Reactions of polystyrene

D. Acylation Reaction of Polystyrene with Maleic Anhydride and Acetic Anhydride... 

Bis(2,2 -bipyridyl)ruthenium(II) was anchored onto poly(4-vinyIpyridine) (PVP) (6) 28>29), but the polymer complex is not suitable as photocatalyst, because it is susceptible to photoaquation. A polymer complex containing Ru bpy) + pendant groups was first prepared by reaction of polystyrene (PSt) as shown in Eq. (15)30). 

Non-aromatic organolithium compounds can be prepared by transmetallation of resin-bound stannanes [25] or by deprotonation of alkynes [26], triphenylmethane [27], or other resin-bound C II acidic compounds with lithium amides or similar bases (Figure 4.3). The reaction of polystyrene-bound trialkylboranes with diethylzinc yields resin-bound alkylzinc derivatives [28]. 

In addition to the alkylations discussed above, some special reactions have been reported that enable the solid-phase synthesis of cycloalkanes. These include the intramolecular ene reaction and the cyclopropanation of alkenes (Figure 5.5 see also [44]). Cyclobutanes have been prepared by the reaction of polystyrene-bound carbanions with epichlorohydrin, and by [2 + 2] cycloadditions of ketenes to resin-bound alkenes. 

Imidazoles have been alkylated and arylated on cross-linked polystyrene at nitrogen and at C-2. Illustrative examples of these transformations are listed in Table 15.12. The reaction of polystyrene-bound 4-iodobenzoate with /V-methylimidazole in the presence of Pd(0) (DMF, 120 °C, 16 h) leads to 4-arylimidazoles [141]. If Cul is... 

The synthetic strategies used for the preparation of pyrans on insoluble supports have mainly been hetero-Diels-Alder reactions of enones with enol ethers and ringclosing olefin metathesis (Table 15.33). Benzopyrans have been prepared by hetero-Diels-Alder reactions of polystyrene-bound o-quinodimethanes with aldehydes. The required quinodimethanes were generated by thermolysis of benzocyclobutanes, which were prepared in solution [308]. Other solid-phase procedures for the preparation of benzopyrans are the palladium-mediated reaction of support-bound 2-iodo-phenols with 1,4-dienes (Entry 5, Table 15.33) and the intramolecular Knoevenagel... 

An equimolecular amount of tertbutyl oxide and tert-butyl peroxide radicals are formed, which can initiate the polymerization of styrene consequently, considering that the chain termination reaction of polystyrene proceeds by coupling, it results that most of the polystyrene molecules will contain one or two terminal peroxide groups. These have been used for a second step polymerization, e.g. of methyl methacrylate. In this case also, it seems that the macro end radical should be much more efficient for initiating polymerization than the small tert-butyl oxide radical (47). The styrene content of the block copolymer was about 35%. 

Show the steps in the mechanism for the formation of chloromethylated polystyrene by the reaction of polystyrene with formaldehyde and HC1. 

Supported oxo-rhenium catalysts in heterogeneous systems have also been reported, for example, the polystyrene-supported (catecholato)oxo-rhenium(VII) complexes (38), obtained from the reaction of polystyrene-supported catechol with [ReOCl3(PPh3)2], which catalyze alcohol oxidation to ketones or aldehydes with dimethylsulfoxide and epoxide... 

While linear polymers are synthesized from monomeric units with functionality 2, polymerization reaction of a mixture of monomers with functionality 2 and higher than 2 gives rise to cross-linked polymers. For example, let us consider the case of a polymerization reaction of polystyrene... 

Block copolymers with hydroxyl segments were prepared by various ways An example utilizes the copper-catalyzed sequential copolymerizations of nBA and 2-[(trimethylsilyl)oxy]ethyl acrylate by the macroinitiator method into B-31 to B-33. The copolymers were then hydrolyzed into amphiphilic forms by deprotection of the silyl groups.313 A direct chain-extension reaction of polystyrene and PMMA with HEMA also afforded similar block copolymers with hydroxyl segments (B-34 and B-35).241-243 In block polymer B-36, a hydroxy-functionalized acrylamide provides a hydrophilic segment.117 Block copolymers of styrene and p-acetoxystyrene (B-37 to B-39), prepared by iron... 

N-oxide salts (HBTU and TBTU, respectively) [39], or from l-hydroxy-7-azabenzotriazole (HOAt) such as N-[(dimethylamino)-lH-l,2,3-triazolo[4,5-fe] pyridino-l-y]methylene]-N-methy]methanaminium tetrafluoroborate N-oxide (HATU) [40], are well established reagents. They are especially devoted to peptide coupling reactions due to their efficiency and the low degree of undesirable race-mization produced in the final peptide compared to the use of classical carbodi-imide-coupling methods. Therefore, as the polystyrene-supported HOBt is an often used polymeric reagent (Section 7.6.3) [41], its transformation in a supported HOBt and tetramethylurea-derived aminium salt analog to HBTU and TBTU resulted directly. Thus, the reaction of polystyrene-2% divinylbenzene copolymer resin P-HOBt (20) with tetramethylchloroformamidinium tetrafluoroborate (21) (4 equivalents) in the presence of triethylamine gave polymeric N-[(lH-benzotriazol-l-yl)(dimethylamino)methylene]-N-methylmethanaminium tetrafluoroborate N-oxide (P-TBTU, 22) (Scheme 7.6) [42],... 

H.J. Rader, J. Spickermann and K. Mullen, MSLDI-TOF Mass spectrometry in polymer analytics, I. Monitoring the polymer-analogous sulfonation reaction of polystyrene, Macromol. Chem., Phys., 1995, 196, 3967-3978. 

Scheme 6.20 Acid-catalyzed condensation cross-linking reaction of polystyrene by an added cross-linker.

Polystyrene - The acid-catalysed reaction of polystyrene over zeolites has also been examined over a range of materials.In general, the same shifts in the product distribution as compared to thermal degradation that were observed when silica-alumina catalysts were used were seen when zeolites were employed. The yield of styrene monomer decreased, and the amounts of benzene and indan derivatives increased. The extent to which the catalyst affected the degradation was dependent on the catalyst-polymer contacting pattern. The product distributions observed over particular zeolites are summarized as examples below. 

The preparation of the starting material, poly(vinylacetophenone), may be carried out by a Friedel-Krafts reaction of polystyrene in carbon disulfide with acetyl chloride and aluminum chloride by the method of Kenyon and Waugh [95a]. 

The reaction of polystyrene with MCDE or methylal in EDC dispersed in excess of the above catalytic mixture at 80°C yields beaded... 

A similar situation is observed for the reaction of polystyrene with MCDE in cyclohexane (Table 7.5) [155]. We can see again that the lower is the catalyst concentration in the reaction medium, the lower is the abihty of the resulting networks to absorb both good and poor solvents, in spite of the fact that the conversion of the initially introduced chloromethyl groups is also lower. The paradox here consists in that smaller swehing corresponds to smaher crosshnking density, rather than vice versa. 

As already mentioned in Chapter 6, Section 4, appropriate solvents for conducting Friedel—Crafts crosslinking reaction of polystyrene are EDC, tetrachloroethane, nitrobenzene, and cyclohexane (at an elevated temperature). While the products prepared in the first two solvents are identical in aU their swelling behavior, the character of swelling of materials obtained in nitrobenzene is different. 

Kirschning and coworkers have also reported the preparation of reagent systems generated in situ from (diazidoiodo)benzene and tetraalkylammonium halides [51], Particularly useful is a sfable polymer-bound bis(azido)iodate (30), which can be readily prepared by the reaction of polystyrene-supported iodide 28 with (diazidoiodo)benzene generated in situ from (diacetoxyiodo)benzene and azidotrimethylsilane (Scheme 5.17) [51]. 

There are some interesting reports in the literature on reactions carried out on the backbones of polystyrenes. There are also many reports in the literature on aromatic substitution reactions of polystyrene. Only a few, however, are in industrial practice. 

Sulfonation reactions of polystyrene and its copolymers with divinyl benzene are carried out commercially to prepare ion exchange resins. Partial sulfonations of polystyrenes are achieved in the presence of ethers. When more than 50% of the aromatic rings are sulfonated, the polymers become water soluble. At lesser amounts of sulfonation (25-50%), the polymers are solvent soluble. ... 

Discuss chloromethylation reactions of polystyrene and its copolymers, showing all chemical reactions. 

Show examples of the Friedel-Craft reactions of polystyrene and chloromethylated polystyrene. 

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