Dimethylsulphoxide, solvent

Further evidence to support the theory that slow rates of proton transfer to carbanions are due to the need to reshape the solvation shell is given by the observation that these rates are much faster in solvents which only weakly solvate anions. Dimethylsulphoxide is such a solvent [36], since the negative end of its dipole is located on a single oxygen atom whereas the positive end is delocalised over the methyl groups. For example, the rate of deprotonation, as followed by racemisation, of 2-methyl-3-phenylpropionitrile by methoxide ion in methanol is accelerated by the admixture of dimethylsulphoxide to the solvent, and extrapolation to pure dimethylsulphoxide solvent suggests that the rate would... 

DMSO - Dimethylsulphoxide is a very common solvent with a freezing point of 20 degrees. When you buy this stuff it will be crystallised in the bottle. To melt, all you need to do is place the bottle in a bowl of hot water for 30 minutes - simple. If you re lucky enough to live somewhere warm it may already be liquid, where I live, no chance. When you open the bottle you will notice that this stuff smells a bit farty, don t worry too much, it doesn t get that bad. 500ml straight into the reaction flask and start the stirrer. 

Dissolution/reprecipitation processes were evaluated for the recycling of poly-epsilon-caprolactam (PA6) and polyhexamethyleneadipamide (PA66). The process involved solution of the polyamide in an appropriate solvent, precipitation by the addition of a non-solvent, and recovery of the polymer by washing and drying. Dimethylsulphoxide was used as the solvent for PA6, and formic acid for PA66, and methylethylketone was used as the non-solvent for both polymers. The recycled polymers were evaluated by determination of molecular weight, crystallinity and grain size. Excellent recoveries were achieved, with no deterioration in the polymer properties. 33 refs. 

Reactions that are related to the solvent properties of dimethylsulphoxide... 

Most protic solvents have both protogenic and protophilic character, i.e. they can split off as well as bind protons. They are called, therefore, amphiprotic. These include water, alcohols, acids (especially carboxylic), ammonia, dimethylsulphoxide and acetonitrile. Solvents that are protogenic and have weak or practically negligible protophilic character include acid solvents, such as sulphuric acid, hydrogen fluoride, hydrogen cyanide, and formic acid. 

Alkaline hydrolysis in a solvent (dimethylformamide, dimethylsulphoxide or dimethyl-acetamide) containing sodium hydroxide has been investigated [164]- Fabric geometry [165] and the degree of heat setting of the polyester also influence the results. As the temperature of heat setting was increased, the accelerating effect of dodecylbenzyldimethylammonium chloride decreased [166]. Basic-dyeable polyester is particularly sensitive to alkaline hydrolysis [167]. In some cases, saponification has been used to produce special effects such as a leather-like finish [168]. 

An early study on C02 reduction in non-aqueous solvents was carried out by Haynes and Sawyer (1967) who employed chronopotentiometry, controlled potential coulometry and galvanostatic methods to study the reduction of C02 at Au and Hg in dimethylsulphoxide (DMSO). 

C). The polymer dissolves in solvents such as dimethyl formamide, dimethylsulphoxide, etc. It is difficult to work with it as on heating it turns yellow and red due to linking of nitrile groups ... 

The use of ISEs in non-aqueous media(for a survey see [125,128]) is limited to electrodes with solid or glassy membranes. Even here there are further limitations connected with membrane material dissolution as a result of complexation by the solvent and damage to the membrane matrix or to the cement between the membrane and the electrode body. Silver halide electrodes have been used in methanol, ethanol, n-propanol, /so-propanol and other aliphatic alcohols, dimethylformamide, acetic acid and mixtures with water [40, 81, 121, 128]. The slope of the ISE potential dependence on the logarithm of the activity decreases with decreasing dielectric constant of the medium. With the fluoride ISE, the theoretical slope was found in ethanol-water mixtures [95] and in dimethylsulphoxide [23], and with PbS ISE in alcohols, their mixtures with water, dioxan and dimethylsulphoxide [134]. The standard Gibbs energies for the transfer of ions from water into these media were also determined [27, 30] using ISEs in non-aqueous media. 

The influence of the solvent on the process is very important. Polymerization of methacrylic acid onto poly(2-vinylpyridine) template was studied hy carrying out the process in solvents with different polarity, such as dimethylsulphoxide, DMSO,... 

The toxicity of silatranes is considerably influenced by the nature of the solvent. Thus, the toxicity of silatrane solutions in dimethylsulphoxide is considerably higher than in water and tween. On skin application 1-arylsilatranes in DMSO solutions are fairly toxic as well, but not toxic in the solid state and in aqueous solutions. 

Meanwhile, Reutov et al.4 had reported that reaction (1) followed first-order kinetics, first-order in alkylmercuric bromide and zero-order in mercuric bromide, when anhydrous dimethylsulphoxide (DMSO) was used as the solvent. This report was confirmed by Ingold and co-workers3 and hence is the first authentic record of a reaction following mechanism SE1. Over a six-fold variation in the initial concentration of a-carbethoxybenzylmercuric bromide and a three-fold variation in that of mercuric bromide, only the first-order rate coefficient with respect to the alkylmercuric bromide remained constant3. The rate coefficients reported by the two sets of workers are given in Table 1, together with the reported Arrhenius equations. 

The effect of lithium perchlorate on the rate of reaction (44) (R = Me, X = Br) in solvent dimethylsulphoxide is unfortunately within experimental error, so that a calculation on the above lines would be meaningless. Since, however, mechanism SE2(open) is in force when dioxan(4) water(l), of e25 = 10.5, is the solvent, it would not be unreasonable if a similar mechanism applied also to reaction (44) (R = Me, X = Br) when dimethylsulphoxide, of 25 = 46.5, is the solvent. 

Although no coordination complexes of tetraalkyltins with nucleophiles (i.e. Lewis bases) have been reported, it is known that trialkyltin chlorides can form coordination complexes with various Lewis bases. Bolles and Drago38 have shown that trimethyltin chloride forms 1 1 complexes with bases such as acetone, acetonitrile, dimethylsulphoxide, and pyridine. All of these complexes are formed exothermally (in inert solvents such as CC14), with values of Af/299 ranging from —4.8 to —8.2 kcal.mole-1 for the reaction... 

IODINOLYSIS OF TETRAALKYLTINS BY IODINE IN SOLVENT DIMETHYLSULPHOXIDE (DMSO)... 

It would be expected39 that in the ionisation of a neutral substrate, the addition of inert salts should produce considerable rate accelerations. In the race-misation of ( —)-a-carbethoxybenzylmercuric bromide by mechanism SE1 in solvent dimethylsulphoxide, however, the addition of inert salts was found to result in either rate acceleration (e.g. with LiN03) or retardation (e.g. with LiC104)43. 

Except for the SE1 reactions of pyridiomethyl-metal compounds in aqueous solution, nearly all the SE1 reactions amenable to kinetic study have proceeded in dipolar aprotic solvents such as dimethylsulphoxide (DMSO), DMSO/dioxan, and probably also in acetonitrile. There is no obvious reason why such solvents should stabilise the produced carbanions to a much greater extent than hydroxylic solvents, and so the accelerating influence of these aprotic solvents on SE1 reactions is not easily accounted for. The substrates involved have, to date, been either alkylmercury or alkylgold compounds. It is possible, therefore, that the influence of solvents such as DMSO is to stabilise the counter cation produced in reactions such as... 

The one-phase liquid system is more frequently encountered since many organic reactions are carried out in solution. Direct fractional distillation may separate the product, if it is a liquid, from the solvent and other liquid reagents, or concentration or cooling may lead to direct crystallisation of the product if this is a solid. However, it is often more appropriate, whether the required product is a liquid or solid, to subject the solution to the acid/base extraction procedure outlined above and considered in detail on p. 162. This acid/base extraction procedure can be done directly if the product is in solution in a water-immiscible solvent. A knowledge of the acid-base nature of the product and of its water solubility is necessary to ensure that the appropriate fraction is retained for product recovery. In those cases where the reaction solvent is water miscible (e.g. methanol, ethanol, dimethylsulphoxide, etc.) it is necessary to remove all or most of the solvent by distillation and to dissolve the residue in an excess of a water-immiscible solvent before commencing the extraction procedure. The removal of solvent from fractions obtained by these extraction procedures is these days readily effected by the use of a rotary evaporator (p. 185) and this obviates the tedium of removal of large volumes of solvent by conventional distillation. 

It should be noted that self-ionisation is not an essential prerequisite for a satisfactory polar solvent. Liquids such as acetonitrile CH3CN or dimethylsulphoxide SO(CH3)2 appear not to ionise but they make very useful solvents for electrolytes as well as for polar molecular substances. As with H20, NH3, H2S04 etc., they owe their solvent powers to their polarity, leading to dipole-dipole interaction in the case of polar molecules as solutes and ion-dipole attraction in the case of electrolytes. There may in addition be considerable covalent bonding, via coordinate bond formation, in the case of cations. In solvents which do undergo appreciable self-ionisation, coordination often needs to be considered explicitly in discussing acid/base and other reactions and equilibria. 

DIB is stable in the air it can be stored at room temperature for long periods, provided it is light-protected. It dissolves in several ordinary solvents, most of which react with it at elevated temperature. A study in some solvents, using iodometric titration for monitoring the loss of oxidation power of DIB with time, showed that benzene is one of the most inert DIB remained unaltered in it at 25-50°C after 24 h. In contrast, in dimethylsulphoxide (DMSO) at 25°C 97% decomposed after 24 h. Acetone, methanol, methylene chloride, chloroform, acetic acid and acetonitrile are suitable solvents at room temperature even though they are reactive at elevated temperature [3]. Anyway, heating is rarely required in reactions with DIB and in such cases it is for short periods of time, so that the solvent reaction is unimportant. 

In Sect. 1.3, photoinitiation by means of donor—acceptor complexes was described. In some cases, these complexes may play an important role even without the contribution of light energy. In the presence of aliphatic amines and CCI4, methyl methacrylate is polymerized at temperatures 300 K. In polar solvents (7V,7V-dimethy formamide, dimethylsulphoxide, chloroform), interaction of aliphatic amines as donors with methyl methacrylate as acceptor produces complexes [91] which yield initiating radicals with CC14 [92]... 

Kabanov et al. have studied the radical polymerization of acrylic acid in aqueous solutions [61] (see Chap. 4, Sect. 1.4). A crystaline, syndiotactic polymer was formed at pH 10.2-10.8. The kinetics of the photosensitized polymerization of acrylic acid was studied by Galperina et. al. [62], They observed a strong solvent dependence for the rate constant of propagation. At 293 K, kp[mol-1 dm3 s-1] = 22 500 in water, 4 200 in formamide, and 500 in dimethylsulphoxide. 

An outstanding exception is the solvation of ions in dimethylsulphoxide (DMSO)-water mixtures. While in dimethylsulphoxide AG (Ag ) related to water is negative, in highly aqueous DMSO mixtures Ag is preferentially hydrated The change of preferential solvation of an ion with solvent composition has also been noticed for other ions This behavior can be attributed to the stabilization ... 

Cell (D) has been used several times to determine the solvent transference number A of the sparingly soluble salt Ag2S04 in the binary solvent mixtures acetonitrile-water l, dimethylsulphoxide-water and dimethylsulphoxide-methanol In Fig. 3 the solvent transference number of Ag2S04 is plotted versus Xdmso =... 

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