Cardiac glycosides of Cheiranthus allioni. XI

Summary Another three cardiac glycosides have been isolated from the seeds ofCheiranthus allioni hort. One of them has been identified as digifucocellobioside (digitoxigenin 3 -O-[O--D-glycopyranosyl(1 4)-O--D-glucopyranosyl(1 4)-O--D-fucopyranoside]). The two other glycosides, called digitoxigenin gulomethyloside and glucodigigulomethyloside are, respectively, digitoxigenin 3 -O--D-gulomethyloside and digitoxigenin 3 -O-(4-O--D-glucosyl--D-gulomethyloside).For Communication X, see [1].Khar'kov Scientific-Research Institute of Pharmaceutical Chemistry. All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 754–758, November–December, 1975.     

Determination of fluazifop-butyl and fluazifop with the use of disposable solid phase extraction columns for selective clean-up and concentration of Soxhlet soil extracts

Summary An analytical procedure based on the solid phase extraction technology has been developed for the clean-up and concentration of Soxhlet soil extracts containing fluazifop-butyl and fluazifop by the use of a phenyl phase cartridge. No liquid-liquid partition has been used; thus the consumption of organic solvents was limited and the use of chlorinated solvents could be avoided. Quantification has been performed by ion-pair HPLC. Despite the large difference in polarity the recoveries of both the compounds from spiked soil samples between 0.1 and 1 g/g was higher than 90%. The solid-phase adsorption technology resulted in a very effective methodology of clean-up in the case of the polar compound fluazifop, for which a second disposable column with a cyanopropyl phase has been used, and was fairly satisfactory for fluazifop-butyl. The detection limits were less than 0.04 g/g and 0.10 g/g, respectively for fluazifop and fluazifop-butyl.     

Direction of nucleophilic substitution in α, β-unsaturated imino compounds with a donor substituent in the beta position

A mechanism of conversion of -aminovinyl ketones into -aminovinylimines is disclosed. It has been found that in this and a series of other reactions (various conversions of -aminovinyl ketones, -aminovinylimines, and -alkoxyvinylimino salts and their vinyl analogs, cyano compounds, etc.), the intermediate determining the course of the reaction is an ,-unsaturated imino cation. The result of the reaction depends on the site and efficiency of the nucleophilic attack by tautomeric imino salt compounds possessing an unshared electron pair distributed over the various electrophilic sites of the molecule.     

35Cl NQR Studies of the Geometry of Aromatic Imines

The preferred conformation of solidphase R4benzylidene3,4dichloroaniline molecules has been established by nuclear quadrupole resonance (NQR) combined with quantum chemical calculations. The conformational effect of substitutes reported previously is proved. The rotation angle of the plane of the aniline ring with respect to the plane of the azomethine bond is given.     

Ionic Interactions of Calcium Sulfate Dihydrate in Aqueous Sodium Chloride Solutions: Solubilities,Densities, Viscosities,Electrical Conductivities,and Surface Tensions at 35 <Superscript>∘</Superscript>C

The thermodynamic, volumetric, transport, and surface properties, solubilities, densities, viscosities, electrical conductivities, and surface tensions of calcium sulfate dihydrate in aqueous sodium chloride solutions have been measured at 35 C, with a view to determine the ionic interactions that occur in these solutions. The experimental density values have been used to calculate the mean apparent molar volumes of the ternary mixtures. Viscosity values have been analyzed using different empirical equations and the experimental values of the viscosity were combined with conductivity to yield the Walden product. Molar surface energies have been computed using experimental surface tension data. The experimental data have been fitted to polynomial equations by a least-squares analysis to obtain the coefficients and their standard errors. Results have been examined in the light of structure making or structure breaking effects of the various ions present in the solutions.     

Scanning electron microscopic study of an industrial catalyst for ammonia synthesis

The surface topography and elemental composition of the near-surface layers of a reduced passivated catalyst for ammonia synthesis have been studied on a scanning electron microscope in the initial state and after high-temperature oxygen treatment as well as removal of the alkali promoter.

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CA-IB , .

     

New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups

Summary. CD exciton chirality methods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of - and -hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids, the direct esterification of sterically hindered carboxyl groups with 2-naphthol also allows the stereochemical assignment via CD spectroscopy.     

A quantitative model describing physical aging in isotactic polypropylenes

Physical aging of isotactic polypropylenes (homopolymer and random ethylene-propylene copolymer) at room temperature is investigated by low-strain creep, damping measurements, differential scanning calorimetry, and infra-red spectroscopy. Examination of the results suggests that physical aging produces a decrease of the magnitude of the -relaxation (lower glass transition) and an increase of the magnitude and of the relaxation time of the -relaxation (upper glass transition). A model is proposed that accounts for the variations of the fractions of amorphous material which undergo these relaxations. In this model, deformation and increase in the -fraction at the expense of the -fraction are expected to be diffusion processes. The agreement with experimental data is good. Moreover, the -form is shown to be an amorphous phase rich in molecular segments having a helical conformation.     

Crystal Structures of the Inclusion Complexes of β-Cyclodextrin with Aliphatic Monoacids Tridecanoic Acid and (Z)-Tetradec-7-enoic Acid. Formation of [3]Pseudorotaxanes

The structures of the inclusion complexes of beta cyclodextrin with the aliphatic mono-acids tridecanoic acid (1) and (Z)-tetradec-7-enoic acid (2) have been determined at room temperature. Both compounds crystallise in P1, a = 15.654(6) Å, b = 15.650(6) Å, c = 15.937(6) Å, = 101.58(1)°, = 101.59(1)°, = 103.58(1)°, Z = 1, for 1 and a = 15.6259(9) Å, b = 15.623(1) Å, c = 15.935(1) Å, = 101.547(2)°, = 101.555(2)°, = 103.642(2)°, Z = 1, for 2. One molecule of the monoacids threads through two cyclodextrin macrocycles arranged in dimers thus forming [3]pseudorotaxanes. The host dimers are aligned along a channel in order to create a hydrophobic environment for the terminal methyl group of the guest and isolate it from the aqueous environment that surrounds the cyclodextrin dimeric units. The guests exhibit disorder over two orientations resulting in hydrogen bonding between the carboxyl groups of adjacent guest molecules along the channel and formation of carboxylic dimers. This crystal packing differs from that of -CD complexes of homologous dicarboxylic acids.     

New algorithm for nonorthogonal ab initio valence bond calculations II: Subgraph-driven method

The permanent method for nonorthogonal VB calculations is extensively developed, and the so-called subgraph-driven procedure is proposed. To achieve high efficiency, the summation of a huge number of permanents is treated as a whole system, and the intermediate quantities, the contracted-cofactors of various orders, are introduced for the systematic summation. These intermediate quantities can be characterized by pairing graphs of 2n elements (n = 1, 2, ... 1/2N – 2). Some test calculations for systems of up to 20 electrons are performed. The practice shows that this method is highly efficient, and the CPU time increases in a quite moderate way with the increasing number of electrons.On leave from Chemistry Department, Xiamen University, 361005 Xiamen, PR China.     

Cyclohexene skeletal isomerization activity of sepiolites modified with B3+ or Al3+ ions

The effect of sepiolite modification by B³⁺ and Al³⁺ ions on catalytic performance were investigated in cyclohexene skeletal isomerization (CSI) reaction. Catalytic activity to 1- and 3-methylcyclopentenes (1- and 3-MCP) fit the Bassett-Habgood kinetic model for first order processes. These ions induced strong acidity in the sepiolite and the best results (greater activity and selectivity to 1-MCP) were found when the sepiolite was exchanged with an BF₃/methanol solution which contained 3 wt.% of the B³⁺ ion.

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B³⁺ Al³⁺ . 1- 3- - . . - 1-- , BF₃/, 3 . % B³⁺.

     

Über die Reaktion von Pyridylthioharnstoffen mit einigen Acetylen-Verbindungen

Pyridylthioureas were prepared by hydrolysis and decarboxylation of the corresponding N-ethoxycarbonyl-N-pyridylthioureas. Pyridylthioureas reacted with esters of acetylene dicarboxylic acid to form derivatives of thiazolinone (6).     

Reactivity of Cyclohexanol CH Bonds toward the tert-Butylperoxy Radical

The effect of the hydroxy group on the partial rate constants of the reactions of the tert-butylperoxy radical with CH bonds in cyclohexanol at 333 K was studied by the Howard–Ingold method. The overall reaction rate constant increased with decreasing alcohol concentration in chlorobenzene because of complex effects of hydrogen bonds at the steps of chain growth and termination. The hydroxy group activates the -CH bond and deactivates the - and -CH bonds. The reactivity of -CH bonds is close to the reactivity of CH bonds in cyclohexane.     

Theory of bridge-assisted electron transfer in systems with an intermediate link at high temperatures

From solution of the time-dependent wave equation by specifying the (t) function in the form of a linear combination a_i(t)_i+a_d(t)_d+a_j(t)_j (_i, _d, _j are the wave functions corresponding to localization of the electron on the donor, the intermediate link, and the acceptor), we obtain an expression for the electron transfer probability in a system consisting of six components: one direct transfer and five interference components. We have studied the effect of electronic structure and vibrational motion of the components of the system on the probability components. This has allowed us to find the dependence of the electron transfer probability on the ionization potential or the electron affinity of the intermediate link, playing the role of a catalyst or inhibitor of the process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 134–142, March–April, 1989.     

Positron spectroscopy of rehydrated pyrogeneous silica surface

Positron annihilation method has been used for investigating amorphous nonporous pyrogeneous silica of high purity. The influence of water adsorption on the structure of the silanol surface is shown. The effect of swelling, that is an increase of interglobular free volume at intermediate degrees of silica hydration has been observed.     

Reaction of esters of β-tetrahydrofurylpropionic acid and itsα-alkyl derivatives with phosphorus tribromide

Summary The reaction between the esters of-alkyl--tetrahydrofurylpropionic acids and phosphorus tribromide leads to the formation of the esters of 1-alkyl-3, 6-dibromoenanthic acids, which when treated with alkaline agents, are converted to the corresponding 3-alkyl-5-(-bromopropyl)butyrolactones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1670–1671, September, 1965     

Substitution reactions involving organoaluminum compounds

The reaction of ,-dichloro- and ,-diacetoxysulfides with dialkyl-Z-alkenylalanes has been studied; reaction occurs under mild conditions with retention of Z-configuration in the double bond. The reaction represents a stereospecific method for the synthesis of cyclic Z-homoallyl sulfides. The corresponding cycloalkanes and cycloalkenes can be obtained from these Z-homoallylic sulfides by desulfurization with Li in ethylamine or with Raney nickel.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1869–1874, August 1989.     

New asterosaponins from the starfishDismolasterias nipon

Three new glycosides, D₁, D₂, and D₃, have been isolated from the Far Eastern starfishDistolasterias nipon. They have been identified by chemical and physicochemical methods as 5-cholestane÷3,6,8,15,24-pentaol 3,24-di-O--D-xylopyranoside, t-cholest-22-ene-3,6,8,15,24-pentaol 3,24-di-O--D-xylopyranoside (II), and 5-cholestane-3,6,8,15,24-pentaol 24-O--D-glucopyranoside 3-O--D-xylopyranoside (III).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 250–255, March–April, 1987.     

Synthesis of γ-diketo carboxylic acids and their esters

Conclusions We have developed a method of obtaining -diketocarboxylic acids and their esters by acid hydrolysis of esters of-(5-methylfuryl)propionic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 214–215, January, 1968.     

New Approach to Analysis of the Nonlinearity of the Brønsted Relationship: II. An Empirical Procedure Combining the σρ Correlation Method with the Concept of Hard and Soft Acids and Bases,as Applied to Pseudo CH Acids

A comparative systematic analysis of the features of Brönsted behavior of pseudo CH acids(according to Eigen's classification) is made. The analysis is based on combined use of experimental data onpK _a, Ggas, logk _D of CH acids (Ggas is the free energy of acid ionization in the gas phase, logk _D isthe logarithm of the rate constant of hydrogen exchange in a protic solvent). The modified nucleophilicKabachnik constants ^- are applicable to correlations for all the three kinds of acidity of pseudo CH acids. The electrostatic solvation makes an insignificant contribution to variation of pK _a and weakening of the substituent effect in going from the gas phase to dimethyl sulfoxide, and also to differentiation of the kinetic acidity. The coefficient in the Brönsted equation and the ratio between the rate constants in the correlations, which characterize the degree of proton transfer in the reaction transition state, have much in common from the physical viewpoint. The results of correlation analysis, demonstrating intramolecular uniformity of the interactions, are fully consistent with the conclusion made in the previous part of this work about the solvation uniformity of the interactions, resulting in the absence of thermodynamic deviations from the Brönsted relationship.