Dimethyl Sulphoxide Solution Research Articles

Addition of cyanide ions to aromatic aldehydes: a competition method for the determination of equilibrium constants of nucleophilic addition reactions

The equilibrium concentration of the cyanide Meisenheimer adduct of 1,3,5-trinitrobenzene, formed from potassium cyanide–18-crown-6 and trinitrobenzene, in DMSO solution, is reduced in the presence of an aromatic aldehyde, with an accompanying decrease in the absorbance of the solution due to the intensely coloured Meisenheimer adduct. Equilibrium constants have accordingly been determined for the formation of the cyanide Meisenheimer adduct of trinitrobenzene and for the formation of members of a series of substituted benzaldehyde cyanohydrin anions in dimethyl sulphoxide solution.

Amylose complexing capacities of cis- and trans-unsaturated monoglycerides in relation to their functionality in bread

The functionality of saturated monoglycerides as crumb softeners in bread is generally attributed to their ability to form insoluble inclusion complexes with amylose. At 60°C, pure cis- and trans-unsaturated monoglycerides were shown to be inferior to glycerol monopalmitate as amylose complexing agents. This appeared to be due mainly to an unfavourable physical state of these compounds since liposomal dispersions of the unsaturated monoglycerides were found to form inclusion complexes to the same extent as saturated monoglycerides. In dimethyl sulphoxide solutions of monoglycerides, the unsaturated compounds were 20–30% more effective as complexing agents than the saturated monoglycerides. In white pan bread, prepared according to the straight-dough procedure with monoglycerides (0·3%, w/w, flour basis), the unsaturated monoglycerides were bound to the gluten and starch fractions at the dough stage to a higher extent than was glycerol monopalmitate. The saturated monoglyceride gave the greatest increase in bread volume. The saturated and trans-unsaturated monoglycerides were more effective than the cis-unsaturated compound in retarding finning of white pan bread. Amylograph studies showed increased peak viscosities for wheat flour heated with water and monoglyceride (0·5%, w/w, flour basis). The increase in viscosity correlated well with the ability to form inclusion compounds with amylose.

Kinetics of the reaction of chloromethylated phenols with aniline and substituted anilines

The kinetics of the reaction of several chloromethylated phenols with substituted anilines, mainly p-nitroaniline, were studied for dimethyl sulphoxide solution by conductivity measurements. Substitution of the chlorine atoms proceeds in two steps. In a reversible step hydrogen chloride is eliminated by a suitable base to form a quinone methide. The aniline is added to this intermediate in the second step, forming the anilinomethylphenol as the product. The base in the first step may be the solvent, if weakly basic anilines (e.g.p-nitroaniline) are used, or the aniline, if the reaction is carried out with more basic anilines (e.g. aniline itself).

The metabolic and pharmacokinetic disposition of mebendazole in the rat.

The metabolism and pharmacokinetics of mebendazole was studied in rats using [2'-3H]-mebendazole (biologically stable; specific activity 383.9 (mCi/mMol) and [2-14C]-mebendazole (specific activity 2.57 mCi/mMol). Analyses were performed by high pressure liquid chromatography and liquid scintillation spectrometry. About 85% of an intravenous dose was eliminated with the bile and the remainder with the urine. The majority of the dose was recovered as conjugated metabolites. The major metabolite (methyl-5(6)-(alpha-hydroxybenzyl)-2-benzimidazole carbamate) accounted for about 77% of the total recovered and 99% of it was conjugated. Anaerobic metabolism studies conducted in vitro with intestinal microorganisms obtained from rats indicated that metabolism of mebendazole did not occur in the gut, but that the intestinal microflora was able to hydrolyse conjugated metabolites which were eliminated with the bile. Mebendazole was found to have a biphasic elimination profile after intravenous administration. Its terminal plasma elimination half-life was 3.2 hours and its re-distribution half-life was 0.4 hour. After oral administration, as a solution in aqueous dimethyl sulphoxide, a bioavailability of 53% was obtained.

Rheology and microstructure of solutions of the microbial polysaccharide from Pseudomonas elodea

Rheological studies of solutions and gels of the microbial polysaccharide from the organism Pseudomonas elodea have been combined with X-ray diffraction studies of fibres and pulsed electric-birefringence studies of dilute solutions, to investigate the conformation and interaction of the polymer molecules. Rheological data are suggestive of a locally rigid conformation for the biopolymer in solution. X-Ray diffraction studies suggest that the molecules adopt a three-fold helical structure. O-Acetyl substituents have been shown to inhibit the packing of these helices into crystalline domains. Studies of pulsed electric-birefringence suggest an extended, kinetically rigid structure in solution. Dissolving the polysaccharide in dimethyl sulphoxide inhibits the gelation and shear-thinning characteristics of aqueous solutions. Comparative studies of electric birefringence of solutions in water and dimethyl sulphoxide suggest that the differences in rheological properties may result from a change in molecular conformation.

Hydride transfer from cyclohexadienyl anions: the reaction between the hydride Meisenheimer adduct of 2,4-dinitroaniline and 1,3,5-trinitrobenzene

The hydride Meisenheimer adduct of 2,4-dinitroaniline transfers hydride to 1,3,5-trinitrobenzene to form its corresponding hydride Meisenheimer adduct. The reaction is practically irreversible. In dilute solution in dimethyl sulphoxide it exhibits second-order kinetics and the observation of several sharp isosbestic points shows that it occurs without formation of any detectable intermediate species.

Interaction of phthalocyaninatoiron(II) with molecular oxygen. Kinetics and mechanism of the reaction in dimethyl sulphoxide

The reaction of phthalocyaninatoiron(II), FePc, with dioxygen in dimethyl sulphoxide solution has been studied kinetically by measuring the visible spectral changes occurring under high concentration conditions (h.c.c.: [FePc] = 1 X 10 −4 mol dm −3 or higher) and low concentration conditions (l.c.c.: 1 X 10 −5 mol dm −3 or lower). At h.c.c. the observed spectral variations (a decrease in intensity of the band at 653 nm and a parallel increase of a band at 620 nm) develop with an autocatalytic-like pattern and can be reversed either by nitrogen bubbling or dilution. The insoluble μ-oxo species (FePc) 2O is the final reaction product. Under l.c.c. the spectral changes (a decrease in intensity of the spectrum at all wavelengths within the range 550–750 nm) are associated with an irreversible degradation of the complex. This spectral trend is also observed under h.c.c. when use is made of a free radical inhibitor (2,6-di(tert-butyl)-4-methylphenol). The whole experimental picture is satisfactorily explained by a mechanism in which an intermediate oxenic species FePcO can either react with FePc, to give reversibly the μ-oxo compound, or can oxidize the solvent (or a species derived from the solvent). In the h.c.c. reaction FePc behaves as an O-atom transfer catalyst.

X-Ray and electrochemical investigation on a series of cobalt(II) complexes with quinquedentate ligands and their reactivity towards dioxygen

Cobalt(II) complexes with various derivatives of the linear quinquedentate ligand bis(salicylideneimine-3-propyl)amine have been prepared and their electrochemical behaviour and reactivity with dioxygen have been studied in dimethyl sulphoxide solution by cyclic voltammetry. A linear correlation was found between the cobalt(II)–cobalt(III) half-wave potentials (E½) and the logarithms of the electrochemically determined equilibrium constants for the formation of the 1 : 1 dioxygen adducts. Steric and conformational effects are also discussed in the light of the structure of the oxygen active form of the bis(salicylideneimine-3-propyl)methylamine derivative which has been determined from three-dimensional X-ray diffractomer data. Crystals of the compound are monoclinic, space group P21/a, with a= 13.275(3), b= 16.476(4), c= 11.483(3)Å, β= 94.71(4)°, and Z= 4. The structure has been refined by least-squares techniques to R= 0.108 for 1 366 unique reflections with I > 3σ(I). The co-ordination geometry around the cobalt atom can be described in terms of a distorted trigonal bipyramid formed by the three nitrogen and the two oxygen atoms of the ligand molecule.

The detection of trace amounts of trans-Pt(NH 3) 2Cl 2 in the presence of cis-Pt(NH 3) 2Cl 2. A high performance liquid chromatographic application of kurnakow's test

Treatment of mixtures of cis and trans Pt(NH 3) 2Cl 2 with thiourea (thu) gave Pt(thu) 4Cl 2 and trans [Pt(NH 3) 2(thu) 2]Cl 2 which were separated and quantified by high-performance liquid chromatography using a strong cation exchange column. Several platinum-thiourea compounds have been studied by NMR ( 1H, 13C, 195Pt), an increase in the coalescence temperature of the NH 2 resonances being observed as a result of co-ordination. The NMR data has also been used to show the presence of interactions between the Pt(thu) 2+ 4 and PtCl 2− 6 ions of [Pt(thu) 4][PtCl 6] in dimethylsulphoxide solution.

An improved colorimetric procedure for determining apparent and total amylose in cereal and other starches

An improved method for the colorimetric determination of amylose as its blue polyiodide complex is described. Starch is dissolved in urea—dimethylsulphoxide and aliquots of the solution are used to determine apparent amylose (measured in the presence of any amylose complexing monoacyl lipids which may be present) and total amylose (measured on lipid-free starch, precipitated from urea—dimethylsulphoxide solution with ethanol). When factors such as ionic concentration, sequence and timing of steps in the procedure and solution temperature are controlled, the coefficient of variation in replicate determinations ( n = 6) is 0·2–10·0%, except with waxy starches, where it is 10·6–10·8%. The limitations of the method and sources of error in published methods for the preparation of lipid-free starches and in the development of stable amylose-polyiodide colour complexes are discussed. In some wheat and non-waxy rice starches the difference between total and apparent amylose is 30·5–7·4% amylose.

The binding of aluminium to [Leu 5]-enkephalin an investigation using 1H, 13C and 27Al NMR spectroscopy

The binding of aluminium ion to [Leu 5]-enkephalin has been investigated by 1H, 13C and 27Al NMR spectroscopy in dimethyl sulphoxide solution at different peptide/metal ratio. Analysis of the spectra suggests that Al 3+ binds at two metal-binding sites. The binding of Al 3+ at the first site involves the Tyr 1CO, and Leu 5COO − groups to give a 2:1 species in a tetracoordinated structure; whereas the binding of Al 3+ at the second site utilizes the NH 2 terminal groups of the tyrosine moiety in a 2:2 species. 27Al chemical shift values strongly suggests that the second type of aluminium atom displays an octahedral environment. On this basis, we discuss our data in terms of the coordination of aluminium with [Leu 5]-enkephalin.

Studies of the conformation of bilirubin and its dimethyl ester in dimethyl sulphoxide solutions by nuclear magnetic resonance.

The conformation of bilirubin and its dimethyl ester in dimethyl sulphoxide (DMSO) was investigated by n.m.r. spectroscopy. The chemical shifts of the pyrrole NH and Lactam protons of bilirubin and its dimethyl ester in DMSO indicate a strong interaction with the solvent. Inter-proton distances were calculated from nuclear Overhauser effects (NOE), selective and non-selective relaxation times (T1) and rotational correlation times taken from 13C relaxation times. The interproton distances indicate that the conformation of the skeleton of bilirubin and its dimethyl ester in DMSO is similar to that of bilirubin and mesobilirubin in the crystalline state and in chloroform solutions, except for a possible slight twist of the pyrrolenone rings about the methine bonds, which may be a consequence of solvation of the NH groups by DMSO. Unlike in chloroform solutions, no direct hydrogen-bonding occurs between the carboxylic acid and the lactam groups of bilirubin in DMSO, as shown by the absence of an NOE between these groups. The fast exchange of the pyrrole NH protons with 2H shows that no hydrogen-bonding occurs between these protons and the propionic residues, in line with their solvation by DMSO. From the above results, and from the slowness of the internal motion of the propionic residues of bilirubin and its dimethyl ester, it is concluded that these residues are tied to the skeleton via bound solvent molecules.

Assignment and analysis of the 500 MHz 1H NMR spectra of somatostatin and the acyclic precursor (S3,14‐Acm)‐somatostatin in dimethyl sulphoxide

AbstractThe 500 MHz 1H NMR spectra of somatostatin and the precursor, di‐S3,14‐acetamidomethyl dihydrosomatostatin, in dimethyl sulphoxide solution have been assigned. Chemical shifts, coupling constants and NH shifts vs temperature coefficients are tabulated. The data are consistent with a stable β‐turn/β‐sheet conformation for the precurso, while somatostatin itself appears to be more conformationally mobile, with an average conformation significantly different from that in aqueous solution.

Secondary structure in glycosaminoglycuronans: N.m.r. spectra in dimethyl sulphoxide of disaccharides related to hyaluronic acid and chondroitin sulphate

1H-N.m.r. spectra for solutions in dimethylsulphoxide- d 6 of disaccharides related to hyaluronate and chondroitin sulphate are compared with those of their methylated derivatives. All resonances, including those of HO and HN groups, have been assigned. The temperature and concentration dependences suggest that HO-4 of the hexosamine residue in hyalobiouronate (but not that in chondrosinate) is hydrogen-bonded to O-5 of the uronic acid residue. The resonance of HO-2 of the uronate residue of chondrosinate also shows anomalies that may arise from intra-residue hydrogen-bonding. These findings confirm the existence of some features previously suggested to be present in glycosaminoglycuronan polymers. The resonance of HO-4 of the uronate residue in the disaccharides and in sodium (methyl α- d-glucopyranosid)uronate behaves as though there was a hydrogen bond between the carboxylate group and HO-4.

Homopolysaccharides interaction with the dimethyl sulphoxide–paraformaldehyde cellulose solvent system. Selective oxidation of amylose and cellulose at secondary alcohol groups

A 13C n.m.r. study of the interaction properties of the cellulose solvent dimethyl sulphoxide–paraformaldehyde with amylose suggests the reversible formation of hemiacetals between formaldehyde or its oligomers and hydroxy-groups at C-6 and C-2 of the polysaccharide. Such selectivity is, however, not found for the model compound methyl 4-O-methyl-α-D-glucopyranoside, which shows O-3 substitution as well. In agreement with this result, oxidation of amylose in this solvent system by adding acetic anhydride to the homogeneous solution leads to selective formation of carbonyl groups at C-3 in excellent yield. A similar result is obtained when acetic anhydride is added to a cellulose solution in dimethyl sulphoxide–paraformaldehyde. This suggests that the interaction mechanisms of cellulose and amylose with this solvent system must be similar. As a matter of fact, oxidation of a 6-substituted cellulose, such as 6-O-acetylcellulose, mainly takes place at C-2. The 6-O-acetylcellulose was prepared by the action of acetic acid–acetic anhydride in pyridine–tetrachloromethane on a pertrimethylsilyl-cellulose followed by hydrolysis of the remaining 2,3-bis(trimethylsilyl) ether. Previous results on the oxidation of 6-O-triphenylmethyl-cellulose or -amylose have been confirmed and corroborated. Determination of the site and degree of oxidation with the partly oxidized homopolysaccharides was achieved through their reduction with sodium borodeuteride, hydrolysis, and study by g.l.c.–mass spectrometry of the resulting hexoses in the form of their trimethylsilyl O-methyl oximes, or alditol acetate derivatives.

Free radical polymerization of acrylonitrile in dimethylsulphoxide solutions

The gamma-ray initiated polymerization of acrylonitrile in DMSO solutions was investigated at various monomer concentrations and temperatures. In a narrow range of monomer concentrations (70–80%), the “auto-acceleration index” of the reaction is higher than in the bulk polymerization. Some auto-acceleration persists at high DMSO contents when the reaction proceeds in a homogeneous medium. The results are interpreted by a “matrix effect” which is enhanced in those mixtures in which the precipitated polymer particles are swollen to a larger extent by the reacting mixture.

Dicopper(II) complexes of a macrocyclic ligand containing single hydroxo-, methoxo-, or 1,1-azido-bridges: synthesis, magnetic properties, electron spin resonance spectra, and the crystal and molecular structure of a µ-hydroxo-derivative

Reaction of 2,6-diacetylpyridine with 1,3-diaminopropane in methanol in the presence of M[ClO4]2(M = SrII or BaII) in 2:1:1 molar proportions yields the complexes [ML2(ClO4)2] of the new 20-membered macrocyclic tetraimine ligand L2 derived from the [2 + 2] condensation of 2 mol of diketone with 2 mol of diamine. The single Ba2+ in [BaL2(ClO4)2] may be replaced by two Cu2+ to afford, depending on the conditions, the complexes Cu2L2(OH)(ClO4)3·2H2O and Cu2L2(OMe)(ClO4)3˙2H2O formulated as containing two Cu2+ linked by, respectively, single hydroxo- and methoxo-bridges. Crystals of the µ-hydroxo-complex are tetragonal with a= 15.20(1), c= 14.50(1)A, Z= 4, and space group P42/n. 1 191 Reflections above background were measured by diffractometer and refined by Fourier methods to R 0.078. Each copper atom in the binuclear [Cu2L2(OH)(OH2)]3+ cation is bonded to the three nitrogen atoms of a trimethine group of the folded macrocycle [Cu–N 1.916(13)–2.066(12)A]. The approximate co-ordination square plane about each metal atom is completed by a shared oxygen atom, O(1)(presumed to be from OH–), at 1.916(9)A. The two Cu atoms are also linked in a shared axial position by a second oxygen atom, O(2)(presumed to be from H2O), at 2.519(12)A. The Cu–O(1)–Cu and Cu–O(2)–Cu angles are 110.3(7) and 77.3(4)°, respectively, and the Cu ⋯ Cu separation is 3.145(4)A. Magnetic susceptibility measurements in the temperature range 90–300 K establish that the two Cu2+ in each binuclear complex are antiferromagnetically coupled with J=–32 and –53 cm–1 for the µ-hydroxy- and µ-methoxo-derivatives, respectively, where 2J is the singlet–triplet separation. The appearance of a ‘ triplet ’ e.s.r. spectrum at g≈ 2 and a seven-line ΔM= 2 half-band spectrum at g≈ 4 for frozen methanol–dimethyl sulphoxide solutions of the µ-methoxo-complex indicate retention of the bridge in solution. Reaction of Cu2L2(OMe)(ClO4)3·2H2O with Na[N3] affords Cu2L2(N3)(ClO4)3 for which i.r. spectra suggest that the Cu2+ are intramolecularly linked by one nitrogen atom of the azide ion (µ-1,1-N3 bridging mode). E.s.r. spectra of frozen solutions of the monoazide show that the Cu2+ are weakly antiferromagnetically coupled. The structures and physical properties of the complexes are discussed in relation to the cavity size of the macrocycle L2.

Secondary structures of hyaluronate and chondroitin sulphates. A 1H n.m.r. study of NH signals in dimethyl sulphoxide solution.

1H n.m.r. spectra in [2H6]dimethyl sulphoxide of dodecyltrimethylammonium salts of chondroitin sulphates and hyaluronate, or sodium salts of oligomers from hyaluronate, showed unambiguous NH signals. The acetamido NH occurs in two different environments: environment I ('normal') in simple sugars, and environment II (hydrogen-bonded NH) appearing in tri- or tetrasaccharides, indicating a secondary structure in hyaluronate (and some chondroitin sulphates) involving a hydrogen-bonded acetamido NH.

Carbon‐13 nuclear magnetic resonance study of the motional behaviour of bilirubin and of some of its derivatives

AbstractA comparative study of the spin‐lattice relaxation times (T1) of proton‐bearing carbons in bilirubin and its derivatives is reported. The NT1 values of the backbone carbons indicate that the overall reorientation of the molecule is isotropic. In dimethyl sulphoxide solutions, the segmental motion of the propionic side chains is very limited in bilirubin, bilirubin dimethyl ester and mesobilirubin dimethyl ester, faster in dimethoxybilirubin dimethyl ester and is very fast in the propionic residue of vinylneoxanthobilirubinic acid methyl ester. The relative mobilities of the propionic residues are interpreted on the basis of intramolecular hydrogen bonding in which the solvent participates. The dimeric form of bilirubin dimethyl ester in chloroform solutions is confirmed by the correlation time of tumbling of the backbone. In this solvent the segmental motion of the propionic side chains is rapid, indicating the probable absence of hydrogen‐bonding. In bilirubin, bilirubin dimethyl ester and dimethoxybilirubin dimethyl ester, internal rotation is rapid for the endo‐vinyl group and slow for the exo group, correlating with reported differences in the chemical behaviour of these residues in bile pigments.

Crystal structure and carbon-13 nuclear magnetic resonance spectrum of [NMe4]2[Fe4S4(SCH2CH2OH)4] and electron spin resonance spectrum of [Fe4S4(SCH2CH2OH)4]3? in aqueous solution

The compound [NMe4]2[Fe4S4(SCH2CH2OH)4] is triclinic, space group P, with a= 10.686(9), b= 11.288(8), c= 15.021(11)A, α= 99.0(1), β= 91.8(1), γ= 108.4(1)°, and Z= 2. 2 115 Independent reflections measured on a diffractometer have been refined to R= 0.088. The anion contains the Fe4S4 cubane-like cluster core distorted from Td symmetry such that four approximately parallel Fe–S bonds are shorter (mean 2.239 A) than the other eight (mean 2.306 A). There are two strong intermolecular O ⋯ H–O hydrogen bonds (O ⋯ O 2.63, 2.70 A) and there may be an intermolecular S ⋯ H–O hydrogen bond(S ⋯ O 3.16 A). Carbon-13 n.m.r. (90 MHz) spectra have been recorded for the title compound in dimethyl sulphoxide solution between 317 and 363 K; the resonance position of thiolate carbon was observed between 103.3 and 106.4 p.p.m. downfield of SiMe4. The anion [Fe4S4(SCH2CH2OH)4]3–, generated by dithionite treatment of the title compound in buffered aqueous solution containing excess of 2-hydroxyethanethiol and stabilised by rapid freezing, exhibits an axially symmetric e.s.r. spectrum with g∥= 2.045 and g⊥= 1.929 (= 1.967); similar treatment of the title compound with K3[Fe(CN)6] also generated a species having an axially symmetric e.s.r. spectrum, with g∥= 1.963 and g⊥= 2.006.