Aqueous Dimethylformamide DMF

Methacrylonitrile can also be determined if acrylonitrile is absent. Both styrene and acrylonitrile can also be determined in acrylonitrile-butadiene-styrene terpolymers, using the same procedure. Tetrabutylammonium iodide (0.1 M TBAI) in aqueous dimethylformamide (DMF) was used as the base electrolyte and polarography was carried out using a differential cathode ray polarograph. 

The separation of aqueous dimethylformamide (DMF) solutions has been studied over the concentration range of 0 to 100 wt%, using sodium alginate (NaAlg)/PVP blend membranes [41]. By adding PVP, the permeation flux was increased while the separation factor decreases. An increase in operating temperature was also found to increase the permeation flux, but to decrease the separation factor. A blend ratio of 75/25 (NaAlg/PVP, w/w) was preferred for the remainder of the study, due to acceptable flux and separation factors. When Aminabhavi and Naik... 

The idea is to have everything in place before the oxygen is applied. So, lOOg of safrole is in the addition funnel and stirring around in the reaction flask are 10.6g of PdCU, 60g CuCI and 500mL of aqueous dimethylformamide (made by mixing 62.5mL dH20 and 437,5mL DMF). Dimethylformamide (DMF) is not the same as the watched chemical known as N-methylformamide. 

Samal et al. [25] reported that Ce(IV) ion coupled with an amide, such as thioacetamide, succinamide, acetamide, and formamide, could initiate acrylonitrile (AN) polymerization in aqueous solution. Feng et al. [3] for the first time thoroughly investigated the structural effect of amide on AAM polymerization using Ce(IV) ion, ceric ammonium nitrate (CAN) as an initiator. They found that only acetanilide (AA) and formanilide (FA) promote the polymerization and remarkably enhance Rp. The others such as formamide, N,N-dimethylformamide (DMF), N-butylacetamide, and N-cyclohexylacetamide only slightly affect the rate of polymerization. This can be shown by the relative rate (/ r), i.e., the rate of AAM polymerization initiated with ceric ion-amide divided by the rate of polymerization initiated with ceric ion alone. Rr for CAN-anilide system is approximately 2.5, and the others range from 1.04-1.11. 

Coelenterazine emits chemiluminescence when dissolved in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) containing a trace amount of base. It also emits bioluminescence in aqueous media in the presence of a coelenterazine luciferase, such as Renilla luciferase or Oplophorus luciferase. In both cases, the luminescence reactions require molecular oxygen. The capability of coelenterazine to produce luminescence is attributed to the presence of the imida-zopyrazinone structure in the molecule. 

The process of copolymerization of AN with 4 has been studied in aqueous solution (in suspension), in emulsion, and in dimethylformamide (DMF) solution3, l9. ... 

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). 

A. (S)-Ethyl 2-(t-Butyldimethylsilyloxy)propanoate (1). A 2-L, two-necked, round-bottomed flask equipped with a mechanical stirrer and inert gas inlet (Note 1) is charged with (S)-ethyl lactate (118 g, 1.0 mol), 500 mL of dimethylformamide (DMF), and imidazole (102 g, 1.5 mol) (Note 2). The solution is cooled in a ice bath and te/ t-butyldimethy 1 si 1 y 1 chloride (TBDMSC1) (150 g, 1.0 mol) is added in three 50-g portions, at intervals of 30 min between each addition. After the addition of the third portion, a white precipitate forms. The ice bath allowed to melt gradually overnight. After 18 hr, the reaction mixture is diluted with 300 mL of water and 500 mL of hexanes. The aqueous phase is separated and extracted with 300 mL of hexanes, and the combined hexane extracts are washed with three 50-mL portions of saturated brine, dried over MgS04, filtered, and concentrated by rotary evaporation to afford 240 g (103%) of the TBDMS ether as a colorless liquid. The product is distilled under vacuum (bp 70-78°C, 0.5 mm bath temperature 95-105°C) (Note 3) to afford 222 g (96%) of ester 1 as a colorless liquid (Notes 4, 5). 

Researchers studying polypeptide and polypeptide hybrid systems have also processed vesicles using two solvents. This method usually involves a common organic solvent that solubilizes both blocks and an aqueous solvent that solublizes only the hydrophilic block. The two solvents can be mixed with the polypeptide or polypeptide hybrid system at the same time or added sequentially. The choice of organic solvent depends heavily upon the properties of the polypeptide material, and commonly used solvents include dimethylformamide (DMF) [46, 59], methanol (MeOH) [49], dimethyl sulfoxide (DMSO) [50, 72], and tetrahydrofuran (THF) [44, 55]. Vesicles are usually formed when the organic solvent is slowly replaced with an aqueous solution via dialysis or removed through evaporation however, some vesicles have been reported to be present in the organic/aqueous mixture [49]. 

ABNP is soluble in dimethylformamide (DMF) but insoluble directly in aqueous solution. Insulin labeling was done in DMF water at a ratio of 9 1. For molecules not soluble in organic solvent, such as proteins, the trifunctional first may be dissolved in DMF and a small aliquot added to an aqueous reaction medium. The nitrophenyl ester reactive group can be coupled to amine groups at alkaline pFI (7-9) and in buffers containing no extraneous amines (avoid Tris). Unfortunately, ABNP is not commercially available at the time of this writing. 

Ethyl a-bromobutyrate (58.5 g., 0.30 mole) (Note 1) is poured into a stirred mixture of 600 ml. of N,N-dimethylformamide (DMF) (Note 1), 36 g. of sodium nitrite (0.52 mole) (Note 1), and 40 g. of anhydrous phloroglucinol (0.32 mole) (Note 2) contained in a 1-1. three-necked flask equipped with a sealed stirrer. The flask is closed, except for a tube containing calcium chloride, and immersed in a water bath maintained at room temperature (Note 3). Stirring is continued for 2.5 hours (Note 4) then the reaction mixture is poured into 1.2 1. of ice water layered over with 300 ml. of diethyl ether (Note 5). After separation of the upper layer, the aqueous phase is extracted with four 100-ml. portions of ether. The combined extracts are washed with four 100-ml. portions of water and then dried over anhydrous magnesium sulfate. The magnesium sulfate is removed by suction filtration and washed with four 25-ml. portions of ether which are combined with the filtered extract. 

The first microscopical computation of a free energy curve for a chemical reaction in solution was performed by the Jorgensen s group [41,52,53] ten years ago. They studied the degenerate SN2 reaction of chloride anion with methyl chloride in gas phase, in aqueous solution and in dimethylformamide (DMF) ... 

When hexane solutions of the octacarbonyl are treated with an excess of dimethylformamide (DMF) and the resulting mixture is slowly acidified at 0° with 12 N HCl, according to the procedure of Kirch and Orchin (15), the liberated HCo(CO)4 goes into the hexane layer. The bottom aqueous-DMP layer containing CoClg is syringed away from the top layer the top hexane layer is then washed and dried and provides a dilute solution of hydrocarbonyl of known concentration. 

The recent introduction of non-aqueous media extends the applicability of CE. Different selectivity, enhanced efficiency, reduced analysis time, lower Joule heating, and better solubility or stability of some compounds in organic solvent than in water are the main reasons for the success of non-aqueous capillary electrophoresis (NACE). Several solvent properties must be considered in selecting the appropriate separation medium (see Chapter 2) dielectric constant, viscosity, dissociation constant, polarity, autoprotolysis constant, electrical conductivity, volatility, and solvation ability. Commonly used solvents in NACE separations include acetonitrile (ACN) short-chain alcohols such as methanol (MeOH), ethanol (EtOH), isopropanol (i-PrOH) amides [formamide (FA), N-methylformamide (NMF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA)] and dimethylsulfoxide (DMSO). Since NACE—UV may present a lack of sensitivity due to the strong UV absorbance of some solvents at low wavelengths (e.g., formamides), the on-line coupling of NACE... 

Silver-Silver Ion Electrode This is the most popular reference electrode used in non-aqueous solutions. Since Pleskov employed it in acetonitrile (AN) in 1948, it has been used in a variety of solvents. It has a structure as shown in Fig. 6.1(a) and is easy to construct. Its potential is usually reproducible within 5 mV, if it is prepared freshly using pure solvent and electrolyte. The stability of the potential, however, is not always good enough. The potential is stable in AN, because Ag+ is strongly solvated in it. In propylene carbonate (PC) and nitromethane (NM), however, Ag+ is solvated only weakly and the potential is easily influenced by the presence of trace water and other impurities. In dimethylformamide (DMF), on the other hand, Ag+ is slowly reduced to Ag°, causing a gradual potential shift to the negative direction.2) This shift can reach several tens of millivolts after a few days. 

The progress of the reaction can be monitored by TLC by working up a sample of the reaction mixture filter through Celite, cool to 0°C, and acidify to pH 1 with 10% aqueous HCI. The solid that precipitates is isolated by filtration and dissolved in dimethylformamide (DMF) for TLC analysis on Merck precoated-silica gel 60 plates with methyl ethyl ketone-methanol-water (4 1 1) as eluent, developed by dipping in 5% sulfuric acid-ethanol and heated to 450°C (e.g., with a Bunsen burner). Rf values are 0.25 for fl-cyclodextrin, 0.5 for monotosylate and 0.65 for a second product, probably ditosylate. 

To a suspension of sodium hydride (0.48 g, 20 mmol) in N,Al-dimethylformamide (DMF 20 mL) at — 5°C under nitrogen water (0.18 mL, 10 mmol) in 5 mL of DMF was added, followed by a larger portion of 5 and 6 (3.6 g, 9.1 mmol). After 2 h, a solution of benzyl bromide (2.38 mL, 20 mmol) in dry DMF (20 mL) was added and the mixture was left at room temperature. After 24 h, ethanol (2 mL) was added and the mixture was poured into aqueous saturated ammonium chloride solution (100 mL). The product was extracted with ethyl acetate, the extracts were dried (MgS04) and concentrated to dryness. The residue was purified by chromatography on silica gel column using toluene-ethyl acetate (9 1) for elution to yield 7 and 8 (3.37 g, 83%). 

Fe2(SR)2(CO)6], which are readily available from the reactions of R2S2 with [Fe3(CO)12] (33) and of RSH with [Fe2(CO)9] (34), can be nitrosylated in reactions which replace three carbonyl ligands by two nitrosyl ligands. Nitrosylation can be effected either by use of nitric oxide gas (27,29) or by use of sodium nitrite in aqueous ethanol (27) or, better, in dimethylformamide (DMF) (25). It is usually more convenient to employ nitric oxide if complexes of normal isotopic composition are required, but for 15N labeling the use of sodium nitrite in DMF is the more convenient and economical route. 

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