Acid In Dimethyl Sulphoxide Research Articles

Imine-tautomers of aminothiazole derivatives: intriguing aspects of chemical reactivities

Intriguing reactivities of positional isomers 1-(5-methylthiazol-2-yl)-3-(4-nitrophenyl)thiourea (L1) and 1-(4-methylthiazol-2-yl)-3-(4-nitrophenyl)thiourea (L2) towards environment polluting ions such as mercuric, fluoride, bromide and solvents provide scope to study various self-assemblies formed under different conditions and allied applications. The solid state structures of L1 and L2 revealed that both adopt the imine form. However, the number of symmetry independent molecules in asymmetric units as well as the packing patterns of these two compounds have distinguishable features. The asymmetric unit of L1 has three symmetry non-equivalent molecules. The packing patterns of these two positional isomers differ as L1 has two arrays of dimeric self-assemblies in contrast to the single array found in the packing of L2. The reactivity of L1 and L2 with solvents was explored through crystal structure elucidation. The compound L1 forms solvates with N,N′-dimethylacetamide or dimethylsulphoxide. The structural analysis of solvates of L1 provided avenues to study conformational adjustments. An unusual example of a metastable solvate of L1 with N,N′-dimethylacetamide was isolated. A ring-opening reaction of 1,8-diazabicyclo [5.4.0] undec-7-ene with L1 has been observed. The compound L2 underwent hydrolysis cum bromination with hydrobromic acid in dimethylsulphoxide. The reactivities of L1 and L2 towards mercuric and fluoride ions contributed to chemodosimetric signal transductions. The study establishes the impact of subtle changes in structure, reaction and crystallization conditions, which can influence pre-designed crystal engineering.

Synthesis of hydrophobic whey protein isolate by acylation with fatty acids

Due to its high availability, whey protein isolate (WPI) is an attractive feedstock for the production of bio-based materials. In the current study, different methods of synthesis are compared for the acylation of WPI with fatty acids. The aim is to synthesise hydrophobic, bio-based WPI derivatives for thermoplastic processing. Contrary to the acid chloride/pyridine acylation procedure, homogeneous acylation with carbonyldiimidazole (CDI)-activated fatty acids in dimethylsulphoxide (DMSO) enabled organic solvent soluble WPI derivatives to be synthesized. The substitution pattern and the degree of substitution (DS) were estimated by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and 1H NMR spectroscopy. The ATR-FTIR analyses showed qualitative differences in the degree of acylation of WPI achieved by the different synthesis methods. Solutions of WPI-laurate and -oleate in THF and CHCl3 were studied via dynamic light scattering (DLS), showing the influence of the type of esterified fatty acid on the particle size distribution. Water uptake experiments demonstrated the hydrophobicity of WPI-oleate. The thermal behaviour was studied by Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA). Thermoplastic behaviour of WPI-oleate was detected at 150°C, with 30% oleic acid (OA) as the plasticiser. Extrusion processing was tested using a WPI-oleate/OA mixture and using starch laurate as a blend component. In summary, a new type of WPI derivative has been synthesized and shows potential for thermoplastic processing.

Densities and Refractive Indices for N-Arylhydroxamic Acids in Dimethylsulphoxide at Various Temperatures

Densities and Refractive Indices for N-Arylhydroxamic Acids in Dimethylsulphoxide at Various Temperatures

Mesomorphic Behaviour of Lauric Acid in Dimethyl Sulphoxide

XRD, DSC and optical texture studies show that mixtures of lauric acid in dimethyl sulphoxide exhibit a lamellar mesophase.

Determination of vitamin B 12 in multivitamin-multimineral tablets by high-performance liquid chromatography after solid-phase extraction

A method for the determination of vitamin B 12 (cyanocobalamin) in multivitamin-multimineral tablets, containing 3 μg of vitamin B 12 per tablet, is described. Powdered tablets are extracted with a mixture of ammonium pyrrolidinedithiocarbamate and citric acid in dimethyl sulphoxide and water. The extract is centrifuged and the supernatant is diluted with water before concentration and clean-up by solid-phase extraction using a quaternary amine and a phenyl column in series. THe eluate from the solid-phase extraction is analysed by reversed-phase liquid chromatography using a methanol-water gradient with detection at 550 nm. A comparison with the frequently used microbiological method is presented. The validation of the procedure is described in terms of selectivity, linearity, accuracy and precision.

ChemInform Abstract: A Convenient Synthesis of 2‐Styrylchromones by Modified Baker‐Venkataraman Transformation Using Phase‐Transfer Catalysis.

Abstract Condensation of 2-hydroxyacetophenones 1 with cinnamic anhydrides 2 in the presence of tetra-n-butyl ammonium hydrogen sulphate in benzene-aqueous potassium carbonate biphase medium give 1-(2-hydrcxyphenyl)-5-phenyl-4-pentene-l, 3-diones 3 which on cyclodehydration using p-toluene sulphonic acid in dimethylsulphoxide give 2-styrylchromones 4 in high yields.

A Convenient Synthesis of 2-Styrylchromones by Modified Baker-Venkataraman Transformation Using Phase Transfer Catalysis

Abstract Condensation of 2-hydroxyacetophenones 1 with cinnamic anhydrides 2 in the presence of tetra-n-butyl ammonium hydrogen sulphate in benzene-aqueous potassium carbonate biphase medium give 1-(2-hydrcxyphenyl)-5-phenyl-4-pentene-l, 3-diones 3 which on cyclodehydration using p-toluene sulphonic acid in dimethylsulphoxide give 2-styrylchromones 4 in high yields.

ChemInform Abstract: The Decomposition of Trihalogenoacetic Acids in Dimethyl Sulphoxide: a Mild Route from Carbonyl Compounds to Trihalogenomethylethanol and Trihalogenomethyl Ketones.

Solutions of trichloro- and tribromo-acetic acid in dimethyl sulphoxide in the presence of carbonyl compounds react at room temperature to give insoluble products corresponding to addition of H–CX3 across the carbonyl double bond.

The decomposition of trihalogenoacetic acids in dimethyl sulphoxide: a mild route from carbonyl compounds to trihalogenomethylethanol and trihalogenomethyl ketones

Solutions of trichloro- and tribromo-acetic acid in dimethyl sulphoxide in the presence of carbonyl compounds react at room temperature to give insoluble products corresponding to addition of H–CX3 across the carbonyl double bond.

Trichloroacetic acid in dimethyl sulphoxide as a source of trichloromethyl anions: formation of an adduct and substitution product with 1,3,5-trinitrobenzene

Solutions of trichloroacetic acid in dimethyl sulphoxide generate trichloromethyl anions which can be trapped by species susceptible to nucleophilic attack, such as 1,3,5-trinitrobenzene; the procedure is preparatively useful.

Solution chemistry of NN′-ethylenebis(salicylideneiminato)iron(III). Part 1. Deprotonation equilibria and reversible decomposition in acid medium of NN′- ethylenebis(salicylideneimine). Stability constant of NN′- ethylenebis(salicylideneiminato)iron(III)

NN′-Ethylenebis(salicylideneimine), H2 salen, behaves as a weak diprotic acid in dimethyl sulphoxide (dmso)–H2O (80 : 20 w/w) solution. The values of the overall association constants are βj1=(1.63 ± 0.05)× 1012 dm3 mol–1 and βj2=(2.04 ± 0.02)× 1023 dm6 mol–2. H2 salen undergoes slow hydrolytic decomposition in acid medium [equations (i) and (ii)](Hsal = salicylaldehyde, en = ethylenediamine); βh1=(2.60 ± 0.05)× 104 and βh2=(1.60 ± 0.02)× 107. H2 salen + H+ [graphic omitted] Hsal + HOC6H4CHN(CH2)2NH3+(i), H2 salen + 2 H+ [graphic omitted] 2 Hsal + H2en2+(ii) The favourable thermodynamics for the hydrolysis are provided by the protonation of en. In neutral or basic media the hydrolysis is not spontaneous in spite of the large water content of the solvent. Solutions of [{Fe(salen)Cl}2] in dmso–H2O contain the cation [Fe(salen)]+. The chloride is completely displaced from the co-ordination sphere of FeIII by a solvent molecule, and [Fe(salen)]+ decomposes, in acid medium, very slowly [equation (iii)]. [Fe(salen)]++ 4 H+⇄ Fe3++ 2 Hsal + H2en2+(iii) The study of this equilibrium allows the stability constant of the complex, Fe3++ salen2–⇄[Fe(salen)]+, β=(7.1 ± 0.1)× 1025 dm3 mol–1 to be obtained. This is the first reported stability constant of a metal complex of H2 salen. All equilibrium constants were determined at 25 °C and 0.1 mol dm–3 KClO4 in dmso–H2O (80 : 20 w/w).

Characterisation by 1H- and 13C-n.m.r. spectroscopy of the products from oxidation of methyl α- and β- d-galactopyranoside with periodic acid in dimethyl sulphoxide

Oxidation of methyl α- and β- d-galactopyranoside with periodic acid in dimethyl sulphoxide gave, in each case, one major, monomeric product, isolated as a diacetate. These syrupy products were characterised by m.s. and 1H- and 13C-n.m.r. spectroscopy as (1 S,2 S,4 R,7 S)-7-acetoxy-4-acetoxymethyl-2-methoxy-3,6,8-trioxabicyclo[3.2.1.]octane and (1 S,2 R,4 R,7 S)-7-acetoxy-4-acetoxymethyl-2-methoxy-3,6,8-trioxabicyclo[3.2.1.]octane, respectively. Chemical shifts and coupling constants for the products were determined partly from the experimental n.m.r. spectra, and partly by an iterative fitting-procedure with the computer program NEMEN.

Conductance of acids in dimethylsulphoxide—I: Conductance of hydrochloric acid in DMSO—water mixtures at 25°C

Conductance measurements at 25°C are reported for dilute solutions of hydrochloric acid in dimethylsulphoxide and in dimethylsulphoxide—water mixtures containing up to 15% by weight of water. The results are analysed in terms of full Fuoss—Hsia conductance equation. Association constants decrease as the water content is increased whereas Λ α values pass through a minimum at about 11% water.

Equilibrium and kinetic acidities of carbon acids

Bnomalous Bronsted coefficients observed for nitroalkanes are rationalized in terms of a mechanism involving an intermediate anion. The results of measurements of equilibrium acidities of carbon acids in dimethyl sulphoxide (DMSO) solution are presented and compared with similar measurements made in solvents of low dielectric constant and in water. A linear correlation between gas-phase acidities and DMSO solution acidities for a series of ketones and for a series of nitriles is presented. Equilibrium measurements indicate the presence of a high degree of strain in the anion derived from trifluoromethylsulphonylcyclopropane. This result shows that the sulphur atom in the trifluoromethylsulphonyl group is entering into strong conjugation with the carbanion.

Photochemistry of ferrocenyl ketones and acids in dimethyl sulphoxide and related solvents

Compounds of the type FcCOAr, FcCOR (R = Alkyl), and FcCHO undergo photoaquation (λ > 280 nm) in wet dimethyl sulphoxide, pyridine, dimethylformamide, and related solvents to give a cyclopentadienyliron salt of the acid ArCO2H or RCO2H together with a molecule of free cyclopentadiene derived from the originally substituted ring. At shorter wavelengths in DMSO a secondary reaction gives rise to the intense purple colouration described previously. Ferrocenecarboxylic acid undergoes similar consecutive changes in these solvents yielding initially a carboxylate and free cyclopentadiene, but then CO2 and a new carboxylate from which starting material could be recovered in 48% yield. With shorter wavelength light a purple colouration developed. The esters of this acid were also found to be photosensitive but subject to strong autoretardation.

Acidity function in dipolar aprotic media

The H0 acidity function has been determined for hydrochloric and trichloroacetic acids in dimethyl sulphoxide (DMSO) and acetonitrile using three amine class of indicators. The variation of H0 with solvent composition at a fixed concentration of 0.1 M HCI in DMSO-water, acetonitrile-water and DMSO acetonitrile mixtures was also studied. Approximate medium effects on the proton in all these solvents were computed from the H0 data and the results are discussed.

The determination of sulphate in sea water by means of photometric titration with hydrochloric acid in dimethyl sulphoxide

The sulphate concentration in sea water has been determined by photometric titration to hydrogen sulphate in dimethyl sulphoxide solution with hydrochloric acid, using bromocresol green as indicator. The end-point is evaluated graphically and a complete titration can be performed in less than 15 min. Since borate, carbonate and hydrogen carbonate interfere, a separate determination of the alkalinity is necessary. The method can be used satisfactorily for sea water samples with a chlorinity of at least 2‰.

Ionization of some weak acids in dimethyl sulphoxide+water mixtures

The ionization constants of acetic, chloroacetic, dichloroacetic and trichloroacetic acids have been determined as functions of the solvent composition in dimethyl sulphoxide (DMSO)+water mixtures. A plot of pK against mol fraction DMSO is nearly linear, but plots of pK against the reciprocal of the dielectric constant, weight % DMSO, or the Z value of the solvent show marked curvature.

Acidity functions of some organophosphorus acids in dimethylsulphoxide and ethylene glycol

An acidity function scale ( DMSO H 0) has been set up in dimethyl sulphoxide solvent using primary aniline indicators. H 0 and DMSO H 0 values of several organophosphorus acids of the general formula (X)(Y)PO 2H (where X and/or Y may be phenoxyl, hydrogen, cyclo-hexoxyl, hydroxyl, phenyl or cyclohexyl) have been determined in ethylene glycol and dimethyl sulphoxide respectively. A linear free energy relationship between the DMSO H 0 value of a 0·200 M (X)(Y)PO 2H in dimethyl sulphoxide solution and the X and Y substituents is described by the equation DMSO H O= DMSO H O(H)(H)P o −∑d where d is the substituent constant and is defined as zero for H; and DMSO H 0(H)(H)P 0 is the theoretical DMSO H 0 value for the dihydrogen substituted acid, H 2PO 2H, and is found to have a value of 2·73 from a least squares plot.

Infra-red spectra of solutions of some acid salts of carboxylic acids in dimethylsulphoxide

Infra-red spectra of potassium hydrogen bisphenylacetate, di- p-chlorobenzoate, maleate, phthalate and di- p-nitrobenzoate dissolved in dimethylsulphoxide have been investigated and compared to the spectra of the respective crystals. Changes of the type of hydrogen bonding are discussed.