Solvent purification dimethyl sulfoxide

While water has been used as a solvent more than any other media, nonaqueous solvents [e.g., acetonitrile, propylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or methanol] have also frequently been used. Mixed solvents may also be considered for certain applications. Double-distilled water is adequate for most work in aqueous media. Triple-distilled water is often required when trace (stripping) analysis is concerned. Organic solvents often require drying or purification procedures. These and other solvent-related considerations have been reviewed by Mann (3). 

N-Bromosuccinimide purchased from Arapahoe Chemical Company was used without purification. If the purity of the N-bromosuccinimide is in doubt, it should be titrated before use by the standard iodide-thiosulfate method and purified, if necessary, by recrystallization from 10 times its weight of water. Solutions of N-bromosuccinimide in dimethyl sulfoxide cannot be stored, since the solvent is oxidized by the brominating reagent. 

The parent hexathiaadamantane (185) is obtained preparatively when a solution of formic acid and hydrochloric acid in nitrobenzene is allowed to stand for several weeks in a hydrogen sulfide atmosphere the product which separated is almost insoluble in all common solvents and purification presents a problem. Only large volumes of dimethyl sulfoxide at reflux serve for recrystallization.224 The reaction of thioacetic acid with formic acid in the presence of zinc chloride gives tetramethyl-(186), monomethyl-, dimethyl-and trimethylhexathiaadamantane derivatives (187).225 Other variations include the reaction of thioacetic acid with a /i-diketone,226 and the use of boron trifluoride227 or aluminum chloride as a catalyst.228... 

Materials. Reagent grade solvents, dimethyl formamide (DMF), dimethyl acetamide (DMAC), dimethyl sulfoxide (DMSO) and methanol were purchased from Baker, stored over molecular sieves once opened, and used without further purification. Aminoethane thiosulfuric acid (AETSA) purchased from Kodak, and Taurine, purchased from Alfa were purified by recrystallization. Each was thrice recrystallized from hot, deionized water. The crystalline precipitate was dried (48 hours at 40 °C) in-vacuo and subsequently stored in a desiccator. Benzophenone (BP) was purchased from Aldrich Chemical Company. QUANTACURE BTC (BTC), (4-benzolybenzyl) trimethylammonium chloride, was used as supplied by Aceto, Inc., Flushing, New York. Phenyl glycidyl ether (PGE) was purchased from MCB, distilled in-vacuo. and stored at -15 °C. Epon 828 was used as supplied bv Shell Chemical Company. The epoxy equivalent weight (EEW) for Epon 828 determined by an appropriate titration, was found to be 187.7. 

Dimethyl sulfoxide (DMSO) [14] Commercial products contain water and small amounts of dimethyl sulfide and dimethyl sulfone as impurities. In the purification, molecular sieve 5A (activated at 500 °C under argon for 16 h) is added and kept for several days to reduce water to < 10 ppm and other low boiling point impurities to < 50 ppm. Then the solvent is filtered and the filtrate is distilled over CaH2 at reduced pressure in a nitrogen atmosphere. 

A number of companies supply reagent or spectroquality solvents that have been purified to remove UV-absorbing impurities. Some of them, particularly dimethyl sulfoxide, may be suitable for general electrochemical use as purchased. However, small quantities of electroactive impurities (particularly water) often are present in spectroquality solvents. Therefore, a particular batch of solvent always should be tested by measurement of the residual current with an appropriate supporting electrolyte and a platinum, gold, or carbon electrode (to test the anodic limits) and a platinum electrode (to test the cathodic limits). The voltage window or domain of electroactivity is a sensitive measure of the adequacy of the purification procedures. 

Although a number of solvents have been used by different workers, only a few enjoy continued favor. In Table 7.11 the physical properties of more than 50 solvents are listed (not all of them are aptotic). In the following paragraphs some of the properties and purification methods for four solvents are discussed acetonitrile, propylene carbonate (PC), dimethylformamide (DMF), and dimethyl sulfoxide (Me2SO). These are the most widely used solvents and prob-... 

Although somewhat difficult to purify, acetonitrile is stable on storage after purification. It is toxic, with a maximum recommended limit of 40 ppm,79 and the vapor pressure is sufficient for this to be a hazard. Its high volatility makes the removal of solvent by evaporation easy (e.g., workup of a reaction mixture for product identification). Both radical cations and anions react with traces of wate r in acetonitrile, and, because it does not hydrogen-bond to water as do dimethyl sulfoxide and dimethylformamide, radical anions generally have a... 

The reagent-grade solvent generally contains few impurities beyond traces of water and can be used without further purification for many electrochemical purposes. For some applications the presence of traces of water can significantly affect the properties of the solvent. For example, dimethyl sulfoxide and dimethylformamide that contain 100 ppm of water dissolve NaCN and NaN3 to... 

J. F. Coetzee (ed.) Recommended Methods for the Purification of Solvents and Tests for Impurities, Pergamon Press, Oxford, 1982. (Acetonitrile, Sulfolane, Propylene carbonate. Dimethyl sulfoxide, V,7V-Dimethylformamide, Hexamethylphosphoric tiiamide. Pyridine, 1,2-Diaminoethane, N-Methylacetamide, and V-Methylpropionamide). 

Isoquinoline [119-65-3] M 129.2, m 24 , 25.5-26 , h 120 /18mm, 243.25 /760mm, d " 1.0986, Ud 1.6148, pK 5.40. Dry isoquinoline with Linde type 5A molecular sieves or Na2S04 and fractionally distil at reduced pressure. Alternatively, it can be refluxed with, and distilled from, BaO. It is also purified by fractional crystallisation from the melt and distilled from zinc dust. It forms a phosphate (m 135 ) and a picrate (m 223°), which are purified by crystallisation, and the free base can be recovered and distilled. [Packer et al. J Am Chem Soc 80 905 795S.] The procedure for purification via the picrate comprises the addition of quinoline to picric acid dissolved in the minimum volume of 95% EtOH to yield yellow crystals which are washed with EtOH and air dried before recrystaUising from acetonitrile. The crystals are dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through a basic alumina column, on which picric acid is adsorbed. The free base in the effluent is extracted with -pentane and distilled under vacuum. Traces of solvent from small quantities are removed by vapour phase chromatography. The hydrochloride crystallises from EtOH with m 193°. [Mooman Anton J Phys Chem 80 2243 1976, Beilstein 20 II 236, 20 III/IV 3410, 20/7 V 333.]... 

BaA and BaP is added and the entire sample is extracted with methylene chloride (250-, 100-, and 100-mL portions). The extracts are combined, 10 mL of isooctane added, and the solution evaporated to about 10 mL. When the solution approaches 10 mL, a second 10-mL volume of isooctane is added. This is repeated three times. The isooctane solution is made up to 75 mL and extracted with three 100-mL portions of dimethyl sulfoxide (DMSO) that contains 20% phosphoric acid. The DMSO extracts are each washed with three 30-mL portions of fresh isooctane, combined and diluted with 500 mL of water. This solution is extracted with three 80-mL portions of isooctane. The isooctane extracts are combined, rinsed once with water, and evaporated to 25 mL. At this point, a 1-mL portion of the solution is removed for intermediate radioassay and a UV scan. Usually the concentrate is sufficiently free from interferences and is evaporated down to about 0.05 mL and an aliquot injected into the GC. If further purification is indicated, the solution is chromatographed on a 1.1-cm X 90-cm column containing 75 g of Woelm Neutral Alumina deactivated with 2% water. Before deactivation, the alumina is dried in an oven for 1 hr at 150°C. The solvent elution schedule is as follows 25 mL cyclohexane prewash, 25-mL sample in cyclohexane, 100 mL cyclohexane, 100 mL cyclohexane-methylene chloride (9 1), 100 mL cyclohexane-methylene chloride (1 1), 100 mL methylene chloride. After the first 125 mL has eluted, 10 cuts are then radioassayed and combined into a single PNA fraction. This fraction is evaporated to about 0.05 mL in preparation for the GC-UV finishing step. Figure 2 is a diagram of the wastewater procedure. 

In Fry and Britton s handy review of solvents and electrolytes, acetonitrile, ethanol, methanol, and methylene chloride are recommended as good oxidative (anodic) electrochemical solvents, while acetonitrile, DMF, and dimethyl sulfoxide (DMSO) are suggested for reductive (cathodic) electrochemistry. Acetonitrile is suggested as the best overall nonaqueous solvent on the basis of its electrochemical properties and its relative nontoxicity. The review of Fry and Britton also is a good place to start when looking for purification methods. 

The practical applications of fluoropolymer membranes especially in the areas of purification and separation related to potable water production, wastewater treatment and bioprocessing, have been limited to some extent by their hydrophobic and inert surface properties. Among the different modification techniques, graft copolymerization of hydrophilic monomers, or inimers for further surface reactions, from fiuoropolymers has been useful and effective in improving the physicochemical properties of the parent fluoropolymer with minimum alteration of their desirable bulk properties. Apart from fiilly fluorinated polymers, most of the partially fluorinated polymers can dissolve in polar organic solvents, such as Ai,Ai-dimethylformamide (DMF), A,A-dimethylacetamide (DMAc), NMP, and dimethyl sulfoxide (DMSO), but are insoluble in water, alcohols, and hydrocarbons. 

Benzaldehyde (9, 318 mg, 3 mmol) was dissolved in a mixture of dimethyl sulfoxide (20 mL) and potassium phosphate buffer [80 mL, 50 mM, pH 7.0, containing MgS04 (2.5 mM) and ThDP (0.15 mM)]. After addition of BAL (20 U) the reaction mixture was allowed to stand at 25 °C for 48 h before a further 20 U of BAL were added. After 62 h no more benzaldehyde was detected (GC-MS). The reaction mixture was extracted with dichloromethane (250 mL) and the organic layer washed with water (25 mL) and brine (25 mL) and dried over Na2S04. Evaporation of the solvent and purification of the crude product by crystallization afforded (/ )-2-hydroxy-l,2-diphenyl-ethan-l-one ((l )-10) as a colorless solid yield 305 mg (96%, 99% ee). 

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