Boron trifluoride etherate polymerization

The most important reaction with Lewis acids such as boron trifluoride etherate is polymerization (Scheme 30) (72MI50601). Other Lewis acids have been used SnCL, Bu 2A1C1, Bu sAl, Et2Zn, SO3, PFs, TiCU, AICI3, Pd(II) and Pt(II) salts. Trialkylaluminum, dialkylzinc and other alkyl metal initiators may partially hydrolyze to catalyze the polymerization by an anionic mechanism rather than the cationic one illustrated in Scheme 30. Cyclic dimers and trimers are often products of cationic polymerization reactions, and desulfurization of the monomer may occur. Polymerization of optically active thiiranes yields optically active polymers (75MI50600). 

Kawakami, Suzuki and Yamashita showed that compound 7, among many others, could be polymerized to derivatives of the corresponding open-chained species by treatment with boron trifluoride ether complex. Yamashita and Kawakami formed these same sorts of materials by heating the glycols and paraformaldehyde in the presence of toluenesulfonic acid. This led to prepolymers which were then thermally depolymerized to afford the cyclic oligomers which were separated by fractional distillation. 

Cationic polymerization of cyclic acetals generally involves equilibrium between monomer and polymer. The equilibrium nature of the cationic polymerization of 2 was ascertained by depolymerization experiments Methylene chloride solutions of the polymer ([P]0 = 1.76 and 1.71 base-mol/1) containing a catalytic amount of boron trifluoride etherate were allowed to stand for several days at 0 °C to give 2 which was in equilibrium with its polymer. The equilibrium concentrations ([M]e = 0.47 and 0.46 mol/1) were in excellent agreement with that found in the polymerization experiments under the same conditions. The thermodynamic parameters for the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentrations between -20 and 30 °C. 

The polymerization of 1,3,3-trimethyl-2,7-dioxabicyclo[2.2.1 Jheptane 35 was carried out in methylene chloride, toluene, and 1-nitropropane at temperatures between —78 and 0 °C32l Boron trifluoride etherate, triethyloxonium tetrafluoro-borate, antimony pentachloride, and iodine were used as initiators. Irrespective of the solvents and initiators employed, the products obtained at 0 °C were white powders with melting points of 50—55 °C, while those obtained at tower temperatures were sirups. The number average molecular weight of the unfractionated products ranged from 400 to 600. The molecular weight distribution of the oligomers prepared at 0 °C was broad, in contrast to the relatively narrow distribution of those obtained at -40 °C. 

Tamura etal.2 described only briefly in their paper on dihydropyran derivatives that 6,8-dioxabicyclo[3.2.1]octan-7-one 53 and its methyl derivative underwent polymerization in the presence of a large amount of boron trifluoride etherate to give polymers with molecular weights of several hundreds. 

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

Which of the following could be used to initiate the polymerization of isobutylene (a) sulfuric acid, (b) boron trifluoride etherate, (c) water, or (d) butyllithium ... 

Boron trifluoride etherate is used as a catalyst in many organic reactions namely, alkylation, polymerization and condensation reactions. 

At low temperatures in inert solvents (such as methylene dichloride) a controlled polymerization can be effected using various acids and alkylating agents. These initiators include boron trifluoride etherate, triethylaluminum, trityl hexachloroantimonate, triethylam-monium hexachloroantimonate, diethyloxonium hexafluoroantimonate, p-toluenesulfonic acid and diethylzinc or cadmium-1,2-dioI complexes. Crystalline, high molecular weight... 

Radiation-induced polymerization of crystalline tetroxocane gives a highly crystalline linear polymer in essentially 100% yield (63MI51900,68MI51901), and this has attracted some industrial attention. Tetroxocane also gives a crystalline polymer very rapidly under cationic conditions (boron trifluoride etherate catalyst) and the kinetics of the process have been studied <76MI51900>. 

The synthesis of AMO involves treatment of 3,3-bis(chloromethyl) oxetane (BCMO) with sodium azide in the DMF medium at 85 °C for 24 h. Similarly, AMMO which is a monofunctional analog of AMO is synthesized by the azidation of chloro/tosylate product of 3-hydroxymethyl-3-methyl oxetane (HyMMO) with sodium azide in DMF medium at elevated temperatures. These energetic monomers are readily polymerized to liquid curable prepolymers with the help of boron trifluoride etherate/l,4-butanediol initiator system and the outlines of synthesis [147-150] of poly(BAMO) [Structure... 

In the search for a reactive functional group which could be substituted on the acetylacetonate ring, chloromethylation of these chelates was attempted. The initially formed products were too reactive to be characterized directly. Treatment of rhodium acetylacetonate with chloromethyl methyl ether in the presence of boron trifluoride etherate afforded a solution of a very reactive species, apparently the chloromethyl chelate (XXX) (26). Hydrolytic workup of this intermediate yielded a polymeric mixture of rhodium chelates, but these did not contain chlorine On the basis of evidence discussed later on electrophilic cleavage of carbon from metal chelate rings and on the basis of their NMR spectra, these polymers may be of the type shown below. Reaction of the intermediate with dry ethanol afforded an impure chelate which is apparently the trisethyl ether (XXXI). Treatment of the reactive intermediate with other nucleophiles gave intractable mixtures. 

The first polymerizations reported by Kops and Schuerch147 were those of l,4-anhydro-2,3,6-tri-0-methyl-/3-D-galactopyranose and 1,4-anhydro-2,3-di-0-methyl-a -L-arabinopyranose. The latter compound was slightly contaminated with l,4-anhydro-2,3-di-0-methyl-a-D-xy-lopyranose, but the course of the polymerization could nevertheless be monitored reasonably accurately. For the most part, the polymerizations were conducted at 10% concentration (g/mL) in dichloro-methane, or aromatic hydrocarbons, with 1-5 mol% of phosphorus pentafluoride, or boron trifluoride etherate. At low temperature (—78 to —97°), the d.p. of both polymers produced was —90 at increasing temperatures of polymerization, termination processes became more severe, and the d.p. lower. Usually, the reaction times were long (perhaps unnecessarily so), and the conversions were 50 to 90%. The specific rotations of the D-galactans prepared at —28 and —90° differ by only —10° ( — 85 to — 95°), but those of the L-arabinans varied from + 6... 

Fig. 1. Field effects on rate of polymerization, o styrene-boron trifluoride etherate-1,2-dichloroethane. A a-methylstyrene-iodine-nitrobenzene. Reproduced, with permission, from Ise and Havashi Kobunshi 15, 957 (1966)...

Fig. 3. Polymerization rate and initial initiator concentration styrene-boron trifluoride etherate-l,2-dichloroethane [M]0 = 1.72 mole/1, 0° C. 0.25 KV/cm, O 0 KV/cm. Reproduced, -with permission, from Sakurada, Ise, and Hayashi ...

In the styrene (MJ-indene (Mz) system, rx increased with the field. This result shows that the dissociation of ion pairs at the growing chain ends, the terminal group of which is styrene, was enhanced by the field. As was mentioned above, the field has no effect on the homopolymerization of styrene by boron trifluoride etherate in nitrobenzene (see Fig. 5). This result of the homopolymerization seems to be inconsistent with that obtained for the copolymerization, but can be accounted for as follows. The field-accelerating effect decreases as kp/kp decreases, when an enhancement of the degree of dissociation with the electric field is given. The fact that no field effect was observed on the homopolymerization of styrene with boron trifluoride etherate in nitrobenzene may be attributed to a fairly small value of kp/kp, in addition to the factor af 1. On the other hand, the field enhanced the polymerization of indene by boron trifluoride etherate in nitrobenzene (16). The difference in the field effects of the two monomer systems suggests that the following relation must hold, ... 

Sakurada, I., Y. Tanaka, and N. Ise Cationic polymerization of a-methylstyrene catalyzed by boron trifluoride etherate in 1,2-dichloroethans under an electric field. J. Polymer Sci. A-l 6, 1463 (1968). 

Sakurada, 1., N. Ise, Y. Hayashi, and M. Nakao Ionic polymerization of indene catalyzed by boron trifluoride etherate. Kobunshi Kagaku 25, 41 (1968). 

Korshak and his colleagues reported210 that polymerization of tri-O-methyllevoglucosan with boron trifluoride etherate in dichloromethane gives products having the highest reduced viscosity. The yield of polymer increased with temperature, and the reduced viscosity reached a maximum at -20°. In contrast to tri-O-methylcellulose, poly(tri-0-methyl-D-glu-coses) prepared in this way are insoluble in water, acetone, or ether, but are soluble in chloroform and a cresol. These workers concluded that the products are crystalline and unbranched. 

Rozenberg et al. (24) have also studied the kinetics of polymerization of THF initiated by triethyl oxonium tetrafluoroborate. They generated their catalyst in situ from epichlorohydrin and the boron trifluoride-ether cofnplex and carried out their polymerizations in bulk and in... 

Condensation polymerization of functional ferrocenes generally yields medium- or low-molecular-weight polymers with broad molecular-weight distributions.12 For example, ferrocenylcarbinol, 6.9, has been condensation-polymerized to polymers 6.10 and 6.11 in the presence of boron trifluoride etherate or zinc chloride (reaction (5)).910 Species 6.11... 

Compared with 49, 2,5-dioxabicyclo[2.2.2]octan-3-one (54) prepared from sodium 3,4-dihydro-2//-pyran-2-carboxylate has a much low polymerization reactivity [54] Lewis acids such as antimony pentachloride, phosphorus pentafluoride, and boron trifluoride etherate were not effective at all to initiate the polymerization of 54. Trifluoromethanesulfonic acid induced the polymerization of 54, but the yield and molecular weight of the polymer were low. Bicyclic lactone 54 was allowed to polymerize with anionic and coordination initiators such as butyl-lithium, lithiumbenzophenone ketyl, and tetraisopropyl titanate. However, the... 

Cationic polymerization of 3,9-dibenzyl-1,5,7, ll-tetraoxaspiro[5.5]undecane (123) with tri-phenylmethylcarbenium tetrafluoroborate or boron trifluoride etherate proceeded at room temperature. After the complete consumption of the monomer, the polymerization took place again when the monomer was added to the reaction system. This fact strongly indicates the presence of a stable and long-lived propagating chain end (124) in the polymerization of 123. 

Cationic polymerization of norbomene spiro orthocarbonate (125) differs from that of other spiro orthocarbonates in that it gives a structurally complicated polymer. [102] When polymerized with boron trifluoride etherate at 100 °C in chlorobenzene for 24 h, the 1H NMR of a polymer of 125 showed very reduced olefinic proton signals (22% of the original monomer). The monomer was... 

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