Tetrahydrofuran-water 50 mass

As a part of the continuing studies of the effect of dipolar aprotic solvent plus water mixtures on these specific solute-solvent interactions, we have examined the first and second dissociation steps of glycine and computed their associated thermodynamic quantities in 10 mass % tetrahydrofuran-water (THF-H20) solvents (dielectric constant, c = 71.8 at 298.15 K), 30 mass % THF-H20 (c — 56.6 at 298.15 K), and 50 mass % THF-H20 (c — 40.0 at 298.15 K) from 278.15 to 328.15 K. 

Table VII. The pKi, pK2, cr, and a0 of Protonated Glycine (GIT and G ) in 10 Mass Percent Tetrahydrofuran-Water from 278.15 to 328.15 K on the Molal Scale...

G ) in 50 Mass Percent Tetrahydrofuran—Water from 278.15 to 328.15 K on the Molal Scale... 

Table XIII. Thermodynamic Functions (on the Mole-Fraction Scale) for the Dissociations of Glycine in 10 Mass Percent Tetrahydrofuran—Water at Temperatures (T) from 278.15 to 318.15 K...

Ballesteros-Gomez A, Rubio S, van Leeuwen S. Tetrahydrofuran-water extraction, inline clean-up and selective liquid chromatography/tandem mass spectrometry for the... 

The general reaction procedure and apparatus used are exactly as described in Procedure 2. Ammonia (465 ml) is distilled into a 2-liter reaction flask and to this is added 165mlofisopropylalcoholandasolutionof30g(0.195 mole) of 17/ -estradiol 3-methyl ether (mp 118.5-120°) in 180 ml of tetrahydrofuran. The steroid is only partially soluble in the mixture. A 5 g portion of sodium (26 g, 1.13 g-atoms total) is added to the stirred mixture and the solid dissolves in the light blue solution within several min. As additional metal is added, the mixture becomes dark blue and a solid (matted needles) separates. Stirring is inefficient for a few minutes until the mass of crystals breaks down. All of the sodium is consumed after 1 hr and 120 ml of methanol is then added to the mixture with care. The product is isolated as in Procedure 4h 2. After being air-dried, the solid weighs 32.5 g (ca. 100% for a monohydrate). A sample of the material is dried for analysis and analyzed as described in Procedure 2 enol ether, 91% unreduced aromatics, 0.3%. The crude product may be crystallized from acetone-water or preferably from hexane. 

These three polymeric HALS stabilisers can be detected and positively identified in extracts from polyolefins using an Agilent Ion-trap instrument with positive APCI. Figure 34 shows a chromatogram for a 5-ppm standard of Tinuvin 622 in tetrahydrofuran (THF) and the peak mass spectrum (Figure 35). Similar data for Chimassorb 944 in THF are shown in Figures 36 and 37, respectively. A Waters Xterra C8 150 x 2.00 mm 3 pm 125A column at 60°C with the mobile phase of isopropanol +700 pl/1 hexylamine was employed. 

TLC coupled with mass spectrometry employing desorption electrospray ionization has been used for the separation of synthetic dyes. The chemical structures of dyes included in the investigation are shown in Fig. 3.7. ODS HPTLC plates (10 X 10 cm) were used as the stationary phase the mobile phase consisted of methanol-tetrahydrofuran (60 40, v/v) containing 50-100 mM ammonium acetate for the positive-ion test and of methanol-water (70 30, v/v) for the negative-ion test. Test mixtures for negative- and positive-ion mode detection consisted of methyleneblue, crystal violet, rhodamine 6G... 

The FD mass spectra provide qualitative distribution of various species in HTE polymers. Most importantly, the spectra also provide the structural information to prove the incorporation of one unit of modifier, ethylene glycol or water, in HTE polymers. This is also the first analysis that distinguishes HTE polymers synthesized in conjunction with ethylene glycol and water. The incorporation of one unit of modifier into the polymer chain has been estimated semi-quantitatively with H NMR method for the copolymerization of tetrahydrofuran and propylene oxide in conjunction with 1,4-butanediol as a modifier (7). 

A potentiometric method for determination of ionization constants for weak acids and bases in mixed solvents and for determination of solubility product constants in mixed solvents is described. The method utilizes glass electrodes, is rapid and convenient, and gives results in agreement with corresponding values from the literature. After describing the experimental details of the method, we present results of its application to three types of ionization equilibria. These results include a study of the thermodynamics of ionization of acetic acid, benzoic acid, phenol, water, and silver chloride in aqueous mixtures of acetone, tetrahydrofuran, and ethanol. The solvent compositions in these studies were varied from 0 to ca. 70 mass % nonaqueous component, and measurements were made at several temperatures between 10° and 40°C. 

The investigations mentioned so far aimed at objectives of rather low molar mass. Reversed-phase chromatography of polystyrenes with 17,500 and 50,000 g/mol was performed on C 18 columns with water/tetrahydrofuran gradients or mixtures3). The latter sample was isocratically eluted from 30 nm-pore packing with 85 % THF as a broad band, 87 % THF let the polymer elute in the void volume, whereas 83 % did not produce an observable band at all. 

Because C02 has weak dissolving capabilities, it is suitable as an extraction medium in SFE only for compounds of small and medium molecular mass and of low polarity. As a result, suitable modifiers must be added in order to extract polar substances. Modifiers are polar organic solvents, that is, with a nonzero dipole moment (methanol, acetonitrile, tetrahydrofuran, or water are the most commonly used) that enhance the diffusibility of polar analytes in nonpolar extraction media such as C02. 

Polyesterurethanes, polycarbonate and silicone rubbers have been studied by TG-Tenax-FTIR/MS. The degradation of polyesterurethanes yields C02, water, tetrahydrofurans, cyclopentanone, dicarbonic acid, and aliphatic diols and esters. The thermal decomposition of silicone rubbers leads to the formation of polychlorinated biphenyls which are produced in small amounts and can be observed in the mass spectrometer [86]. 

Acetone-Pis an unstable, white powder or crystalline mass with a melting point of 90 to 93 Celsius. The solid is insoluble in water, but soluble in ether and tetrahydrofuran. It is quite unstable and is rarely used in military or commercial explosives. However it can be utilized as a primary explosive in blasting caps or detonators when desensitized with appropriate materials. To do so, it should be mixed with gum Arabic, carbon black, tri sodium phosphate, chalk, or silicon dioxide powder, and then mixed with a small amount of paraffin s or saturated oils prior to use. Acetone-P can also be slurried with 10% water and 5% hexane for use in blasting caps or detonators. Pure acetone-P should not be used by itself, as it will decay over time potentially leading to explosions. Acetone-P is rather volatile, and a small sample left out in the open will completely evaporate after several days—partly due to decomposition. Acetone-P can also be used in initiating compositions when mixed with sulfur nitride or other primary explosives, and then added to a small amount of a saturated oil. The sulfur nitride and other primary explosives can be replaced by bari urn chromate, copper perchlorate, or lead chromate. Even when acetone-P has been successfully desensitized, it should be used withi n 2 weeks of preparation. ... 

Three solvent systems were used System 1,10% acetonitrile (Baker UV spec grade), 4% alcohol (Baker HPLC grade alcohol, 95% ethanol, 5% methanol), and 2% tetrahydrofuran (Aldrich gold label) in 0.01 M aqueous acetic acid System 2, 7% acetonitrile, 8% alcohol, and 5% tetrahydrofuran in 0.01 M aqueous acetic acid and System 3, 30% aqueous acetonitrile. The water used was distilled double-deionized water (Millipore MilliQ system, type 1 water, Bedford, Mass.) degassed by boiling. Once prepared, the solvent system was filtered through a Millipore Durapore membrane 0.45-/um filter. 

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