Dimethyl sulphoxide

DMF, Me2NC(0)H. Dimethyl formamide. DMSO, Mc2SO. Dimethyl sulphoxide. 

The laboratory preparation of the Udel-type polymer has been described. Bis-phenol A is mixed with chlorobenzene (solvent) and dimethyl sulphoxide (active solvent) and heated to 60°C to obtain a clear solution. Air is displaced from the system by nitrogen or argon and an aqueous solution of caustic soda added. This results in a two-phase system, one predominantly chlorobenzene the... 

The condensation reaction is promoted by certain polar solvents and of the many which have been tested dimethyl sulphoxide appears to be the most effective. As usual with linear condensation polymers molecular equivalence and near-absence of monofunctional material is necessary to ensure a high molecular weight. Moisture and alcohols can also have a devastating effect on the molecular weight. In the case of water it is believed that 4-chlorophenyl 4-hydroxyphenyl sulphone is formed which functions as an effective chain terminator. Gross contamination with air is also believed to reduce the maximum attainable molecular weight as well as causing intense discolouration. 

Sulphide and sulphoxide complexes have been extensively studied since cis-RuC12(DMSO)4 (DMSO, dimethyl sulphoxide, (Me)2SO) was found to have anti-tumour properties and to be a precessor for radiosensitizing agents. Such complexes can act as catalysts for the oxidation of sulphides with molecular oxygen. 

Shatenshtein et al.5 5 5- 591 have also measured rate coefficients for dedeuteration of thiophen derivatives by lithium or potassium l-butoxides in dimethyl sulphoxide or l-butyl alcohol (70 vol. %) in diglyme (Table 178). Interestingly, the 2 position is more reactive than the 3 position and this was reasonably attributed to the —I effect of the hetero sulphur atom. The methyl substituent lowers the reactivity of the 2 position from each position in accord with its +1 effect and consequently the effect was greatest from the 3 position. However, the deactivation from the 5 position was greater than from the 4 position, and this was incorrectly attributed to the +M effect of methyl group operating from the 5 position since... 

RATE COEFFICIENTS FOR REACTION OF [2H]-THIOPHENES WITH f-BuO— IN DIMETHYL-SULPHOXIDE OR f-BuOH (70 VOL. %) IN DICLYME 30 VOL. %)555 591... 

For the exchanges carried out in liquid ammonia, kinetic isotope effects kD kT of 2.3-2.5 have been obtained for reaction of benzene, toluene, and naphthalene and for the reactions of the 2 positions of furan and thiophene with -butoxide in dimethyl sulphoxide somewhat lower values, 1.5 and 1.3, respectively, were obtained591, but whether this was a solvent or a substituent effect is not apparent from the data. 

The effects of substituents have been determined in the cleavage of diaryl-mercury compounds by hydrogen chloride in dimethyl sulphoxide-dioxan at 32 °C. Rates were measured within the temperature range 12.8-75.0 °C, though over a range of not more than 18 °C for each compound611 (Table 184). The... 

TABLE 2. Analytical expressions for some symmetry coordinates" in dimethyl sulphoxide and dimethyl sulphone11... 

Dimethyl sulphide, dimethyl sulphoxide, dimethyl sulphone... 

Table 8 gives the complete population analysis for these molecules. Propane has been added for the same reason for which methane was considered above. Figure 14 gives the MOs of dimethyl sulphoxide, and Figure 15 the topmost ones of dimethyl sulphone. 

FIGURE 14. The MOs of dimethyl sulphoxide. Hydrogen atom contributions are not shown they can be inferred from the FOs of CH3, Figure 3b. 

In general, the publications cited here pertain to methods valid for several sulphoxides, even though some other compound classes may have been studied at the same time. However, many methods for dimethyl sulphoxide alone are also given on account of the considerable current importance of this compound. 

Aravamudan and Venkappayya75 oxidized dimethyl sulphoxide in acetate buffer of pH 4 to 4.5 and with a reaction time of only 1 min. They then added potassium iodide and acid and titrated with thiosulphate the iodine liberated by unused reagent. They reported that cerium(IV) and Cr(VI) were much less effective oxidizing reagents for the sulphoxide. A very similar procedure was used by Rangaswama and Mahadevappa76 to determine dimethyl sulphoxide and numerous other compounds with chloramine B. 

Bohme77 employed excess monoperphthalic acid in diethyl ether to oxidize dibenzyl and benzyl ethyl sulphoxides. Reaction time was 24 h at - 15 to + 10 °C, after which he added potassium iodide and water and titrated the iodine set free with thiosulphate. Dickenson78 oxidized dimethyl sulphoxide in malt, wort or beer with Na2S2Os. In... 

It is probable that the test of Wolski88 for sulphoxides depends on the first reaction. He used acetyl chloride or bromide the product from the former gave a red colour with nitrite ion, absorption maximum at 545 nm, and the latter gave a yellowish-orange colour directly. The method was used also by Besyadetskaya and colleagues89 to determine dimethyl sulphoxide in ointments. 

An example of determination of dimethyl sulphoxide (in solutions and ointments) was given by Kram and Turczan124. They recorded the NMR spectra at 60 MHz of the sulphoxide in methanol + water or chloroform and integrated the peaks the amount of sulphoxide was calculated from the ratio of its peak area to that of methanol. 

Popova and colleagues47 carried out TLC of oxidation products of 4,4 -dinitrodiphenyl sulphide (the sulphoxide and sulphone) on silica gel + a fluorescent indicator, using hexane-acetone-benzene-methanol(60 36 10 l) as solvent mixture. Morris130 performed GLC and TLC of dimethyl sulphoxide. For the latter, he applied a 6% solution of the sample in methanol to silica gel and developed with methanol-ammonia solution(200 3), visualizing with 2% aqueous Co11 thiocyanate-methanol(2 1). HPLC separations of chiral mixtures of sulphoxides have been carried out. Thus Pirkle and coworkers131-132 reported separations of alkyl 2,4-dinitrophenyl sulphoxides and some others on a silica-gel (Porosil)-bonded chiral fluoroalcoholic stationary phase, with the structure ... 

Corey and Chaykovsky were the first to investigate the reaction of dimethyl sulphoxide anion (dimsyl anion) with aldehydes and ketones400,401. They found that the reaction with non-enolizable carbonyl compounds results in the formation of /1-hydroxyalkyl sulphoxides in good yields (e.g. Ph2CO—86%, PhCHO—50%). However, with enolizable carbonyl compounds, particularly with cycloalkanones, poor yields of hydroxyalkyl products are observed (e.g. camphor—28%, cyclohexanone—17%, but... 

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