Methylene chloride, purification

Methyl -propyl ketone, 340 Methyl pyridines, purification of, 177-179 N-Methylpyrrole, 837, 838 Methyl red, 621, 625 sodium salt of, 626 Methyl salicylate, 780,782 Methyl sulphite, 304 2-Methylthiophene, 836 Methyl p-toluenesulphonate, 825 Methylurea, 968, 969 Methylene bromide, 300 Methylene chloride, purification of, 176 3 4-Methylenedioxycinnamic acid, 711, 719... 

The solvent used to form the dope is evaporated during the extrusion process and must be recovered. This is usually done by adsorption on activated carbon or condensation by refrigeration. For final purification, the solvent is distilled. Approximately 3 kg of acetone, over 99%, is recovered per kg of acetate yam produced. Recovery of solvent from triacetate extmsion is similar, but ca 4 kg of methylene chloride solvent is needed per kg of triacetate yam extmded. 

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6]-, 1,1-dichloroethane cis- and /n j -l,2-dichloroethylenes [156-59-2 and 156-60-5]-, 1,1-dichloroethylene [75-35-4] (vinyhdene chloride) 2-chloroethanol [107-07-3]-, ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5])-, and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of soflds which can foul and clog operating lines and controls (78). 

A mixture of 1.38 grams of the above compound and 15 cc of dioxane was treated with 1.9 cc of a 0.5 N aqueous solution of perchloric acid and 600 mg of N-bromoacetamide, adding the latter in the dark, in three portions, in the course of half an hour and under continuous stirring. It was then stirred for a further 1% hours in the dark, then the excess of reagent was decomposed by the addition of aqueous sodium bisulfite solution and ice water was added the product was extracted with methylene chloride, washed with water, dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure, thus giving a yellow oil consisting of the 16,21-diacetate of 6a-fluoro-9a-bromo-16o-hydroxy-hydrocortisone which was used for the next step without further purification. 

Benzothiadiazole 1,1-dioxide can be conveniently assayed and characterized without isolation by forming its adduct with cyclopentadiene.5 The following procedure illustrates characterization, for assay the same procedure can be applied to an aliquot, with all amounts scaled down in proportion. The dried ether extract of 1,2,3-benzothiadiazole 1,1-dioxide prepared from 1.43 g (0.0080 mole) of sodium 2-aminobenzene-sulfinate is concentrated to about 20 ml at 0°, and 20 ml. of acetonitrile at —20° is added. Twenty milliliters of cold, freshly prepared cyclopentadiene6 is added The mixture is kept overnight at —10° to 0°. Solvent and excess cyclopentadiene are removed by evaporation at 0° under reduced pressure to leave 1.20-1.28 g. (64-68% based on sodium 2-aminobenzenesulfinate) of crude 1-1 adduct, mp. 87° (dec.). For purification it is dissolved in 20 ml. of methylene chloride, 70 ml. of ether is added, and the solution is kept at —70°. Adduct decomposing at 90° crystallizes recovery is about 75%. From pure, crystalline 1, 2, 3-benzothiadiazole 1,1-dioxide the yield of adduct is 92-98%. 

An aqueous extract of P. hysterophorus (collected in Puerto Rico) was partitioned into methylene chloride at pH 7, pH 10 and pH 2. Bioassays of the methylene chloride soluble fractions, using the bean second internode bioassay (13), showed that the highest activity was concentrated in the methylene chloride extract at pH 7. Extensive chromatographic purification (flash chromatography, medium pressure LC, preparative TLC) monitored by bioassay led to the isolation of the four sesquiter-... 

The checkers found that the purification of the pseudopelletierine could be simplified, at least in those preparations in which commercial acetonedicarboxylic acid was used. Thus, the crude product obtained by evaporation to dryness of the methylene chloride extracts can be sublimed directly. Two sublimations give pseudopelletierine of m.p. 62-64°, in 58-62% yield, comparable to the product obtained after the more extended purification procedure described in the text. 

Dimethylformamide (DMF), dioxane, piperidine, methylene chloride, acetonitrile, trimethyl orthoformate (TMOF), sodium borohydride, diisopropylcarbodiimide, and trifluoroacetic acid (TFA) were purchased from Aldrich Chemical Company, Inc. and used without further purification. All of the diversity reagents were purchased from Aldrich except for Fmoc-glycine-OH, which was purchased from Novabiochem. 

Available from Aldrich Chemical Co. and used without further purification. Methylene chloride may be substituted for the nitro-methane. The checkers used reagent grade nitromethane available from Tokyo Kasei Kogyo Co. Ltd., Japan. 

Materials The methods used for the purification of aluminium bromide and chloride and for preparing phials of these catalysts, and the purification of methyl bromide, methylene chloride, and ethyl chloride, have been described [9]. The solvents were stored in a vessel coated with a sodium mirror and attached to the vacuum line, and they were metered into the observation cell by distillation from a hanging burette. 

Reagent grade methylene chloride was used without further purification. 

As a model metathesis reaction, diethyl diallyhnalonate was cychzed in the presence of 5 mol% (41) within forty minutes in methylene chloride at 40 °C the product was isolated as a colorless oil after filtration and removal of volatiles. An analogous reaction with the soluble catalyst (29) was complete in less than five minutes, suggesting that metathesis reactions catalyzed by (41) are diffusion-controlled. Nonetheless, a reaction time of forty minutes is reasonable, and the validation for this chemistry lies in the simplified purification procedure and minimization of waste streams. 

Carotenoids A large number of solvents have been used for extraction of carotenoids from vegetables matrices, such as acetone, tetrahydrofuran, n-hexane, pentane, ethanol, methanol, chloroform [427-431], or solvent mixtures such as dichloromethane/methanol, tetrahydrofuran/methanol, -hexane/acetone, or toluene or ethyl acetate [424,432-435], SPE has been used as an additional purification step by some authors [422,426], Supercritical fluid extraction (SEE) has been widely used, as an alternative method, also adding CO2 modifiers (such as methanol, ethanol, -hexane, water, methylene chloride) to increase extraction efficiency [436-438], In addition, saponification can be carried out, but a loss of the total carotenoid content has been observed and, furthermore, direct solvent extraction has been proved to be a valid alternative [439],... 

Sams0e-Petersen et al. [701] used focused MAE to extract PAHs with a mixture of hexane and methylene chloride from fruits and vegetables grown in contaminated soils. A further purification step (often performed by SPE) is always needed before HPLC determination. 

Materials. Styrene (Aldrich) was purified by distillation from CaH2 before use. n-Butyllithium (Aldrich) was used without further purification. Tetrahydrofuran (Fisher Scientific) was purified in a solvent still by distillation from a sodium/benzophenone mixture. Toluene (Fisher Scientific) was used without further purification. Reagent grade methylene chloride (Baker Chemical Co.) was dried on 5A° molecular sieves. Reagent grade triethy-lamine (Baker) was dried over KOH. Methanesulfonyl chloride (Aldrich, 98%) was used without further purification. 

Lyophilized, pulverized leaves (5.35 kg) of S. divinorum were extracted with ether. The nonpolar components were removed from the concentrated extract through partition between hexanes and 90% aqueous methanol. The dried methanolic fraction was crudely purified by silica gel flash column chromatography (hexanes-ethyl acetate 2/1). Further purification of the biologically active fractions by additional silica gel flash column chromatography (methylene chloride-methanol 20/1) followed by repeated recrystallization yielded pure divinorin A (1) (1.2 g) and B (3) 50mg. 

B. Bis(2,4,6-trimethylpyridine)iodine(l) hexafluorophosphate. A 1-L, threenecked, round-bottomed flask equipped with a mechanical stirrer, condenser topped with a drying tube containing calcium chloride, and a stopper is charged with 500 mL of dry methylene chloride (Note 6), 82.5 g of bis(trimethylpyridine)silver(l) hexafluorophosphate (0.166 mol), and 41.9 g of iodine (0.165 mol). The mixture is stirred until all the iodine is consumed (1 hr - 2 hr) (Note 7). The resulting yellow solid (silver iodide) is suction filtered, and washed with 100 mL of dry methylene chloride. The filtrate is concentrated on a rotary evaporator at a maximum bath temperature of 30°C to give 68-76 g (80-88%) of yellowish solid bis(2,4,6-trimethylpyridine)iodine(l) hexafluorophosphate (mp 132-133°C) (Notes 8, 9, and 10). This product is suitable for reactions without further purification. 

Chemicals and Standard Solutions. Cyclohexanone, cyclohexanol, 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, phenol, 4-methylphenol, 4-chloro-phenol, 1,2,3,4-tetrahydroisoquinoline, 1-chlorohexane, 1-chlorododecane, and 1-chlorooctadecane were obtained from Aldrich. Acetone, tetrahydrofuran, ethyl acetate, toluene, dimethyl sulfoxide, and methanol were obtained from J. T. Baker. Distilled-in-glass isooctane, methylene chloride, ethyl ether, and pentane were obtained from Burdick and Jackson. Analytical standard kits from Analabs provided methyl ethyl ketone, isopropyl alcohol, ethanol, methyl isobutyl ketone, tetrachloroethylene, dodecane, dimethylformamide, 1,2-dichlorobenzene, 1-octanol, nitrobenzene, 2,4-dichlorophenol, and 2,5-dichlorophenol. All chemicals obtained from the vendors were of the highest purity available and were used without further purification. High-purity water... 

One of the most comprehensive reviews on solvent use and purification was prepared by C.K. Mann [13]. Many solvents are discussed, and for each particular solvent, suitable supporting electrolytes and reference electrodes are presented. Lund and Iversen [65], among others [66], have also surveyed the use, purification, and properties of solvents. There are overlaps among all of these reviews and the present one, but each has its own special flavor and the different viewpoints make for instructive comparisons. There are also a number of articles devoted to specific solvents, such as DMSO [62,67], DMF [68], methylene chloride [69], and pyridine [70]. 

A multiresidue preparation technique—MSPD—has also been applied to the analysis of CAP residues in meat samples. Two fractions were collected by elution with methylene chloride and ethyl acetate. No additional purification was necessary. Diode assay detection and fluorescence detectors were recommended for the multiresidue analysis of sulfonamides, benzimidazoles, nicarbazin, furazolidone, and CAP. The percentage recoveries and linearity of the method were evaluated. The method was linear from 50 to 250 /tg/kg of CAP. Not only do the authors recommend the MSPD multiresidue procedure for HPLC analysis, but it could be associated with several detection modes, such as immuno- or receptor assays. The MSPD technique represents a new approach in the field of biological-matrix extraction and provides a great possibility for the analysis of a wide range of compounds (20). 

Purification of the crude material is accomplished by dissolving it in petroleum ether (30-50°) or methylene chloride, shaking this solution three times with water, and passing the organic layer through a fluted filter paper After the filtrate has been dried over anhydrous sodium sulfate, it is concentrated to a small volume and cooled to —78°. The perfectly white, crystalline product which separates is collected yielding 110-120 g. (30-33%) of crystals, m.p. 57-58° (Note 4). 

For further purification the product is dissolved in 40 ml. of methylene chloride in a 250-ml. Erlenmeyer flask. The solution is heated to boiling, and 30 ml. of methanol is added (Note 7). When the solution has cooled to room temperature, 70 ml. of methanol is added to complete the crystallization, and the solution is kept in the ice box for 3 hours. The colorless needles are collected by vacuum filtration and washed with two 30-ml. portions of cold methanol. There is obtained 23-25 g. (76-82%) of product which melts at 99-100° (Notes 8-10). 

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