Wurtz reaction type

Another condensation method was investigated by Carothers and co-workers and reported in 1930. They reacted decamethylene dibromide with sodium in a Wurtz-type reaction but found it difficult to obtain polymers with molecular weights above 1300. 

PVC has been shown to have a head-to-tail structure. Typical experimental evidence for this is that when dissolved in dioxan and treated with zinc dust, it undergoes a Wurtz-type reaction to yield a product containing a small amount of chlorine and no detectable unsaturation. The alternative possible structure, the head-to-head arrangement, would yield unsaturated sites where adjacent chlorine atoms had been removed (Reaction 1.4). 

The NaPb-C2HsCl reaction is characterized by an induction period. This induction period can be shortened by the use of various reaction accelerators, such as acetone and other ketones, esters, aldehydes, acid anhydrides, ketals, amides, phosphates, and metal alkoxides 34,50,51,95, 96,246,284), induction period can also be shortened by the substitution of a small amount of potassium for the sodium in the alloy (on an atom basis) such potassium substitution also increases the yield and minimizes Wurtz-type reactions 49,288,289,320). 

Gibian, M. J. and C. Corley, Chem. Revs. (1973), 7, 441. The Complex mixture of products resulting from frei radi-cals in Wurtz-type reactions have been described by J. F. Garst, "Chemically Induced Magnetic Polarization," A. R, Lepley and G. L. Closs, eds., Chapter 6, J. Wiley and Sons, New York, 1973. See also Chapter 7, Ibid., H. R. Ward, R. G. Lawler and R. A. Cooper. 

An alternative route to the formation of the carbanion and the 1,3-elimination process is via a Wurtz-type reaction(equation 23). 

On the other hand, hydrolysis with aqueous alkalis is complete, producing hydrogen and silicates. Silyl iodide gives a Wurtz-type reaction with sodium, wliich affords a useful path to disilane ... 

Without an activator the reaction is assumed to be initiated by a catalytic amount of magnesium halide MgX, resulting from a Wurtz-type reaction, which would, following Kharasch and Reinmuth, account for the disproportionation products as well ... 

The starting materials for the four-, five and six-membered ring systems, Si4Phg, SisPhio, Si6Phn, and SisMesPhs, were synthesised by well-known Wurtz-type reactions (Eqs. 1-2). 

Osborne, A. G., Glass, K. J., Staley, M. L. Ultrasound-promoted coupling of heteroaryl halides in the presence of lithium wire. Novel formation of isomeric bipyridines in a Wurtz-type reaction. Tetrahedron Lett. 1989, 30, 3567-3568. 

The five cyclotetraphosphines t-Bu4 (Me3Si)nP4 ( =0—4) have all been isolated as yellow crystalline solids. The first of the series, though not a Si-P compound, is included for completeness and was the first to be isolated. It results from the Wurtz-type reaction of sodium with t-BuPCl2 in dioxan in 63% yield56. It is also formed from the partial chlorination of r-BuP(SiMe3)2 (44) by hexachloroethane to give the first characterisable... 

OTHER COMMENTS used as a solvent for waxes, oils, fats, gums, perfumes, and alkaloids an excellent solvent for nitrocellulose when mixed with alcohol useful in organic syntheses, especially as a reagent in Grignard and Wurtz type reactions used in the production of drugs of abuse, in the manufacture of gun powder, and as a primer for gasoline engines applications as an extractant of hormones, etc. from plant and animal tissues has also been used as an anesthetic. 

Riedel et al. have appUed the hydroboration reaction for modifying polymethylvinylsilanes with several borane adducts. The polymethylvinyl-silane polymers were synthesized by a dechlorination reaction (Wurtz type reaction) of dichlorodimethylsilane and dichloromethylvinylsilane with sodium. The subsequent hydroboration of the vinyl groups has resulted in an enhanced crosslinking of the polymers. The viscosity of the polyorganosilanes can be tuned by varying the amount of borane as well as of vinyl groups in the starting polymer [61]. 

Palladium-catalyzed germylation of 2,5-dibromothiophene using (ClMe2Ge)2 has been reported. The monomer on Wurtz type reaction with sodium leads to the polymer <92CL647>. 

Although several improvements have been effected in the basic Wurtz-type reaction it must be mentioned that there is still not a single universal synthetic protocol that allows a high yield, monomodal, high-molecular-weight polysilane synthesis. For every new system that needs investigation, the optimum reaction conditions have to be experimentally determined. 

No yields were reported in the following Wurtz-type reaction ... 

Polyisobutylene of low molecular weight was synthesized by a Wurtz type reaction from l,4-dibromo-2,2,3,3 tetramethylbutane. Polyacrylates were obtained from alternating copolymerization of symmetric internal olefins or ethylene with maleic anhydride followed by quantitative esterification. Poly(vinyl halides) were prepared from cis-1,4-polybutadiene by chlorination (H-H PVC) or bromin-ation (H-H PrBr). The polymers were characterized and their chemical, thermal, degradation solution, melt and blending behavior was studied. 

The polymer used in this study was produced by a Wurtz-type reaction, and was purified by reprecipitation to separate the high molecular weight portion (M v = 1.2 x lO by GPC). Films approx. 2.5 jun thick were prepared on quartz substrates by conventional spinning techniques using a 2% solution (by weight) of the polymer in isooctane. The films were subsequently baked in an oven at lOO C to remove the residual solvent, and cooled in a reftigerator to facilitate recrystallization. 

Shizuka et al " and Wildeman et al. have reported that the Wurtz-type reaction may also be used to prepare alternating copolymers as in the coupling of diorganolithium compounds (6) with dihalosilanes (7) (Scheme 2). The product (8) of the reaction in this case forms a liquid crystalline, mesophase material that exhibits o-jt conjugation. 

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