreased the yield of the aziridination, but the enantioselectivity was not affected however, when complex 19 was employed, the yield and the selectivity were low. In the case of 20, the enantioselectivity was moderate but the yield was very low complex 21, which bears Jacobsen s ligand, showed a similar result with complex 20. Thus far, complex 15 is the best nitrogen source for the asymmetric aziridination of styrene. 

Mouron et al. [105] and Wang et al. [106] have used dodecyl mercaptan (DDM) as the costabilizer in styrene and MMA miniemulsion polymerizations, respectively. Some of the results are shown in Table 8 and Table 9. For styrene (Table 8), the macroemulsion is compared with miniemulsions containing varying levels of DDM (costabilizer). In this case, the macroemulsion has a broader particle size distribution than all but one of the miniemulsions. For MMA (Table 9), miniemulsions and the equivalent macroemulsions have been compared at varying initiator concentrations. In this case, the macroemulsions... 

Number of particles. Emulsion polymerization of 1,4-DVB yields significantly more and smaller polymer particles than that of styrene (table I). 

To understand the difference of stability of the miniemulsions prepared by the two methods we have studied the miniemulsions by freeze fracture and electron microscopy (9) euid measured the size of the particles. For all the systems studied, the dimensions of the particles are smaller for the miniemulsions prepared by the second method for instance in the case of styrene (Table IV) the dieuneter 0 of the particles is 310 nm against 840 nm. Such a difference in the particle size explains the difference of stability of the miniemulsions prepared by the two methods. 

Acrolein-containing latex particles were used for immobilization of proteins. The latex particles were prepared by emulsifier-free polymerization of acrolein and styrene (Table I). Fluorescent latex particles were prepared by mixing fluorescent dyes such as Hostalux KCB (Hoechst) or coumarin-6 into styrene before the emulsion polymerization (Table I). To increase the immunological sensitivity of the protein-conjugated latex particles, a hexyl group was introduced between the latex particle and the protein (Protein-spacer-latex). Proteins such as human serum albumin (HSA), anti-human serum albumin (anti-HSA-IgG), and a fragmented antibody (anti-HSA-... 

The results from the aromatic disulfides on both styrene (Table II) and MM A (Table 12), on which Japanese teams performed a lot of investigations, are move interesting. 

In the examples described above, the transition is shown from ideal (n = /2) to nonideal (n > /2) behavior. There are, however, systems for which ideal emulsion polymerization practically cannot be achieved. It is nevertheless possible to describe the kinetics of such systems quantitatively. Recently, Gerrens has obtained values of the propagation and termination rate constants at diflFerent temperatures for vinyltoluene and vinylxylene (28). The termination rate of polymer radicals of these monomers is so low that even at small rates of initiation in small particles, n is larger than /2. From measurements of the reaction rate before and after injection of additional initiator in the polymerizing system it was possible to calculate n both at the original and at the boosted initiation rate with the aid of Equation 5. Consistent results were obtained when the additional amount of initiator was varied. From these rate data, the termination rate constant was found to be 10 and 17 liters mole- sec. at 45° C. for vinyltoluene and vinylxylene, respectively. These values are to be compared with 10 for styrene (Table IV). 

For the dimerization of 4,4 -dimethoxystilbene, it has been possible to demonstrate spectroelectrochemically [115] and at the rotating ring-disk electrode [116] that the product is formed mainly by radical dimerization of the intermediate radical cations [path B, Eq. (13)]. Fast derivative CV, however, supports for the same olefin a complex ECE pathway [path A, Eq. (13) [117]. Depending on the oxidation potential and the kind of the nucleophiles (acetate, water, or methanol), a tetrahydronaphthalene derivative (Table 6, number 3) [118], a monomer diacetate [118], a tetrahydrofuran [115], or a dimer dimethoxy compound is found. When methanol is replaced by aqueous dichloromethane or by aqueous acetonitrile emulsions as solvent, styrene (Table 6, number 4) [119a] and a-methylstyrene [119b] yield 2,5-diphenyltetrahydrofurans. In some cases cyclization occurs by electrophilic aromatic substitution (analogous to Table 6, number 3). 

The copolymerization of styrene and acrylonitrile in the presence of AlEt under UV irradiation yields equimolar, alternating copolymers when the initial comonomer charge is equimolar or contains excess acrylonitrile and products with compositions intermediate between that of the equimolar copolymer and that of the radical copolymer when the initial charge is rich in styrene (Table III) (lO). The intermediate compositions may represent mixtures of equimolar and radical copolymers, block copolymers generated as shown in Eq. (6)-(l0) or random copolymers resulting from copolymerization of complexes and monomers. 

Model II. Some monomers have high monomer-water mutual solubilities compared to styrene (Table I) (5). For the swelling of these systems, neglect of the effect of water dissolved in swollen particles as well as in the monomer phase could lead to significant errors. Therefore, free energy terms describing the water-monomer and water-polymer interactions should be included in the equilibrium equations to cover a wide range of monomers. 

The photochemical extrusion of nitrogen from silyl-substituted diazoacetates (hv > 300 nm) in the presence of various alkenes leads mainly to the formation of cyclopropanes (Table 4). Reactions of trimethylsilyl- and triisopropylsilyldiazoacetates with monosubstituted alkenes such as hex-1-ene or styrene (Table 4, entries 1-3) show interesting results. The formation of the thermodynamically less favored Z-isomer increases with growing steric demand of the silyl substituent. The cyclopropanation of ( )- and (Z)-but-2-ene (Table 4, entries 5 and 6) reveals that the addition reaction does not proceed completely stereospecifically. Small amounts of the wrong diastereomer can be detected, which is believed to arise from the triplet spin state of the carbene. Insertion into allylic C-H bonds occurs in the case of di- or trisubstituted alkenes (Table 4, entries 4-7). 

The rate constants for reaction of XA with cyclohexane (Table 5) and styrene (Table 6) indicate that it is less reactive than DMFL, for example. This observation is easily understood by consideration o Fig. 4. T e owest unoccupied orbital of XA (centre. Fig. 4B) has a ig er energy t an t e... 

In the end of 1960s, Nikolaev et al.29 and Ito et al.30 independently demonstrated an appreciable effect of the reaction medium on the reactivity ratios in the copolymerization of methyl methacrylate and styrene (Table 19). Ito et al. found that the relative reactivity of methyl methacrylate toward the polystyryl radical is correlated with the transition energies ET for the longest wavelength absorption band for pyridinum TV-phenolbetaine in solvents. They suggested that the polarized structure of methyl methacrylate monomer becomes important in the transition state. Bonta et al.32 also demonstrated that there is an appreciable solvent effect on the reactivity ratio in the styrene-methyl methacrylate copolymerization in non-... 

In a similar way, a-halogen oligomers of acrylates [ 162], previously synthesized by ATRP, were used in ATRC however, the yield of the radical coupling was lower than that of styrene (Table 14). A similar result was observed for... 

Reaction temperature. The most active catalyst 3W was used for these investigations. This Pd/C catalyst was tested at different reaction temperatures in the coupling of p-bromoacetophenone (Table 3, entries 1-4) and bromobenzene with styrene (Table 3, entries 5-7.) The catalytic runs were performed using only 0.1 mol% palladium (instead of 1.0 mol% relative to the bromoarene as in the catalytic experiments described before Table 1 and 2.)... 

The solvent also affects palladium leaching. For more precise determination, conditions favoring palladium leaching (T = 80 °C, as mentioned above) were applied in the coupling of p-bromoacetophenone and styrene (Table 4, entries 1-... 

In attempts to copolymerize various diallyl esters with styrene it was found that the reactivity was quite low. Further, the rate and degree of copolymerization was roughly inversely related to the concentration of diallyl ester. With increasing styrene levels, the tendency toward cyclopolymerization decreased [47]. In effect, the diallyl esters act as chain-transfer agents for the polymerization of styrene. Table V gives the chain-transfer constants and the reactivity ratios for the copolymerization with styrene. 

In view of the speed with which the weak V-H bonds in (P-P)(CO)4VH transfer H to styrene (Table 1.3 above), we have tried these hydrides with the cyclization substrates 1 and 8. StoichiometricaUy they give similar results, but more quickly, even at lower temperatures [13]. For example, treatment of 1 with dppe(CO)4VH... 

Because of the above heat transfer problems, bulk polymerization of vir l monomers is restricted to those with relatively low reactivities and enthalpies of polymerization. This is exemplified by the homogeneous bulk polymerization of methyl methacrylate and styrene (Table 10.1). Some polyurethanes and polyesters are examples of step-reaction polymers that can be produced by homogeneous bulk polymerizations. The products of these reactions might be a solid, as in the case with acryhc polymers a melt, as produced by some continuous polymerization of styrene or a solution of polymer in monomer, as with certain aUcyd-type polyesters. 

The unzipping or zip length S gives the number of monomer molecules eliminated per kinetic chain. Low values of S mean that little monomer is eliminated, but not necessarily that there is little degradation [compare, for example, the zip length of poly(styrene) (Table 23-4) with that of the products formed during degradation (Table 23-3)]. 

Using this novel copolymerization technique, a range of narrow polydispersity poly(4-hydroxystyrene-co-styrene) have been synthesized (PD = 1.1 to 1.3), with a wide variety compositions, ranging from 90 10 to 55 45 (4-hydroxystyrene styrene). Table 1. 

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