DMSO/ethanol mixtures

Structural Effects and Solvent. The effect of solvent on the equilibrium of Reaction 4 can be first discussed in terms of effects on the susceptibility to substituent effects. The values of pK2, characterizing this equilibrium, are a satisfactorily linear function of the Hammett constants correlation coefficient r (Table VI). The values of reaction constant p are practically independent of the ethanol concentration (Table VI), as was already indicated by the almost constant value of the difference (A) between pK2(H20) and p 2 (mixed solvent) for a given composition of the mixed solvent (Table I). The same situation is indicated for DMSO mixtures (Table II) by the small variations in A for any given solvent composition. In this case, the number of accessible p 2 values was too small to allow a meaningful determination of reaction constants p. The structural dependence for various water-ethanol mixtures is thus represented by a set of parallel lines. The shifts between these lines are given by the differences between the pK2H values (p 2 of Reaction 4 for the unsubstituted benzaldehyde) in the different solvent mixtures. 

Ni et al. (2002) studied the stability of SarCNU (NSC 364432) in water, ethanol, propylene glycol (PG), Capmul PG, and DMSO, as well as their combinations over the temperature range of 25-660. The two cosolvents are an 80% PG 20% ethanol mixture (PE), and a semiaqueous vehicle (WPE) containing 50% water 40% PG 10% ethanol. The degradation mechanism in all the studied solvents is the same, and the stabilization by these vehicles follows the order of Capmul PG > Ethanol > PE > PE > PG > WPE > water, which is in agreement with their decreasing polarities. 

A mixture consisting of the Step 2 product (200mg), l,3-bis(diphenylphosphino) propane (8.7 mg), and Pd(OAc)2 (4.7 mg) was placed under a carbon monoxide atmosphere, then treated with 0.2 ml 2-(trimethylsilyl)ethanol, 0.12 ml triethylamine, and 0.9 ml DMSO. The mixture was stirred 3 hours at 70°C and was then extracted with CH2C12. It was washed with 1M HC1, then purified by flash chromatography using EtOAc/petroleum ether, 5 95 to 10 90, and the product isolated in 91% yield, mp = 205°C. 

A Schlenk apparatus was charged with the briefly sonicated Step 1 product dispersed in DMSO and treated with the drop wise addition of 10 ml of a lOmM solution of Wilkinson s complex in DMSO. The reaction mixture was stirred at 55°C to 60°C for 80 hours and filtered through a 0.2 pm nylon membrane. Dissolved tubes were precipitated out by treating the solution with saturated brine. The precipitated material was purified by filtering over a 0.2 pm nylon membrane and washing in DMSO, ethanol, and water. 

Acetone or acetonitrile are commonly used as solvents to extract TNT from soils, although a mixture of DMSO/Ethanol was used as a solvent to extract TNT in a report on toxicity studies [8], These colorimetric methods can be used to detect a class of explosives, such as nitroaromatics, nitramines, and nitrate esters. However, explosives within a class cannot be distinguished very well. The most preferred on-site method relies on colorimetric detection as explained in the EPA Method 8515 for TNT. These methods require manual sample extraction for soil samples and preconcentration for water samples. Further, calibration with a control solution needs to be performed manually, the sample and reagents have to be mixed manually, and the absorbance from a spectrophotometer is noted manually. 

Figure 16.5. Snapshots of the simulation of different binary mixtures - water-DMSO in the top panel, water-ethanol in the middle, and water-TBA in the bottom panel. Water molecules are shown in silver. Co-solvents (DMSO, ethanol, and TBA) are represented in blue. The snapshot is shown at two different concentrations - one before the onset of percolation to show the microheterogeneity in the system, and one after the onset of percolation to show the spanning cluster of the cosolvent. Figure adapted with permission from/. Phys. Chem. B, 115 (2011), 685. Copyright (2011) American Chemical Society. See plate section for color version.

Amorphous Nanoparticles of Amoxicillin Using SAS technology, Kalogiannis et al. produced amorphous nanoparticles of amoxicillin. The crystalline drug was dissolved in dimethysulfoxide (DMSO), or mixtures of DMSO with ethanol or methanol. Partially replacing the DMSO with ethanol or methanol further helped to reduce the particle size (Kalogiannis et al. 2005). 

Some kinetic data are available for reactions of chromium(m) in methanol-water and in DMSO-water mixtures, and for (dissociative) replacement of water by DMSO in [Cr(N03)(0H2)5l + in water-DMSO mixtures. Kinetic results for reaction of /ra 5-[Co(dmgH)2(OaSC6H4Me)(solvent)] with pyridine or with triphenylphosphine in water, methanol, ethanol, and water-methanol mixtures are more easily accommodated by a Z> than by an /d mechanism. ... 

If the purpose of an evaluation of mutagenicity of a complex mixture is to ascertain whether activity is present, it may suffice to use a simple extraction method. The extraction can be designed to remove and concentrate organics in general or to perform a preliminary separation in preparation for the isolation of specific classes of compounds. Organic solvents of choice are dimethyl-sulfoxide (DMSO), ethanol, benzene, methylene chloride, hexane, methanol, isopropanol, cyclohexane, or combinations of various solvents. Examples of such extraction procedures utilized as environmental bioassays of potential mutagens (carcinogens ) contained on or within particulate matter have been... 

Figure 8. Change of swelling coefficients Kg of crosslinked poly-N-vinylcaprolactam in chloroform-ethanol (1), chroloform-dioxane (2) and chloroform-DMSO (3) mixtures.

Mixed-solvent solutions of various cosolvent-water proportions are titrated and psKa (the apparent pKa) is measured in each mixture. The aqueous pKa is deduced by extrapolation of the psKa values to zero cosolvent. This technique was first used by Mizutani in 1925 [181-183]. Many examples may be cited of pKa estimated by extrapolation in mixtures of methanol [119,161,162,191,192,196,200], ethanol [184,188-190,193], propanol [209], DMSO [212,215], dimethylformamide [222], acetone [221], and dioxane [216]. Plots of psKa versus weight percent organic solvent, Rw = 0 — 60 wt%, at times show either a hockey-stick or a bow shape [119]. For Rw > 60 wt%, S-shaped curves are sometimes observed. (Generally, psKa values from titrations with Rw > 60 wt% are not suitable for extrapolation to zero cosolvent because KC1 and other ion pairing interferes significantly in the reduced dielectric medium [223].)... 

Water was used as the catalyst phase for the palladiiun complex of TPPTS and toluene or an excess of the substrate anihne served as the non-polar product phase. To determine an appropriate solvent system cloud titrations were performed at 90 °C, 60 °C, 40 °C and 25 °C. A solution of 4-chloro-nitroben-zene in aniline and water were mixed in a weight ratio of 1 1 and semi-polar solvents were added as a mediator until a homogeneous solution was formed. As the mediator the following solvents were apphed methanol, ethanol, isopropyl alcohol, n-butanol, DMF, DMSO, ethylene glycol, N-methylpyrrohdone (NMP), 1.4-dioxane and acetonitrile. The cloud titrations were repeated whereby the substrate 4-chloro-nitrobenzene was replaced with the product 4-nitrodiphenylamine. In all cases more of the semi-polar mediator is required for the product mixture at 25 °C than for the reaction mixture at 60 °C to obtain a clear solution. 

With ethanol and DMSO as mediators catalysis experiments were performed. By use of DMSO, about 70% of the product can be obtained, if the reaction takes place in one single phase in a two-phase system the yield decreases to about 30%. With ethanol almost no product can be detected, because a biphasic system was formed with this solvent under all conditions. In all cases the inorganic components K2CO3 and KCl were insoluble in the reaction mixture. 

The cadmium electrodeposition on the cadmium electrode from water-ethanol [222, 223], water-DMSO [224], and water-acetonitrile mixtures [225-229] was studied intensively. It was found that promotion of Cd(II) electrodeposition [222] was caused by the formation of unstable solvates of Cd(II) ions with adsorbed alcohol molecules or by interaction with adsorbed perchlorate anions. In the presence of 1 anions, the formation of activated Cd(II)-I complex in adsorbed layer accelerated the electrode reaction [223]. 

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