Phosphonium ion polymers

Add excess ethylene oxide to preformed phosphonium ion polymer in benzene. 

Analysis of Phosphonium Ion Polymers. The equivalent weight of a reagent must be known for synthetic use. That is not necessarily easy with polymer-bound reagents. Polymer-bound phosphonium ions, however, can be analyzed well. The halide counterions at the phosphonium sites can be determined titrimetrically after they have been displaced from a small sample of the reagent by another anion such as nitrate (13). The solvent swollen reagent can be analyzed qualitatively by C-13 and P-31 NMR, and P-31 NMR can even be used quantitatively (although with less accuracy than the titrimetric analysis for halide) by peak area comparison with an internal standard (391. Elemental analyses for phosphorus and halide should be used periodically to confirm the results of analyses performed in the chemist s own laboratory. 

Phase transfer catalyzed reactions in which ylides are formed from allylic and ben-zylic phosphonium ions on cross-linked polystyrenes in heterogeneous mixtures, such as aqueous NaOH and dichloromethane or solid potassium carbonate and THF, are particularly easy to perform. Ketones fail to react under phase transfer catalysis conditions. A phase transfer catalyst is not needed with soluble phosphonium ion polymers. The cations of the successful catalysts, cetyltrimethylammonium bromide and tetra-n-butylammonium iodide, are excluded from the cross-linked phosphonium ion polymers by electrostatic repulsion. Their catalytic action must involve transfer of hydroxide ion to the polymer surface rather than transport of the anionic base into the polymer. Dicyclohexyl-18-crown-6 ether was used as the catalyst for ylide formation with solid potassium carbonate in refluxing THF. Potassium carbonate is insoluble in THF. Earlier work on other solid-solid-liquid phase transfer catalyzed reactions indicated that a trace of water in the THF is necessary (40). so the active base for ylide formation is likely hydrated, even though no water is included deliberately in the reaction mixture. 

Benzyl phosphonium ions, polymer-bound, alkenes prepared, l65t Benzyne... 

Overall, there is no large difference in activity between lipophilic phosphonium and ammonium ions, although the phosphonium ions appear to be more active in locations close to the polymer backbone. 

When the reactions of alkyl bromides (n-Q-Cg) with phenoxide were carried out in the presence of cosolvent catalyst 51 (n = 1 or 2,17 % RS) under triphase conditions without stirring, rates increased with decreased chain length of the alkyl halide 82). The substrate selectivity between 1-bromobutane and 1-bromooctane approached 60-fold. Lesser selectivity was observed for polymer-supported HMPA analogue 44 (5-fold), whereas the selectivity was only 1,4-fold for polymer-supported phosphonium ion catalyst 1. This large substrate selectivity was suggested to arise from differences in the effective concentration of the substrates at the active sites. In practice, absorption data showed that polymer-supported polyethylene glycol) 51 and HMPA analogues 44 absorbed 1-bromobutane in preference to 1-bromooctane (6-7 % excess), while polymer-supported phosphonium ion catalyst 1 absorbed both bromides to nearly the same extent. 

Polymer-supported multi-site phase-transfer catalysis seems to require the use of less material in order to provide activity comparable to others253 (Table 27). Quaternary phosphonium ions on polystyrene latices, the particles of which are two orders of magnitude smaller than usual, were shown to be capable of higher activity coagulation of the catalysts under reaction conditions was minimized by specific treatment904. The spacers may also contain ether linkages. 

UV spectroscopy shows that quaternary phosphonium ions are present but, of course, does not prove that they are joined to polymer chains. The authors fractionated their polymers with a THF/water solvent-non solvent combination. They had found that the model compound described above could be quantitatively separated from phosphorus free poly(methylenemalonie ester). After fractionation the phosphorus content fell, but when the molecular weight was determined by vapour pressure osmometry, it was found that there was approximately one phosphonium group per chain. The absorption coefficient of the model compound was used to calculate the phosphorus content of the product. 

A problem in interpreting the effect of different counterions on the mechanical properties of ionic polymers is the difficulty in evaluating how cation-anion interactions are changing from counterion to counterion. For example, metal counterions differ in ionicity as well as in size and valence, and they can have a partially covalent character. In contrast, quaternary phosphonium ions have a number of desirable characteristics that make them particularly attractive as model systems for the study of counterion effects. They have an essentially full positive charge on the heteroatom so partially covalent interactions, fractional charge transfer between the counterion and anion, and hydrogen bonding do not come into play. Furthermore, with quaternary ions there is no possibility of the tautomerism that can occur with nonquatemary ammonium or phosphonium counterions. 

Tomoi, M., and W. T. For Mechanisms of Polymer-Supported Catalysis 1. Reaction of 1-Bromooctane with Aqueous Sodium Cyanide Catalyzed by Polystyrene-Bound Benzyltri-n-butyl-phosphonium Ion, /. ner. Chem Soc., 103,3821 (1981). 

Reactions of benzylic phosphonium salts were carried out at 20 °C using 10 mL of methylene chloride, 1.5 mmol of the polymeric phosphonium salt, and 3 mL of 50% NaOH (aq). The linear polystyrene had a MW of 150,000 with 2.7 mmol of -PPh2/g of polymer. The cross-linked polystyrene contained 3.0-3.5 mmol of -PPh2/g of polymer. The halogenated phosphonium ion was prepared from phos-phinated polystyrene having 0.4 mequiv of -PPh2/g of polymer and was allowed to react with para-tolualdehyde at 50 C for 16 h. 

Kanazawa and co-workers investigated the dependency upon counteranions of poly[tribntyl(4- vinylbenzyl)phosphonium] salts against Staphylococcus aureus it was shown that the antibacterial activity was dependent npon the counteranion structure [9]. The counteranion activity was low when a tight ion-pair with a phosphonium ion was formed, whereas the activity was high for those counteranions liberating free ions. The antimicrobial characteristics, which were governed by the solubility products of the polymers, were in the following order chloride > tetraflouride > perchlorate > hexaflnorophosphate. 

Another highly selective polyaddition is based on the reaction between phenols and oxazolines, which was applied for the synthesis of hb poly(etheramide)s (3-10). The AB2-monomer 2-(3,5-dihydroxyphenyl)-l,3-oxazoline was polymerized thermally at 190 °C in N-methylcaprolactam solution and randomly branched products with a DB of 50% were obtained.Kakodawa et al. used monomer 3-14, namely 2,2-bis(hydroxymethyl) propyl acrylate, for the synthesis of poly(ether ester)s via triphenylphosphine catalysis. The polymers had only low molecular weight, but as they contain phosphonium ions they can be applied in flame-retardant coatings, which can be cured by UV. These materials can also be synthesized via an A2+Bs-approach [vide infra) of tri(acryloy-loxyethyl) phosphate in the presence of piperidine." ... 

By GPC it was shown that all phosphorus detected in the raw polymer was either bound to the polymer as a phosphonium ion or existed as cation 2. Polymer-bound phosphorus was detected only at high temperatures or high concentrations of phosphine (as initiator). This was taken as evidence against the zwitterion mechanism. However, a more detailed look at the data given in Ref. [759] reveals that reactions of the following type could not be excluded (Figure 10). 

MECHANISMS OF CATALYSIS BY POLYMER-SUPPORTED QUATERNARY AMMONIUM AND PHOSPHONIUM IONS... 

Quaternary ammonium and phosphonium ions bound to insoluble polystyrene present an even more complicated mechanistic problem. Polystyrene beads lacking onium ions (or crown ethers, cryptands, or other polar functional groups) have no catalytic activity. The onium ions are distributed throughout the polymer matrix in most catalysts. The reactive anion must be transferred from the aqueous phase to the polymer, where it exists as the counter ion in an anion exchange resin, and the organic reactant must be transferred from the external organic phase into the polymer to meet the anion. In principle, catalysis could occur only at the surface of the polymer beads, but kinetic evidence supports catalysis within the beads for most nucleophilic displacement reactions and for alkylation of phenylacetonitrile. 

The major disadvantages of the polymer-supported quaternary ammonium and phosphonium ion catalysts are 1) They have higher initial cost. Unless they can be used in a flow system or recovered from batch reactors and reused many times, they will be more expensive to use than soluble catalysts. 2) In most cases the insoluble catalysts are less active than their soluble analogues. Their lesser activity is an intrinsic property of heterogeneous catalysts. If activity is the sole criterion for choice of a catalyst, one should use a soluble catalyst. The reasons for use of supported catalysts are ease of separation and reuse. 

Stable indefinitely in polymer-bound catalysts under phase transfer conditions that require the presence of hydroxide ion at the ion exchange site. Benzyltrialkylammonium and phosphonium ions are much less stable in base than non-benzylic tetraalkylammonium and phosphonium ions. Industrial applications of polystyrene-supported onium ion catalysts under strongly basic conditions will require catalysts such as 7, 1 rather than the usual commercially available... 

Organic Cations The organic cations, whose dilute solution can be used in wellbore treatments to minimize polymer plugging, constitute a large class of compounds. They have two common characters a cationic end group and some hydrocarbon substitution on the cation. The cation can be an ammonium ion, a phosphonium ion, pyridinum ion, sulfonium ion, chromium ion or oxonium ion. The hydrocarbon substitution in the case of an ammonium ion can be primary, secondary, tertiary or quaternary. The number of carbons must be smaller than 10 for anionic polymers. When the carbon number is too large, the organic cation precipitates with an anionic polymer such as 30% hydrolyzed polyacrylamide. 

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