Precipitation from toluene

All monomers (Petrarch) used in this study were carefully fractionally distilled prior to use. The condensation polymerization was carried out at approximately 110°C and allowed to reflux for 4 hours after the addition of the sodium metal was completed. The high molecular weight copolymers were obtained after two precipitations from toluene into ethyl acetate. 

In an effort to quantify the effect of photolysis, polysilanes 2 and 8 were selected as typical models. For this experiment, samples of 2 were fractionated by repeated precipitation from toluene using isopropanol. No additional... 

EPDM with different contents of 5-ethylidene-2-norbornene (VISTALON 7500 (VIST), EXXON, 0.7 mol. kg 1 POLYSAR 585, (POLY) HOECHST, 1.0 mol. kg 1) and polyoctenamer (VESTENAMER, (VEST) HULS, 9.1 mol. kg 1) were first precipitated from toluene solutions to remove possible additives. 

Hydride polyaddition of divinyl-containing compounds was carried out for various lengths of a,co-dihydridedimethylsiloxanes. The reaction run was searched by a decrease of active =Si-H groups concentration. It was found that for rhodium acetylacetonatedicarbonyl as a catalyst, copolymers soluble in organic solvents were obtained, which were structured after some time. This may be explained by the fact that in spite of polymers re-precipitated from toluene solution by methyl alcohol, rhodium catalyst remains in polymeric systems, which decompose and induce structuring (cross-linking) of copolymers. 

After over-precipitation from toluene solution with methyl alcohol, the oligomers synthesized repre-sent solid products with T Spec=0.05-1.0. It is shown that at short length of linear diphenylsiloxane unit, n<2, oligomers completely soluble in various organic solvents are obtained. The yield of solu-ble part of oligomers is decreased with the length increase, n. 

When precipitated from toluene solution with methanol, synthesized copolymers are solid or viscous substances with r spec = 0.07-0.30, well soluble in usual organic diluters, with regard to dimethylsi-loxane unit value. Table 14 shows the yield, Tg and viscosity parameters of cyclolinear carbosilo-xane copolymers. 

Equivalent Weights. The equivalent weights of the salts precipitated from toluene solution were determined by titration with sodium hydroxide. Some difficulty was encountered in finding a suitable solvent for the titrations, but two methods were developed for obtaining reproducible titration results. 

Alkylation of pseudoephedrine sarcosinamide can be used to prepare enantiomerically enriched A -methyl-a-amino acids. Anhydrous pseudoephedrine sarcosinamide has been prepared by the addition of sarcosine methyl ester to a mixture of pseudoephedrine, lithium chloride, and lithium methoxide. In contrast to the preparation of pseudoephedrine glycinamide, the amount of dipeptide by-product produced in the reaction is minimal, perhaps due to the increased steric hindrance of the N-methyl group of sarcosine. Thus, pure anhydrous pseudoephedrine sarcosinamide can be obtained from the crude acylation reaction mixture by precipitation from toluene and subsequent drying. Like anhydrous pseudoephedrine glycinamide, anhydrous pseudoephedrine sarcosinamide can be handled in the atmosphere for brief periods without consequence, but should be stored with scrupulous avoidance of moisture to prevent hydration. 

Purification the hydrochloride salt can be precipitated from toluene solution, and the free base is dissolved in heptane upon treatment with NaOH. Concentration and cooling of the cold heptane solution affords the crystalline solid. 

Poly(dichlorophenylene oxide) and a conducting polymer have been simultaneously obtained from 2,4,6-trichlorophenol by Cakmak et al. (Scheme 14.38) [75]. Micro vave-initiated polymerization was performed in a Pyrex vessel in which 2.5 g 2,4,6-trichlorophenol was mixed with 0.5 g NaOH and 1-2 mL triple-distilled water. The reaction mixtures were irradiated in a domestic microwave oven for times from 1 to 7 min. The resulting polymers, i.e. poly(dichlorophenylene oxides) and the conducting polymer (0.3 S cm ), were separated by precipitation from toluene. The optimum conditions for poly(dichlorophenylene oxide) and the conducting polymer were 70 W for 5 min and 100 W for 1 min, respectively. 

Precipitation from toluene at room temperature yields samples with only one transition at 285-286 K upon heating (type A). These samples are sticky solids at room temperature, in agreement with their low phase-transition temperatures. Type A is probably the type of material that most authors have obtained and investigated. Its Si MAS spectra below the transition temperature show one major peak at 8 = -28.5 ppm together with a much smaller peak at 5 = -20.8 ppm. These peaks disappear simultaneously at the transition to the mesophase whether or not they belong to one structure is not clear. The chemical shift value of the smaller peak indicates a transoid structure similar to that of PD6S. 

Fullerene C70 does not form a complex with the same calixarene in toluene, but it does so in benzene, crystallizing as the 2 1 complex, (C7o)2(p-Bu -calix[8]arene) (structme unknown).The same fullerene also forms a 2 1 complex with / -Bu -calix[6]arene, and its precipitation from toluene solutions can be used to retrieve 87% purity C70 from Ceo-depleted fullerite. 

Isolated yield after precipitation from toluene. 

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