Styrene p-methoxystyrene

Arya et al. used solid phase synthesis to prepare immobilised dendritic catalysts with the rhodium centre in a shielded environment to mimic nature s approach of protecting active sites in a macromolecular environment (e.g. catalytic sites inside enzymes) [51], Two generations PS immobilised rhodium-complexed dendrimers, 6 and the more shielded 7, were synthesised.The PS resin immobilised rhodium-complexed dendrimers were used in the hydroformylation of styrene, p-methoxystyrene, vinyl acetate and vinyl benzoate using a total pressure of 70 bar 1 1 CO/H2 at 45 °C in CH2C12. 

Results of Dulog, Kern et ah, and a few others (27, 31) are summarized in Table I. From the ra values, toward the unsubstituted styrene-peroxy radical, the most reactive styrene—p-methoxystyrene—is three times as reactive as the least reactive, m-nitrostyrene. Thus, the best electron donor shows the highest reactivity (lowest enthalpy of activation) toward the electron-accepting styrene-peroxy radical. The deviations from unity of the rarb products measure the effects of substitution on the selectivity of the peroxy radicals. These products depart more from unity with increasing differences in the electron-donating and accepting properties of the nuclear substituents. The same trends appear within the other styrene combinations. 

It is interesting to note that this relation was verified for polymerizations of styrene, p-methoxystyrene, and isobutylvinylether with iodine by Kanoh and Higashimura (19). They have demonstrated that the apparent rate constants of termination, propagation, and monomer transfer increased with increasing dielectric constant of solvent, and the rates of the increase for these three rate constants were of the order of Eq. (21). 

Predict the order of reactivity (and justify your prediction) of the given monomers, (a) Styrene, 2-vinylpyridine, 3-vinylpyridine, and 4-vinyl pyridine in anionic polymerization, (b) Styrene, p-methoxystyrene, p-chlorostyrene, and p-methylstyrene in cationic polymerization. 

Similar results were reported in polymerizations of styrene with CH3COCIO4, CF3SO3H, CF3COOH, CISO3H, and FS03H. Pseudocationic mechanism also takes place in polymerizations of some styrene derivatives, like p-methyl styrene, p-methoxystyrene, and p-chlorostyrene with these protonic acids. ... 

Living cationic polymerizations have been carried out with a number of monomers, such as isobutylene, styrene, p-methyl styrene, p-methoxystyrene, A -vinylcarbazole, and others [137, 138]. To achieve living conditions, it is necessary to match the propagating carbon cation with the counterion, the solvent polarity, and the reaction temperature. Some examples are offered in Table 4.2. 

PIZ Pizzoli, M. and Ceccorulli, G., Solution properties of styrene-p-methoxystyrene random... 

In a related photoreaction, hexafluorobutadiene forms the [2+4] adduct with p (Al.lV-dimethylamino)styrene in 11% yield, whereas no such adduct could be detected for the same reaction with p-methoxystyrene [124] (equation 104) The analogous thermal reaction at 120 °C leads only to [2+2] adducts... 

Similarly, hydroboration of p-methoxystyrene with HBcat using zwitterionic [(P-P)Rh(//6-catBcat)] ((4), P-P = dppe, dippe) or [(dippe)Rh(r/3-2-IVIc-a 11 y 1)] (dippe= l,2-bis(diisopropylphosphine)ethane) gave 99% of the internal hydroboration product. Complications arose in studying reactions of hindered styrenes due to the appearance of not only the hydroboration products (A and B), but also the dehydrogenative borylation products C and D (Scheme 5).32 The ratio of products was found to be highly catalyst dependent (Table 2).33... 

Using styrene as substrate both 6 and 7 could be recycled four times, apparently without loss in activity or selectivity (>99% conversion after 20 hours b l ratio i 18 1). When p-methoxystyrene was used as a substrate the first three cycles did not suffer... 

For the polymerisation of styrene (SnC -F O-PhNC -CC at 0°) kjkv for anisole was found [85] to be 1.62. It is highly probable that the big difference between this and the value for isobutene reflects mainly the difference between the ps for the two monomers. The very low value of kjkv in the polymerisation of isobutene - or the very large kv of isobutene - accounts for the observation [86] that, whereas styrene polymerising cationically in the presence of preformed poly-p-methoxystyrene will form grafts by reacting with pendent rings, isobutene will not do so. 

Graft copolymers of nylon, protein, cellulose, starch, copolymers, or vinyl alcohol have been prepared by the reaction of ethylene oxide with these polymers. Graft copolymers are also produced when styrene is polymerized by Lewis acids in the presence of poly-p-methoxystyrene. The Merrifield synthesis of polypeptides is also based on graft copolymers formed from chloromethaylated PS. Thus, the variety of graft copolymers is great. 

Some branching has been detected in the polymerizations of styrene and anethole (P-methyl-p-methoxystyrene), indicating intermolecular aromatic substitution by a propagating carbocation on the aromatic ring of another polymer chain [Hatada et al., 1980 Kennedy and Marechal, 1982]. 

When DISN reacts with electron-rich styrenes such as p-methoxystyrene, good yields of reduced pyrazines 117, often accompanied by their oxidized forms, are obtained. However, reaction with electron-deficient styrenes like p-fluorostyrene give the 2-amino-3-(2-arylaziridin-l-yl)maleonitriles (118) (72JA3242 84JOC813). 

Those olefins having double bonds sufficiently electron rich to react significantly with these salts include the common monomers, alkyl vinyl ethers (28,79-81), N-vinylcarbazole (82-84) p-methoxystyrene (21,67), indene (34,74,85), cyclopen tadiene (85,86), and vinylnaphthalenes (87). Styrene itself (60,76,77,88-91), cr-divinylbenzene (92), a-methylstyrene (88), linear conjugated dienes (93) and a-olefins are much less reactive (i.e. formation of their corresponding carbocations is energetically unfavourable), and undo- normal conditions give at best slow reactions and low yields of polymer. 

The change in surface acidity with water content was also demonstrated by the ability of kaolinite to promote acid-catalyzed polymerization (236). Styrene, p-methylstyrene, and p-methoxymethylstyrene polymerized vigorously on kaolinite that was dried at 110°C. At 0.2% wt water content, p-methylstyrene and p-methoxystyrene polymerized and at 0.6% wt water content, only p-methoxystyrene polymerized. The polymerization results are consistent with lower acidity at higher water contents since the susceptibility of these monomers to acid-catalyzed polymerization is in the order p-methoxystyrene > p-methylstyrene > styrene. 

PMMA poly(methyl methacrylate) p-MOS p-methoxystyrene PS poly(styrene)... 

Preparation of star polymers of p-methoxystyrene (p-MOS) and p-tert-butoxy-styrene (fBOS) using two different bifunctional vinyl compounds 1 and 5 was reported by Deng et al. [5]. 

The rate constants of initiation of styrene by triflic acid are estimated to be roughly k,- 10 M sec-1 at 0° C in CH2CI2 this is 10,000 times smaller than the corresponding propagation rate constant under similar conditions [17]. However, it does not take into account the higher order kinetics in acid [134]. Initiation of more nucleophilic monomers is faster, with ki = 103 M l-sec-1 for a-methylstyrene [21] and kj = 5104 M -sec l for p-methoxystyrene [23], as determined by stopped-flow methods at ambient temperature in CH2CI2 and C2H4CI2. 

VE vinyl ethers pMS p-methylstyrene St styrene aMS a-methylstyrene pMOS p-methoxystyrene pBOS p-r-butoxystyrene IB isobutene. 

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