Precipitation from tetrahydrofuran

The novolac sample, which was provided by Kodak, was synthesized from pure meta-cresol and formaldehyde. It has a weight average molecular weight of 13,000 and a very broad polydispersity of 8.5. The polymer was purified by two precipitations from tetrahydrofuran into hexane. The PAC was a naphthoquinone-1,2-(diazide-2-)-5-sulfonyl ester provided by Fairmount Chemical (Positive Sensitizer 1010). A hydroxyl substituted benzophenone is attached to the sulfonyl ester. The spreading solvent was isopropyl acetate, which was obtained from Aldrich Chemicals and used as received. 

Case b In various cases, we observed the formation of large crystals at the bottom of the windowed precipitator. For example, we found large crystals of Prednisolone (corticosteroid) precipitated from Methanol (Figure 1) and of Prednisolone acetate (corticosteroid) precipitated from Tetrahydrofuran, in both cases operating at 150 bar, 40 °C. We also observed that a relative control of the crystal size down to some microns is also possible, in addition to decreasing the concentration in the liquid solution or increasing the ratio between the antisolvent and the liquid solution flow rates. 

Even though this technique has been mostly used with water-soluble polymers, such as PEO, polyvinyl ether (PVE), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA) [134-141], intercalation from nonaqueous solutions has also been reported [142-145]. For example, high-density polyethylene (HDPE)-based nanocomposites have been prepared by dissolving HDPE in a mixture of xylene and benzonitrile with dispersed organomodified layered silicates (OMLSs). The nanocomposite was then recovered by precipitation from tetrahydrofuran (THE) [143], Polystyrene (PS)/OMLS-exfoliated nanocomposites have also been prepared by the solution intercalation technique, by mixing pure PS and organophilic clay with adsorbed cetyl pyrid-ium chloride [146]. Similarly, several studies have focused on the preparation of polylactide (PLA)-layered silicate nanocomposites using intercalation from solution. 

During one run, 48 g. of product precipitated from the tetrahydrofuran reaction mixture. This precipitate was filtered, washed with saturated, aqueous sodium chloride, water, and petroleum ether (b.p. 35-60°) to yield a crystalline product, m.p. 99-106°. For recovery of the remaining product, the tetrahydrofuran filtrate was worked up in accordance with the described procedure. 

The solubility properties of the polymer are very sensitive to the mode of isolation.21 PBPP is partially soluble in tetrahydrofuran immediately after precipitation from the reaction mixture, but when the polymer has been dried the solubility is less predictable. 

Materials. A series of a,to-bis(hydroxyphenyl)PSU oligomers with different molecular weights were synthesized and characterized as was previously reported (12). Two samples of PPO (one from Aldrich and one from General Electric Co.) were both purified by precipitation from chloroform solution into methanol. A commercial sample (Dow Chemical) of an isomeric mixture of chloromethylstyrenes (C1MS, 40% para, 60% meta) was used as received. 1-Chloromethoxy-4-chlorobu-tane (CMCB) was prepared according to a procedure developed by Olah et al. (14) and modified by Daly et al. (15), i.e., from paraformaldehyde, tetrahydrofuran and anhydrous HC1. 

Hamada et al. used a poly (vinyl chloride) matrix membrane ion-selective electrode for the analysis of procaine [76]. Procaine flavianate (10 mg, prepared by precipitation from an equimolar mixture of procaine hydrochloride and flavianic acid), was mixed with PVC powder (150 mg), dioctyl phthalate (370 mg), and tetrahydrofuran (4 mL). This mixture was used to produce membranes (3 cm diameter), from which discs were cut to prepare ion-selective electrodes. The electrodes were used in conjunction with a double-junction Ag-AgCl (KNO3) reference electrode for the potentiometric determination of procaine hydrochloride at 25°C. 

They find that all the groups become bound into the polymer during hot milling but both butyl groups and tin atoms are slowly removed by repeated precipitation in methanol from tetrahydrofuran solution... 

Fig. 2. The effect of repeated precipitation from solution in tetrahydrofuran of samples of pvc which previously had been milled with variously labelled Bu2SnY,...

Benzene is a poor solvent for bisphenol-A oligomers, compared with tetrahydrofuran. At a rather low degree of polymerization, oligomers precipitate from benzene, thus suppressing the chain-building reaction. The GPC curves for benzene-soluble and benzene-insoluble fractions are shown in Figure 7. The benzene-insoluble product contains significantly... 

Figure 3 describes the preparation of A-co-undecenoyl-L-valine CSP bonded to silica gel. The carboxylic acid group of L-valine was protected by the reaction with isobutylene using the method of Roeske [47]. The formed tert-butyl ester of L-valine was precipitated from diethyl ether as the oxalate by the dropwise addition of a solution of 10% oxalic acid in absolute ethanol. The precipitate is dried and the oxalate group is removed by the reaction of sodium hydroxide. The tert-butyl ester of L-valine was treated with undecenoic acid in tetrahydrofuran (THF), which resulted in A-co-undecenoyl-L-valine methyl ester. In another step, lOmM of monochlorosilane was dissolved in 20 mL of dry pyridine and was allowed to react with /V -to - u ndccenoyl-L-valine methyl ester. 

Bis[2,2 -biphenyldiyl] Tellurium3 A solution of 66.4 mmol of 2,2 -dilithiobiphenyl in 250 ml of anhydrous diethyl ether is prepared from 26.9 g (66.4 mmol) of diiodobiphenyl and 132.8 mmol of butyl lithium and cooled to — 70°. 8.17 g (32.5 mmol) of tetramethoxy tellurium are dissolved in 300 ml of anhydrous diethyl ether and this solution is added dropwise to the cooled, stirred solution of 2.2 -dilithiobiphenyl. The resultant mixture is allowed to warm to 20° and is then heated under reflux for 60 h. The mixture is cooled to — 15° and unreacted lithium compound is destroyed by addition of methanol. The precipitate is collected, washed with water and then with diethyl ether yield 6.9 g (49%) m.p. 205-213° (dec. from tetrahydrofuran). 

Coal Alkylation with Butyl-1- C Iodide. Potassium (26.1 mmol) was added to a stirred solution of naphthalene (3.14 mmol) in tetrahydrofuran (45 mL) under argon. After 45 min, -325 mesh coal (1.00 g) and an additional wash quantity of tetrahydrofuran (10 mL) were added. The mixture was stirred for 5 days. The excess potassium (2.98 mmol) was removed. A small quantity of insoluble coal (0.041 g) was unavoidably lost in the removal of the metal. A solution of 90%-enriched butyl-1- C iodide (6.88 g) in tetrahydrofuran (10 mL) was added to the stirred solution in 15 min. This quantity corresponds to a twofold excess of the amount of reagent needed for the alkylation of a coal polyanion with 21 negative charges per 100 carbon atoms and naphthalene dianion. Potassium iodide began to precipitate from the reaction mixture almost immediately. The alkylation reaction was allowed to proceed for 2 days. Potassium iodide rapidly settled from the reaction mixture when stirring was interrupted. 

The alkylation reactions of the coal polyanions also were investigated. The reactions of the polyanion with methyl, butyl, and octyl iodide were compared in tetrahydrofuran. The reaction could be monitored quite readily by the rate at which potassium iodide precipitated from solution. We estimate that methyl iodide is at least fivefold more reactive than butyl or octyl iodide under these conditions. This result, of course, suggests that the Sj 2 reactions of the coal polyanion are more... 

M0S2 catalysts active in hds and hdm of heavy oils have been prepared in suspension by in situ sulphiding of dissolved Mo complexes (acetylace-tonate, naphthenate ). Unsupported sulphides prepared and used in suspension may have advantages in hds and hdm of residual oils and coal-derived liquids where deactivation of conventional supported catalysts by pore plugging of the support is a problem. Amorphous M0S2 may also be prepared by precipitation from M0Q4 and Li2S in tetrahydrofuran. ... 

Poly(V-vinylcarbazole) [25067-59-8]. Precipitate it seven times from tetrahydrofuran with MeOH, with... 

Polystyrene was prepared from freshly distilled and degassed styrene by bulk polymerization at 50° C.imder nitrogen with benzoyl peroxide as the initiator Conversion was about 50%. After precipitation with methanol, the polymer was purified by two reprecipitations from tetrahydrofuran solution with methanol, exhaustively extracted with metha- 1, and finally vacuum-dried at room temperature. The polymer had Mv = 1.8 X 105. Films of this material were prepared from methylene chloride solution in the same way as the PMMA films. 

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