Dimethyl sulfoxide and dimethylformamide

All three polymers possess high molecular weights in the range of 20-25,000 by gel permeation chromatography. They are soluble in polar solvents such as dimethylacetamide, dimethyl sulfoxide, and dimethylformamide, and insoluble in non-polar solvents such as chloroform and... 

The product is a very pale yellow to cream-colored solid. It is hygroscopic and is soluble in liquid ammonia, with limited solubility and stability in acetonitrile, dimethyl sulfoxide, and dimethylformamide. Water or moisture from the air leads to disproportionation, and so the product must be stored under anhydrous... 

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

Another interesting reaction of benzoxazines 114 (115) is the reductive opening of the oxazine ring with simultaneous dehydrogenation of the pyrazoline moiety [170]. This process is carried out in a KOH suspension of a mixture of dimethyl sulfoxide and dimethylformamide. For instance, this treatment involving 2,5-diary l-l,10b-dihydro-177-pyrazolo[l,5-c]benzo[e]-l,3-oxazines 116 leads to the formation of pyrazoles 117 (Scheme 2.32). Similar disproportionation reactions have also been described for some bezopiranes, for example, pyrazole derivative 118 [91, 170]. 

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... 

Dimethyl sulfate-Barium oxide, see also Methyl iodide. Dimethyl sulfate in combination with barium oxide or barium hydroxide, Ba(0H)j-8H20, provides an effective method for the perraethylation of carbohydrates. Dimethyl sulfate is cheaper and sometimes superior to methyl iodide. Dimethylformamide is the usual solvent, but for carbohydrates only slightly soluble in this solvent dimethyl sulfoxide or a mixture of dimethyl sulfoxide and dimethylformamide is used. 

Hexamethylphosphoric triamide [680-3/-9] [14.280] is a basic, highly polar, nonflammable solvent with a very good solvency. Its dissolution properties are comparable to those of dimethyl sulfoxide and dimethylformamide. It is used for selective dissolution of organic compounds, as a reaction medium in chemical syntheses, as an antifreeze, and as an antistatic agent. 

Kinetic parameters have been established for solvolysis of the pentacyanofer-rate(III) derivative [Fe(CN)5(N02)] . For aquation, which is acid-catalyzed at pH <5, A//= = 43kJmol-, =-80 J K" mol", and A =+2 cm" mol". Intrinsic and solvational contributions are presumably closely balanced in the case of A Rate constants for solvolysis of [Fe(CN)5(N02)] in water, methanol, dimethyl sulfoxide, and dimethylformamide correspond with the electron-donating abilities of the respective solvents. Activation volumes for the nonaqueous solvents, between +20 and +27 cm" mor reflect the dissociative nature of these solvoly-ses. " Rate constants for dissociation of the [Fe(CN)5(2,6-Me2pyrazine)]" anion in binary aqueous solvents containing methanol, acetone, or acetonitrile correlate well with acceptor numbers for the respective media, though with a very different... 

A review of liquid atomization by electrical means. J. Aerosol Sci., 25, 1005-1019 (b) Szabo, P.T. and Kele, Z. (2001) Eiectrospray mass spectrometry of hydrophobic compounds using dimethyl sulfoxide and dimethylformamide as solvents. Rapid Comm. Mass Spectrom., 15, 2415-2419 (c) Henderson, M.A. and Mclndoe, J.S. (2006) Ionic liquids enable eiectrospray ionisation mass spectrometry in hexane. Chem. Commun., 2872-2874. 

Table 7.12 summarizes the results of the reaction of bromobenzenes with activated nickel. Although the reactivity of bromobenzenes toward nickel was relatively lower than that of iodobenzenes, they reacted at 85°C to give biphenyls in moderate to good yields, together with the corresponding reduction products. The reaction of 4-bromochlorobenzene with nickel powder from nickel bromide in glyme afforded chlorobenzene as the major product. Dimethyl sulfoxide and dimethylformamide were tried these solvents did... 

In an independent study, Voronkov and coworkers have reported the preparation of a 1 2 K2S208/18-crown -6 complex characterized as being soluble in methanol, dimethyl sulfoxide, and dimethylformamide. Results obtained using this complex for the polymerization of styrene and methyl methacrylate (MMA) in methanol at 60 C are listed in Table 6. The obviously reduced efficiency of this sytem as compared with results obtained under our conditions certainly can be traced in part to the use of less reactive monomers. However, we can speculate that the choice of solvent, protic vs aprotic, may play a major role as well. 

Analogously to the dissociation of X in [Fe(CN)5(X)] , the oxidation of [FeCCN) ] " to [Fe(CN)g] by O2 in aqueous-organic solvent mixtures depends drastically on the electron-donating abilities of solvents, the reaction in dimethyl sulfoxide and dimethylformamide being about 10 times faster than... 

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