Water activity,osmotic and activity coefficients of aqueous solutions of Li2SO4, Na2SO4, K2SO4, (NH4)2SO4, MgSO4, MnSO4, NiSO4, CuSO4, and ZnSO4 at T=298.15 K

The water activities for aqueous solutions of Li₂SO₄(aq), Na₂SO₄(aq), K₂SO₄(aq), (NH₄)₂SO₄(aq), and sulphates MgSO₄(aq), MnSO₄(aq), NiSO₄(aq), CuSO₄(aq), and ZnSO₄(aq) were determined experimentally at a temperature of 298.15 K with a hygrometric method, at molalities in the range from 0.1 mol·kg⁻¹ to saturation. The osmotic coefficients are calculated from these results. The coefficients of Pitzer’s model was used to fit the osmotic coefficients for each salt solution. These parameters were used to predict solute activity coefficients for the salts studied.     

Novel solid-phase extraction method to separate 4-desmethyl-, 4-monomethyl-, and 4,4'-dimethylsterols in vegetable oils

Conventional methods for sterol fractions separation by TLC have some drawbacks such as low recovery and time consuming. A new solid-phase extraction (SPE) method was developed with stepwise elution by increasing the polarity of solvents mixture: n-hexane and diethyl ether. This method was applied to separate sterol fractions of hazelnut and virgin olive oils, and our results were compared with those of TLC method. The recovery of spiked authentic sample of 4-desmethylsterols in oil was higher with the SPE method (94%) compared with the TLC method (62%). The amount of 4,4'-dimethylsterols and 4-desmethylsterols separated with SPE in both hazelnut and virgin olive oil samples were at least 75% and 35%, respectively, higher than that of TLC. Generally, both methods obtained similar results for 4-monomethylsterols of the two oils. This new SPE method to separate phytosterol fractions was less time consuming, simpler and can be used instead of preparative TLC to detect adulteration of virgin olive oil with hazelnut oil.     

Simultaneous determination of paracetamol, chlorzoxazone, and related impurities 4-aminophenol, 4'-chloroacetanilide, and p-chlorophenol in pharmaceutical preparations by high-performance liquid chromatography

This paper presents a simple, specific, and precise high-performance liquid chromatographic method for the simultaneous determination of paracetamol (PCM), chlorzoxazone (CXZ), and their related impurities in bulk raw materials and solid dosage forms. The mobile phase consisted of water-methanol-glacial acetic acid (60 + 40 + 2, v/v/v). A column containing octadecylsilane chemically bonded to porous silica particles (Spherisorb ODS 1, 25 cm x 4.6 mm, 5 microm) was used as stationary phase. Detection was performed using a variable wavelength ultraviolet-visible detector set at 272 nm for all compounds. Solutions were injected into the chromatograph under isocratic condition at a constant flow rate of 1.2 mL/min. The method was validated according to International Conference on Harmonization requirements and demonstrates good accuracy and precision and a wide linearity range. The method separates PCM, CXZ, and 3 major impurities [4-aminophenol (4AP), 4'-chloracetanilide (4CA), and p-chlorophenol (PCP)] with fair resolution in less than 15 min. The developed method is rapid and sensitive (limit of detection for 4AP, 4CA, and PCP established at 31.25, 39.06, and 65.16 ng/mL, respectively) and, therefore, suitable for quality control and stability studies of these compounds in dosage forms.     

Crystal Structure of 3, 4-trans-4, 5-trans-2-Amino-3-cyano-1, 3-diethyloxy carbonyl- 4, 5-di (4-chlorophenyl)cyclopentene

1INTRoDUCT1oNThechemistriesofsamariumdiiodideandlow-valenttitaniumareofcurrentin--.terestinorganicSynthesis.Theyhavebeenwidelyusedinsyntheticreactions(l.2i.Thereactivityofthereagentstowardsvariousnitrogen-containingcomPOundshasal-readybeenexamined.Thereare,toourknowledge,noliteratureexamplesforthereductionofafylidenecyanoacetatederivativeswiththesereagents.Recently,wefoundthatthetitlecompoundisobtainedbycyclodimerizationreactionofpchlorObenzylidenecyanoacetatewithsamariumdiiodideorlow-va…     

Synthesis of acetylenic β-diketones and their conversion into 4H-pyran-4-ones,pyrazoles, and 1-hydroxy-4-pyridones

A simple method for the synthesis of acetylenic β-diketones is described. They can be cyclized to the corresponding 4H-pyran-4-ones with acids. Their reaction with hydrazine hydrate gave pyrazole derivatives isomeric with those obtained from 4H-pyran-4-ones. With hydroxyl-amine hydrochloride in ethanol, 1-hydroxy-4-pyridones are formed.     

Researches on 1, 2, 4-triazoles

A new method of preparing 1, 2, 4-triazolinethione derivatives by directly sulfurating the corresponding triazoles is described. 4-(-Pyridyl)-1, 2, 4-triazoline-3-thione undergoes aminomethylation, cyanoethylation, and pyridylethylation at the nitrogen of the thioamide group. Replacement of the phenyl group in 4-phenyl-1, 2, 4-triazolinethione by -pyridyl, gives a compound closely resembling 1-phenyltetrazoline-5-thione in its properties.For Part VII see [1].     

Theoretical study on tetranuclear boron clusters: B4X4 (X = H, F, Cl, Br, I)

The molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4 and B4I4 have been calculated by using all-electron or effective core potential ab initio method at the self-consistent field level using basis sets with diffuse and polarization functions. The boron-boron and boron-halide (-hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three-centered two-electron (3c2e) B-B-B bonds localized on each of the faces of the B4 tetrahedron are derived for B4X4 clusters. The HOMO-LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4 > B4Cl4, B4H4 > B4Br4 > B4I4.     

Single-step procedure for the extraction and purification of leukotrienes B4, C4 and D4

A rapid and simple method for the on-line concentration and high-performance liquid chromatographic (HPLC) purification of the leukotrienes in good yield from biological fluids is described. Readily available antisera are used in conjunction with this system to give a specific and sensitive assay for leukotrienes B4, C4 and D4 with sub-nanogram limits of detection. Tritium-labelled leukotrienes are used as internal standards, both to locate the leukotrienes post-HPLC and to accurately determine recoveries.     

Vibrational spectroscopic study of the mineral pitticite Fe, AsO4, SO4, H2O

Some minerals are colloidal and show no X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the determination of the structure of these minerals. Among this group of minerals is pitticite, simply described as (Fe, AsO(4), SO(4), H(2)O). In this work, the analogue of the mineral pitticite has been synthesised. The objective of this research is to determine the molecular structure of the mineral pitticite using vibrational spectroscopy. Raman and infrared bands are attributed to the AsO(4)(3-), SO(4)(2-) and water stretching and bending vibrations. The Raman spectrum of the pitticite analogue shows intense peaks at 845 and 837cm(-1) assigned to the AsO(4)(3-) stretching vibrations. Raman bands at 1096 and 1182cm(-1) are attributed to the SO(4)(2-) antisymmetric stretching bands. Raman spectroscopy offers a useful method for the analysis of such colloidal minerals.     

Reaction of 4H-1, 3-benzoxazine-4-onium salts with C-nucleophilic aromatic compounds

A method is proposed for the synthesis of 2-(4-dialkylaminophenyl)-2,3-dihydro-4H-1,3-benzoxazin-4-ones and diindolylcyaninemethanes by reaction of 4H-1,3-benzoxazin-4-onium salts with N,N-dialkylanilines and indole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 47–50, January, 1977.     

2, 5-Dialkyl-1, 3, 4-oxadiazoles

A single stage method has been developed for the preparation of 2, 5-dialky-1, 3, 4-oxadiazoles from aliphatic carboxylic acids, by boiling with hydrazine hydrochloride in phosphoryl chloride. A mechanism for the synthesis is suggested. The oxadiazoles are characterized, and the group refractivity of the 1, 3, 4-oxadiazole ring has been determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1171–1175, September, 1970.     

Synthesis,Crystal Structures,and Optical Properties of New Quaternary Metal Chalcogenides of Group 5: Cs2AgVS4, K2AgVSe4, Rb2AgVSe4, Rb2AgNbS4, and Cs2AgNbSe4

The new quaternary compounds Cs₂AgVS₄, K₂AgVSe₄, Rb₂AgVSe₄, Rb₂AgNbS₄, and Cs₂AgNbSe₄ were prepared using the reactive flux method. In this structure type infinite chains of edge-sharing AgQ₄- and M^VQ₄-tetrahedra are running parallel to the crystallographic a-axis. The chains are separated by alkali cations. A linear relationship between the size of the alkali cation A⁺ and the Q–Q interchain distances was found. These compounds are isostructural with the analogous quaternary copper chalcogenides. The optical properties were studied by collecting UV/Vis transmission and reflectance spectra which allowed to derive the optical band gaps. The colours of the vanadium compounds range from black to dark violet with optical band gaps between 1.7 and 1.8 eV. In addition, the behaviour of the samples was studied using polarized light. Under these experimental conditions the niobium compound Rb₂AgNbS₄ changes its colour from green to red when the direction of the polarization plane is changed by 90°.     

4-Thiazolidines,derivatives and analogs

Heating thiazan-2, 4-dione (I) with P₂S₅ in xylene or toluene gives a hitherto unknown isomer of propiorhodanine (II), 4-thione-1, 3-thiazan-2-one (III), with an active thione group and more acidic properties than II. Reaction of I with P₂S₅ in dioxane gave 2, 4-dithionethiazane, (IV) in high yield, this being the most convenient method of preparing IV.     

Conversion of 2,5-dialkyl-1,3,4-oxadiazoles into 4-substituted 3,5-dialkyl-1,2, 4-triazoles

2, 5-Dialkyl-1, 3, 4-oxadiazoles react on heating with primary amines to form 4-substituted 3, 5-dialkyl-1, 2, 4-triazoles, which is a convenient method for synthesizing these almost unknown compounds.     

B4C2,B2C4簇的从头算研究

用量子化学从头计算方法研究了Ｂ４Ｃ２，Ｂ２Ｃ４簇各种可能的几何构型，计算了相应的振动光谱。Ｂ４Ｃ２的稳定构型除直线，平面构型外还有三维模型，而Ｂ２Ｃ４的稳定构型均为直线、平面构型，因此，Ｂ４Ｃ２与Ｂ６接近，Ｂ２Ｃ４与Ｃ６接近。Ｂ－Ｃ和Ｃ－Ｃ多重键及强共轭效应是Ｂ４Ｃ２和Ｂ２Ｃ４簇稳定的重要因素。     

Synthesis of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts

A method for the preparation of 4-ethoxycarbonylmethyl-, 4-N-phenylcarbamoylmethyl-, and 4-carboxymethyl-1,3-dithiole-2-thiones and the corresponding 1,3-dithiolium salts from -bromoacetoacetic ester, -bromoacetoacetanilide, and sodium tertbutyltrithiocarbonate was developed. The compounds were characterized by their IR and PMR spectra.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 180–183, February, 1984.     

Relativistic all-electron molecular Hartree-Fock-Dirac-(Breit) calculations on CH4, SiH4, GeH4, SnH4, PbH4

Summary Results and details of molecular Fock-Dirac-(Breit) calculations on CH₄, SiH₄, GeH₄, SnH₄, and PbH₄ obtained with the MOLFDIR© program package are presented and compared with other calculations and experimental results. The relativistic ground state energies (including the Breit interaction) of the atoms C, Si, Ge, Sn, and Pb, necessary for reference purposes, have been calculated using a small relativistic CI. One of our findings is that for the heavier systems perturbation theory over-estimates the relativistic bond length contraction. The Breit interaction has only a small effect on the bond lengths.     

Spectrophotometric determination of lithium ion with the chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromethylphenyl-4′-aminobenzo-14-crown-4

A spectrophotometric method of determining alkali metal ions with a chromogenice crown ether reagent was found to be more selective and sensitive than an ion-pairing method based on the same size of crown ether cavity. It is shown that in the ion-pairing method, the sensitivity toward lithium ion was 5.685 × 10^?4 absorbance/mg l^?1, with sodium interfering at 300 mg l^?1. The chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromeethylphenyl-4′-aminobenzo-14-crown-4, was much superior to benzo-14-crown-4. The sensitivity of the chromogenic crown ether was 1.69 × 10^?3 absorbance/mg l^?1. This represents a three-fold increase in sensitivity and less reagent is needed (2 × 10^?4 M for the chromogenic method versus 1.4 × 10^?3 M for ion-pairing). Interference from sodium decreased to 3000 mg l^?1. The reagent was used to determine lithium ion in treated blood serum samples in both a batch and flow injection method and results were compared with data obtained with atomic absorption; excellent agreement was obtained in all cases.     

The crystal structure of LaIr4B4, ThOs4B4, ThIr4B4 (NdCo4B4-type) and URu4B4, UOs4B4 (LuRu4B4-type)

The crystal structure of LaIr₄B₄ has been refined from single crystal counter data. LaIr₄B₄ is tetragonal,P4₂/n,Z=2, isotypic with NdCo₄B₄, |F|/|F _o|=0.039 for 312 independent reflections [|F _o|>2 (F _o)]. ThIr₄B₄ and ThOs₄B₄ also belong to the NdCo₄B₄-type structure. URu₄B₄ and UOs₄B₄ were found to crystallize with LuRu₄B₄-type structure. The crystal chemistry of (RE)T ₄B₄-phases is discussed and simple geometric relations are shown to exist between them.Dedicated to Prof.B. T. Matthias in celebration of his 60th birthday.     

High-level ab initio predictions for the ionization energies and heats of formation of five-membered-ring molecules: thiophene, furan, pyrrole, 1,3-cyclopentadiene, and borole, C4H4X/C4H4X+ (X = S, O, NH, CH2, and BH)

The ionization energies (IEs) and heats of formation (ΔH°(f0)/ΔH°(f298)) for thiophene (C(4)H(4)S), furan (C(4)H(4)O), pyrrole (C(4)H(4)NH), 1,3-cyclopentadiene (C(4)H(4)CH(2)), and borole (C(4)H(4)BH) have been calculated by the wave function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled-cluster level with single and double excitations plus a quasi-perturbative triple excitation [CCSD(T)]. Where appropriate, the zero-point vibrational energy correction (ZPVE), the core-valence electronic correction (CV), and the scalar relativistic effect (SR) are included in these calculations. The respective CCSD(T)/CBS predictions for C(4)H(4)S, C(4)H(4)O, C(4)H(4)NH, and C(4)H(4)CH(2), being 8.888, 8.897, 8.222, and 8.582 eV, are in excellent agreement with the experimental values obtained from previous photoelectron and photoion measurements. The ΔH°(f0)/ΔH°(f298) values for the aforementioned molecules and their corresponding cations have also been predicted by the CCSD(T)/CBS method, and the results are compared with the available experimental data. The comparisons between the CCSD(T)/CBS predictions and the experimental values for C(4)H(4)S, C(4)H(4)O, C(4)H(4)NH, and C(4)H(4)CH(2) suggest that the CCSD(T)/CBS procedure is capable of predicting reliable IE values for five-membered-ring molecules with an uncertainty of ±13 meV. In view of the excellent agreements between the CCSD(T)/CBS predictions and the experimental values for C(4)H(4)S, C(4)H(4)O, C(4)H(4)NH, and C(4)H(4)CH(2), the similar CCSD(T)/CBS IE and ΔH°(f0)/ΔH°(f298) predictions for C(4)H(4)BH, whose thermochemical data are not readily available due to its reactive nature, should constitute a reliable data set. The CCSD(T)/CBS IE(C(4)H(4)BH) value is 8.868 eV, and ΔH°(f0)/ΔH°(f298) values for C(4)H(4)BH and C(4)H(4)BH(+) are 269.5/258.6 and 1125.1/1114.6 kJ/mol, respectively. The highest occupied molecular orbitals (HOMO) of C(4)H(4)S, C(4)H(4)O, C(4)H(4)NH, C(4)H(4)CH(2), and C(4)H(4)BH have also been studied by the natural bond orbital (NBO) method, and the extent of π-electron delocalization in these five-membered rings are discussed in correlation with their molecular structures and orbitals.