DMSO solvent

Institut Eransais du Pntrole dimethyl sulfoxide (DMSO) solvent contains up to 2% water to improve selectivity reflux con-sist of aromatics and paraffins ambient rotating-blade extractor, typically 10—12 stages low corrosion allows use of carbon steel equipment solvent has alow freezing point and is non-toxic two-stage ex-traction has dis-placement solvent in the second stage... 

In order to avoid as far as possible double bond positional isomers, a problem quite common in drugs with indene moieties, N-trityl-2-hydroxymethylmorpholine (23) was reacted with the potassium. salt of 4-hydroxy-1-indanone (24) in DMSO solvent to give condensation product 25 in good yield. Reduction of 25 with LLAIH produced the hydroxyindane which was dehydrated and deprotected with HCl to give indeloxazine (26) [8]. 

Treatment of dimethylsulfoxide (DMSO) with sodium hydride generates methylsulfinyl carbanion (dimsyl ion), which acts as an efficient base in the production of ylides. The Wittig reaction appears to proceed more readily in the DMSO solvent, and yields are generally improved over the reaction with -butyl lithium (i). Examples of this modification are given. 

Procedure To a dry Erlenmeyer flask of appropriate size, add one half of the reaction solvent. All reactants, including the dry mass of the hydroperoxide, should not constitute more than 23 weight percent of the reaction mixture or an insoluble product may be produced. Add dry lignin and dry calcium chloride to the reaction vessel and cap with a septum or rubber stopper. In a separate vessel, dissolve 2-propenamide in about one quarter of the DMSO solvent and, in a third vessel, dissolve the sulfonated monomer in the final one quarter of the solvent. Saturate both monomer solutions with by bubbling with the gas for 10 minutes. Saturate the lignin solution with for 10 minutes. Add the hydroperoxide to... 

The electrodeposited Bi2Sr2CaiCu2Ox (BSCCO) precursor films were obtained by co-electrodeposition of the constituent metals using nitrate salts dissolved in DMSO solvent. The electrodeposition was performed in a closed-cell configuration at room temperature ( 24°C). The cation ratios of the electrodeposition bath were adjusted systematically to obtain BSCCO precursor compositions. A typical electrolyte-bath composition for the BSCCO films consisted of 2.0-g Bi(N03)3-5H20,1.0-g Sr(N03)2, 0.6-g Ca(N03)2-4H20, and 0.9-g Cu(N03)2-6H20 dissolved in 400 mL of DMSO solvent. The substrates were single-crystal LAO coated with 300 A of Ag. 

In the case of benzotriazole compounds which display both absorption bands, the observed spectrum consists of the superposition of the individual spectra that correspond to the two distinct ground-state species. The absorption spectrum of TIN in methanol/dimethylsulfoxide (DMSO) solvent mixtures varies with the composition of the solvent (Figure 5) in a manner which suggests that the proportion of planar and non-planar forms of TIN is solvent dependent. 

Figure 7. Plot of mole percent of TIN(non-planar) and < )fnP versus mole percent of methanol for methanol/DMSO solvent mixtures.

In methanol/DMSO solvent mixtures the fluorescence spectrum of TIN (A.max = 400 nm) displays a normal Stokes shift indicating that this emission arises from a non proton-transferred, excited state of TIN. The fluorescence excitation spectrum for this emission coincides with the absorption spectrum of the resolved non-planar species suggesting that this conformer is the ground-state precursor responsible for the observed emission. As the amount of DMSO in the mixture increases the fluorescence maximum undergoes a bathochromic shift from 415 nm in pure methanol to 440 nm in pure DMSO. 

Figure 4 reveals a similar pattern for acidities in DMSO solvent versus the gas phase. Once again, the small, localized anions result in solution acidities that are relatively stronger than the gas phase counterparts. The acids with large... 

Figure 4. Gas phase acidities versus acidities in DMSO solvent. Data from Refs. 6, 27, and 64. Both axes in kcal/mol. Open squares = carboxylic acids. Open triangles = phenols. The straight line is a least-squares fit to primary alcohol acidities. CpH = cyclopentad iene.

In solution, lithium hexamethyldisilazide (LiHMDS) is a strong enough base to deprotonate esters, ketones, and alcohols, with a pK of about 27 in DMSO solvent. In the gas phase, the bare anion is too weak to deprotonate methanethiol, much less the ketones, esters, and comparable carbon acids. The change in relative anionic basicity is on the order of 14 kcal/mol. 

Figure 2. Views of the structures of 1 (a) and 2 (b). The coordination polymers are shown in ball and stick mode, zinc ions are shown in polyhedra, DMSO solvent molecules are shown in CPK mode.

Benzphetamine demethylase stimulation. Methyl chloride extract of the leaf, administered intragastrically to rats at a dose of 3 mg/animal daily for 21 months in DMSO solvent, was active. The rats were... 

GST inhibition. Methyl chloride extract of the leaf, administered intragastrically to rats at a dose of 3 mg/animal daily for 21 months in DMSO solvent, was active. The rats were divided into two groups one was fed a vitamin A diet, and the other a vitamin A-defi-cient diet. In the vitamin-deficient group, the treatment decreased GST levels in liver and lung vs control and vitamin-fed groups . 

If the water content is driven off (usually by heating to 350 °C in a vacuum), the dehydrated zeolite becomes an avid absorber of small molecules, especially water. The size of the molecules that can be absorbed is limited by the zeolite pore diameter, which is different for different zeolites (Table 7.1) a given zeolite (e.g., zeolite 3A) can be a highly selective absorber of, say, small amounts of water from dimethyl sulfoxide (DMSO) solvent. For this reason, dehydrated zeolites are often called molecular sieves. 

Thus, N-pyrimidine phthalimide reacted with hexylamine at room temperature to form an amide-amide. The initial amide-amide formation proceeded more rapidly in chloroform as compared to dimethylsulfoxide (DM SO). However, the ring closure reaction to the imide was favored by the more polar, aprotic DMSO solvent, yielding the imide in nearly quantitative yield after 3 hours at 75 °C. The authors were able to utilize this synthetic approach to prepare well-defined segmented poly(imide-siloxane) block copolymers. It appears that transimidi-zation reactions are a viable approach to preparing polyimides, given that the final polyimide has a Tg sufficiently low to allow extended excursions above the Tg to facilitate reaction without thermal decomposition. Additionally, soluble polyimides can be readily prepared by this approach. Ultimately, high Tg, insoluble polyimides are still only accessable via traditional soluble precursor routes. 

Preparation The dimsyl anion is generated from dimethylsulfoxide (DMSO) by use of base. The resulting lithio- or sodio- derivative is generally used in the DMSO solvent. 

The cleavage of 4-nitrophenyl acetate by [Co(NH3)5OH]2+ and [Co(NH3)5Im]2+ (Im = N-deprotonated imidazole) has been studied in water and DMSO solvents.192 All the reactions are exclusively nucleophilic as demonstrated by the detection of the acetylated products [(NH3)sCo02CMe]2+ and [(NH3)5CoImCoMe]3+. Typical kinetic data are summarized in Table 18. The large difference in the reactivity of the two complexes towards 4-nitrophenyl acetate is closely paralleled by their differences in basicity. In Me2SO the complexes have a similar reactivity towards the ester (fcMIm = 30M 1 s 1, k OH = 0.72 M"1 s-1 at 25 °C), and this increase is largely due to the marked increase in the basicity of [Co(NH3)5OH]2+ relative to that of [Co(NH3)5Im]2+ in the dipolar aprotic solvent. 

Similar results have been obtained in the reactions of 1 and sodium salts of p-cresol and - and /J-naphthols. Under SN2 conditions (DMF or DMSO solvent), the alkylation of sodium cresolate occurs exclusively at the oxygen atom. The addition of a protic solvent causes C-alkylation, though the yields of C-alkylated products are low. Thus in acetone-water or dioxane-water, the yield of C-alkylated products 251 and 252 increases only up to 2%. C-Alkylation has also been observed in the reactions catalyzed by trifluoroacetic acid or boron trifluoride etherate at room temperature. The observed C-alkylation in protic media may be a reflection of a mechanism that involves a protonated epoxide or a more polarized transition state than in an SN2 pathway. 

The rate of substitution of diethylmercury by hydrogen chloride in DMSO was increased on addition of dioxan and on addition of sodium chloride, but was unaffected by added sodium sulphate. The corresponding substitution of diphenyl-mercury was retarded by the addition of water to the DMSO solvent, and was unaffected by added sulphuric acid. All of these observations indicate28 that the electrophile is undissociated hydrogen chloride (i.e. unionised hydrogen chloride plus ionised but not dissociated hydrogen chloride in other words, covalent... 

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