Pressure and temperature effects on the excess deuteron and proton conductance

The limiting molar conductances ° of deuterium chloride DCl in D₂O were determined as a function of pressure and temperature in order to examine the proton-jump mechanism in detail. The excess deuteron conductances °_E(D ⁺), as estimated by the equation [°_E(D ⁺) = °(DCl/D ₂ O) – °(KCl/D ₂ O)], increases with an increase in the pressure and temperature as well as the excess proton conductance [°_E(H ⁺) = °(HCl/H ₂ O) – °(KCl/H ₂ O)]. The isotope effect on the excess conductances, however, depends on the pressure and temperature contrary to the model proposed by Conway et al.: °_E(H ⁺)/°_E(D ⁺) decreases with increasing pressure and temperature. The magnitude of the decrease with pressure becomes more prominent at lower temperature. These results are discussed in terms of the pre-rotation of adjacent water molecules, the bending of hydrogen bonds with pressure, and the difference in strength of hydrogen bonds between D₂O and H₂O.     

Complex formation followed by internal electron transfer: The reaction between cysteine and iron(III)

Summary A kinetic study of the anaerobic oxidation of cysteine (H₂ L) by iron(III) has been performed over thepH-range 2.5 to 12 by use of a stopped-flow high speed spectrophotometric method. Reaction is always preceded by complex formation. Three such reactive complex species have been characterized spectrophotometrically: FeL ⁺ (_max=614 nm, =2 820 M^–1cm^–1); Fe(OH)L (_max=503 nm; shoulder at 575 nm, =1 640 M^–1cm^–1); Fe(OH)L ₂ ^2– (_max=545 nm; shoulder at 445 nm, =3 175 M^–1 cm^–1). Formation constants have been evaluated from the kinetic data: Fe³⁺+L ^2– FeL ⁺: logK ₁ ^M =13.70±0.05; Fe(OH)²⁺+L ^2– Fe(OH)L: logK ₁ ^MOH =10.75±0.02; Fe(OH)L+L ^2– Fe(OH)L ₂ ^2– ; logK ₂ ^MOH =4.76±0.02. Furthermore the hydrolysis constant for iron(III) was also obtained: Fe(OH)²⁺+H⁺ Fe _aq ³⁺ : logK ^FeOH=2.82±0.02). Formation of the mono-cysteine complexes, FeL ⁺ and Fe(OH)L, is via initial reaction of Fe(OH)²⁺ with H₂ L (k=1.14·10⁴M^–1s^–1), the final product depending on thepH. FeL ⁺ (blue) formed at lowpH decomposes following protonation with a second-order rate constant of 1.08·10⁵M^–1s^–1. Fe(OH)L (purple) decomposes with an apparent third order rate constant ofk=3.52·10⁹M^–2s^–1 via 2 Fe(OH)L+H⁺ products, which implies that the actual (bimolecular) reaction involves initial dimer formation. Finally, Fe(OH)L ₂ ^2– (purple) is remarkably stable and requires the presence of Fe(OH)L for electron transfer. A rate constant of 8.36·10³M^–1s^–1 for the reaction between Fe(OH)L and Fe(OH)L ₂ ^2– is evaluated.Dedicated to Prof. Dr. mult. Viktor Gutmann on the occasion of his 70th birthday     

Determination of Vitamins E and D3 in Some Preparations by High-Performance Liquid Chromatography with Indirect Spectrophotometric Detection

The behavior of vitamins E and D₃ was studied under the conditions of reversed-phase high-performance liquid chromatography with the use of unmodified and modified mobile phases. Acetonitrile modified with chlorophyll (a + b) (Chl) and tetraphenylporfyrin (H₂TPP) was selected for the indirect spectrophotometric detection of vitamins. It was demonstrated that detection limits are 2.3 g (8.33 × 10^–6 M H₂TPP, = 404 nm) and 3.5 ng (8.6 × 10^–6 M Chl, = 430 nm) for vitamin E and 0.12 g (3.0 × 10^–7 M H₂TPP, = 420 nm) for vitamin D₃. Pharmaceutical preparations containing vitamins E and D₃ were analyzed.     

Flavonoids of inflorescences of Calendula officinalis

By column chromatography on polyamide sorbent, the inflorescences of pot marigold calendula have yielded eight substances of flavonoid nature: two aglycons — quercetin (C₁₅H₁₀O₇, mp 309–311°C) and isorhamnetin (C₁₆H₁₂O₇, mp 314–316°C); six glycosides, of which three have been identified as isoquercetin (C₂₁H₂₀O₁₂, [] _D ²⁰ –36° in methanol, mp 218–220°C), isorhamnetin 3-O--D-glucoside (C₂₂H₂₂O₁₂, [] _D ²⁰ –59° in dimethylformamide, mp 193–195°C), narcissin (C₂₈H₃₂O₁₆, [] _D ²¹ –28° in dimethylformamide, mp 180–182°C), and three substances that have proved to be new and have been called calendoflaside (C₂₈H₃₂O₁₅, [] _D ²¹ –85° in methanol, mp 192–195°C; calendoflavoside (C₂₈H₃₂O₁₆, [] _D ²⁰ –106° in methanol, mp 189–192°C), and calendoflavobioside (c₂₇H₃₀O₁₆, [] _D ²⁰ –105° in methanol, mp 194–197°C).All-Union Scientific-Research Institute of Drug Chemistry, Khar'kov. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 795–801, November–December, 1988.     

An ESR and Optical Spectroscopic Study of the Mechanism of Photostimulated Reactions in Hydrogen Cyanide γ-Irradiated at 77 K

Changes in the electronic absorption spectra and ESR spectra in the course of photobleaching of radiolyzed solid HCN with light of different wavelengths (236–600 nm) were studied by ESR and optical spectroscopy. Two bands at 270 and 290 nm in the optical spectrum were attributed to the presence of H₂C=N and HC=NH radicals, respectively (the molar absorption coefficients are k ₂₇₀ 2.7 × 10²l mol^–1cm^–1and k ₂₉₀ 1.5 × 10²l mol^–1cm^–1, respectively). Structureless broad bands with maximums at 313 and 465 nm, which were detected after the exposure of a sample to light with 300 nm, can belong to the cyanide ions (CN^–) and H₂C=N⁺cations (the molar absorption coefficients of the ions are k _ion= (0.4–1.0) × 10²l mol^–1cm^–1). In the photobleaching of -irradiated HCN ( = 236–280 nm), H₂C=N⁺radicals were additionally formed by the photoinduced reaction of electron transfer from the CN^–anion to the H₂C=N⁺cation. The amount of these radicals generated in the course of photobleaching is several times greater than that of the same radicals formed in the radiolysis via hydrogen atom addition to the multiple bond of HCN molecules.     

Solvent extraction and spectrophotometric including graphite furnace atomic absorption determination of molybdenum in the environment

A selective and sensitive method for the extraction and microgram determination of molybdenum (VI) with hydroxamic acid as yellow molybdenum-hydroxamate complex from acidic medium is described. The molybdenum-PCPPSAHA complex has _max 388 nm, molar absorptivity 5.0 × 10³l mol^–1 cm^–1. The system obeys Beer's law in the range of 1–28 g/ml of molybdenum(VI). Sandell's sensitivity is 0.0192 g cm² and stoichiometry of the complex is 12, molybdenum: PCPPSAHA while mixed complex molybdenum-PCPPSAHA-morin has _max 400 nm and molar absorptivity 5.9 × 10³lmo1^–1 cm^–1 and stoichiometry of the complex is 121.The molybdenum is determined by graphite furnace atomic absorption spectrophotometry after directly pipetted the extract into the furnace which increases the sensitivity 20 fold.     

Reaction of H2PtCl6 with 18-crown-6 and dibenzo-18-crown-6 in 1,2-dichloroethane and acetonitrile

Compounds of the compositions [2(18-crown-6)6(H₂O)2(C₂H₄Cl₂){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], [4(18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)(Pt₂Cl₁₀)^2–], [(dibenzo-18-crown-6)6(H₂O){Pt²⁺(C₂H₄)}(Pt₂Cl₁₀)^2–], and [4(dibenzo-18-crown-6)2(OH₃)⁺2(OH₂)2(NH₃)Pt₂Cl₁₀)^2–] were prepared by reactions of H₂PtCl₆ with 18-crown-6 and dibenzo-18-crown-6.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1593–1599.Original Russian Text Copyright © 2004 by Guseva, Busygina, Khasanshin, Polovnyak, Yarkova, Yusupov.This revised version was published online in April 2005 with a corrected cover date.     

Halogenation of π-cyclopentadienyltricarbonylrhenium and π-cyclopentadienyl(triphenylphosphine)dicarbonylrhenium

Conclusions The following previously unknown rhenium semicoordinaticn compounds were synthesized: [-C₅H₅Re(CO)₂PPh₃Cl]⁺Cl^–, [-C₅H₅Re(CO)₃Cl]⁺Cl^–, [-C₅-H₅Re(CO)₂PPh₃Cl]⁺Be₄, [-C₅H₅Re(CO)Cl₂]⁺ [Re(CO)₄Cl₂]^–, and -C₅H₅Re(CO)₂I₂, the latter of which was separated into the cis and trans isomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimlcheskaya, No. 2, pp. 408–413, February, 1981.The authors express their gratitude to V. F. Sizom, P. V. Petrovskii, and B. V. Lokshin for taking the mass, IR, and PMR spectra.     

Structure and configuration of a new diterpenoid lactone fromLagochilus hirsutissimus

The epigeal part of the plantLagochilus hirsutissimus has yielded a new diterpenoid lactone — lagohirsidin, C₂₂H₃₄O₅, mp 144–145°C, [] _D ²² – 17.5° (c 1; ethanol). Reduction with LiAlH₄ has yielded a diol C₂₂H₃₈O₅, mp 165–166°C [] _D ²⁰ –1.2 (c 0.6; ethanol). Acid hydrolysis of the diol has led to the formation of lagochilin, C₂₀H₃₆O₅, mp 167–168°C, [] _D ²⁰ –3.9° (c 1; ethanol). The synthesis of lagohirsidin from lagochilin has been effected.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 788–792, November–December, 1979.     

Solvation of ions. Part XXIX. Ionic conductances in acetonitrile-water and pyridine-water mixtures

The limiting conductance of various salts of Na⁺, Ag⁺, Cu⁺, Cu²⁺ and Ph₄As⁺ in acetonitrile-water (AN-H₂O) and pyridine-water (Py–H₂O) mixtures are reported. Single ion values are calculated for AN-H₂O mixtures using the TATB assumption [_o(Ph ₄ As ⁺) = _o(Ph ₄ B ^–)]. The trends observed for the limiting Walden products (_o) of the electrolytes and individual ions are discussed in terms of specific ion-solvent interactions and the structural effects of the solvent mixtures.Deceased, August 30, 1982.     

Triterpene glycosides of alfalfa. III. Medicoside I

On the basis of chemical transformations and with the aid of physicochemical results, the structure of glycoside I isolated from the roots of the plantMedicago sativa has been established as hederagin 3-O-[O--L-arabinopyranosyl-(1 2)--D-glucopyranosyl-(1 2)--L-arabinopyranoside] 28-O--D-glucopyranoside. Compound (I), C₅₂H₈₄O₂₂, mp 210–212°C, [] _D ²¹ +38.4° (c 1.48; methanol). Acid hydrolysis of (I) led to hederogenin (II) — C₃₀H₄₈O₄, mp 326–330°C, [] _D ²³ +84.2° (c 0.19; pyridine. The Hakomorimethylation of glycoside (I) yielded the permethylate (IV) — C₆₅H₁₁O₂₂ [] _D ²³ +41.6° (c 1.79; methanol). The GLC analysis of the products of the methanolysis of compound (IV) showed the presence of 3,4,6-tri-O-methyl-D-glucopyranose, 2,3,4,6-tetra-O-methyl-D-glucopyranose, 3,4-di-O-methyl-L-O-arabinopyranose, and 2,3,4-tri-o-methyl-L-arabinopyranose. The alkaline hydrolysis of glycoside I gave compound (III) with mp 230–233°C, [] _D ²¹ +35.2° (c 0.21; methanol), which was identified as medicoside C. Details of the PMR spectrum are given for compound (IV) and of the IR spectrum for compound (I).Institute of the Chemistry of Plant Substances of the Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–610, September–October, 1986.     

Phytoecdysones ofSilene praemixta. II. Premixisterone

The structure of premixisterone (I) — a new ecdysteroid fromS. praemixta M. Pop. (Caryophyllaceae) — has been established. Compound (I) has the composition C₂₇H₄₄O₅, mp 110–112°C (from C₂H₅OH + H₂O), [] _D ²⁴ 0 ± 4° (c 0.85; MeOH), 202 nm (log 3.35), _max ^KBr 3415 cm^–1 (OH), 1710 cm^–1 (C=0), and does not contain the ⁷-6-keto grouping that is characteristic of natural ecdysteroids. The acetylation of (I) with (CH₃CO)₂ in Py gave the amorphous 3,22-diacetylpremixisterone (II), C₂₁H₄₈O₇. Compound (I) has the structure of 3,14,22R,25-tetrahydroxy-5-cholest-8-en-6-one. The IR, PMR, and mass spectra of (I) and (II) are given.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 797–799, November–December, 1979.     

Enthalpies of formation and O-O and C-O bond strengths in polyoxides RO x R′ and RO x

Bond strengths in RO-OOR, ROO-OH, and ROO-OOR (R, R = H, Me, Et, and Bu) molecules, calculated by the semiempirical quantum-chemical methods, were used to determine the enthalpies of formation of polyoxides RO _x R (x = 3, 4) and related radicals and the bond strengths (D/kcal mol^–1) in these molecules:D(ROOO-OR) = 33.2±0.9,D(ROOO-OH) = 37.5±0.7,D(R-O _x R) = 76.0±1.2,D(H-000) = 58.6,D(R-000) = 42.8±0.8. A new value of Benson's polyoxide thermochemical increment, _f H°[O-(O)₂] = 11.1±1.0 kcal mol^–1, was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2190–2193, September, 1996.     

Coordination chemistry of alkali and alkaline earth cations: Synthesis and crystal structure of potassium(benzo-15-crown-5)2 [3,5-dinitrobenzoate(3,5-dinitrobenzoic acid)2]

The interaction of K(35-Dnb) (35-Dnb=3,5-dinitrobenzoate) with benzo-15-crown-5 (B15C5) in ethanol yields a charge-separated sandwich structured complex [K(B15C5)₂]⁺[35-Dnb(35-DnbH)₂]^– even when equimolar amounts of reactants were used and no external 35-DnbH was added to the reaction mixture. The complex (KC₄₉H₅₁O₂₈N₆, FW=1211.1), is monoclinic,P2₁/c,a=11.063(2),b=10.680(1),c=46.548(8) Å, =91.629(2)⁰,Z=4,D ₀=1.485 g/cm³,D _c=1.468 g/cm³, CuK =1.5418 Å, =17.01 cm^–1, 2<130⁰,F(000)=2520,T=298 K. FinalR for the 6618 observed reflections was 0.071. In the sandwich moiety, the K⁺ is 10-coordinated through all the oxygens of the crown molecules (K⁺–O, 2.76–3.11 Å). The 35-Dnb anion lies 5.3 Å below the lower crown mean plane and is charge separated with respect to K⁺ (K⁺–O^–>7 Å) but undergoes strong hydrogen bonding (2.59 and 2.49 Å) through each carboxylate oxygen with the carboxylic protons of two separate 35-DnbH molecules. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82014 (52 pages).     

Equilibrium Particle Distribution in the Disperse System with Coagulation and Aggregate Disintegration

Kinetic equations were formulated, which describe coagulation–fragmentation process in a low concentrated suspension flow at a low shear rate. In such a system dispersed phase divided into fine and coarse fractions as the system is brought to equilibrium. Kinetic equations of two-fraction model were formulated. An approximate solution and, in one particular case, the exact solution of these equations were obtained for the equilibrium state. Detailed analysis of equilibrium particle distribution over the mass m was performed for an exponential coagulation kernel = ₀ m and an degenerated disintegration kernel = ₁₂, in which the disintegration frequency is an exponential function of aggregate mass ₁ = ₀ m ⁺ , and the probability of the fragment detachment from an aggregate is independent ofm and decreases exponentially with an increase in mass of a fragment: ₂ = ₀ ^–1exp(–/₀). The equilibrium distribution was shown to exist only at > 0, and in particular, it is described at = = 1 by the f() = ₀₀ ^–1exp(–/₀) and F(m) = Cx ^–1(x + 1)^{2 – 1} e ^–x functions for the particles of fine and coarse fractions (x = m/m ₀, = m ₀/₀, m ₀ and ₀ are the characteristic masses of coarse and fine fractions, respectively). The particle distribution for the fine fraction at 1 is well approximated by the Gaussian distribution exp[–(m – m ₀)²/(4^–1 m ₀₀)].     

1,5-bis-(2,3-dihydroxy-phenylmethylene)-thiocarbohydrazone as reagent for the spectrofluorimetric determination of nanogram amounts of gallium

A method is developed for the spectrofluorimetric determination of nanogram amounts of gallium using 1,5-bis-(2,3-dihydroxy-phenylmethylene)-thiocarbohydrazone in a 60% (v/v) ethanol-water medium phthalate buffered to pH* 3.5 (_ex 400 nm, _em 493 nm, corrected), which allows the determination of 20–100 and 120–600 g/ml with 1.32 and 0.80 as relative error, respectively, and 5.1 ng·ml^–1 as detection limit. Interferences have been evaluated and the method applied to the determination of gallium in samples of bovine liver, heart and kidney.     

The Spontaneous Fission Decay Constant of 238U Using SSNTD

This work reports the results of 5 measurements of the ²³⁸U decay constant for spontaneous fission, _f carried out using solid state nuclear track detectors (SSNTD), resulting in a mean value of _f = (8.35±0.24)· 10^–17 y^–1. The neutron fluence of the irradiations needed for these measurements were monitored with thin films of natural uranium.     

Low-spin excitations of quasi-one-dimensional polyacetylene chains in Hartree-Fock models

In the -electron approximation taking into account Coulomb repulsion and electron correlation, we have calculated the excitation energy _s of the state with spin s=1, 2, 3 in long polyacetylene chains. From numerical calculations, we have established the dependence _s=(2s–1)₁, which is satisfactorily satisfied for the different wave functions used (from the unrestricted and two variants of the extended Hartree-Fock method). For some of the solutions, localization of the excitation in 2s–1 fragments of the chain is characteristic, which indicates the possibility of interpreting it in terms of a soliton.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 716–719, November–December, 1990.     

Crystallite sizes and paracrystalline lattice distortions in drawn hard elastic polypropylene

Summary The paracrystalline lattice distortions and the mosaic crystallite sizeD ₀₀₁ are constant at all draw ratios ( =1 ... 2,3) of a hard elastic polypropylene foil. The lateral crystallite sizes decrease sharply (but not much) at a small draw ratio and slow to higher .

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Zusammenfassung Beim Verstrecken einer hartelastischen Polypropylen-Folie (Verstreckgrade =1 ... 2,3) bleiben die parakristallinen Gitterstörungen und die MosaikkristallitgrößeD ₀₀₁ konstant. Die lateralen Kristallitgrößen nehmen bei kleinem A steil, aber wenig, ab und verringern sich dann langsam weiter mit wachsendem .

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With 2 figures     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the <Emphasis Type="Italic">Sonogashira</Emphasis> Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

Summary. The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.