Nonempirical calculations of potential-energy surfaces for nucleophilic addition of H− and F− to an acetylene molecule

The minimal energy paths for the nucleophilic addition of a hydride ion (H^–) and a fluoride ion (F^–) to a molecule of acetylene (A) have been calculated with the use of 3–21++G and 3–21+G double basis sets in the framework of the Hartree-Fock-Roothaan method. The values of the total energies of the reactants, transition states, and products have been refined by means of calculations with more complete basis sets [6–31++G// 3–21++G and 6–31++G*//3–21++G for reaction (1); 6–31+G*//3–21+G and 6–31++G**//3–21+G for reaction (2)] and by taking into account the correlation energy for reaction (1) in the framework of the SCEP/6–31++*//3–21++G method. It has been established that the activation energy of reaction (2) is 15.94 kJ/mole lower than that for reaction (1), that reaction (1) is exothermic, and that the enthalpy change accompanying reaction (2) is close to zero. The character of the distribution of the electron density along the minimal energy paths of both reactions has been analyzed, and the differences appearing as a result of the replacement of the soft nucleophile H^– by the harder nucleophile F^– have been ascertained. The results of the calculations have been compared with the results available in the literature for reaction (1).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 149–155, March–April, 1989.     

Water in melts: Raman spectral investigation of the molten Ca(NO3)2·4H2O−KNO3 system

The Raman spectra of molten mixtures of Ca(NO₃)₂\4H₂O–KNO₃ have been examined, covering the concentration range of 0–70 mole% KNO₃. The frequencies in the spectra of the mixtures have been found to change slightly with concentration. Striking variations in the band shapes have been observed in the regions corresponding to the O–H stretching mode (2850–3850 cm^–1) and the v₄-NO ₃ ^– mode (700–750 cm^–). The results are discussed in terms of perturbed quasi-lattice structure for the melt, in which there could be a displacement of water molecules in the first coordination sphere around Ca²⁺ by the NO ₃ ^– ion.     

Distribution studies of metal ions on stannic arsenate in butanol-HNO3 systems: Quantitative separation of Ni−Fe,Ni−Cu,Cd−Hg and Pb−Hg

Summary This paper deals with systematic distribution studies of metal ions on stannic arsenate in butanol-HNO₃ systems. K_d values of metal ions have been determined by the batch process in solvent systems containing varying proportions of butanol and 50% HNO₃. Quantitative binary separations of Ni–Fe, Ni–Cu, Cd–Hg and Pb–Hg have been obtained on the basis of information from the studies.     

Infrared and raman spectra,vibrational assignments,normal coordinate analysis,and ab initio calculations of methyltrifluoromethyldisulfide and bis(trifluoromethyl)disulfide

The infrared and Raman (3500-35 cm^–1) spectra of gaseous and solid methyltrifluoromethyldisulfide, CF₃SSCH₃, and bis(trifluoromethyl)disulfide, CF₃SSCF₃, have been recorded. Additionally, the Raman spectra of the neat liquids have been obtained and qualitative depolarization values have been measured. These vibrational data have been interpreted, for both molecules, on the basis that the C-S-S-C dihedral angle is approximately 90°. Vibrational assignments are given for both molecules and are supported by normal coordinate calculations utilizing ab initio Hartree-Fock gradient calculations with the 3-21G^* basis set to obtain the frequencies for the normal modes and potential energy distributions. The CH₃ and CF₃ torsional modes have been observed at 140 and 48 cm^–1, respectively, for CF₃SSCH₃, from which periodic barriers of 485 cm^–1 (1.39 kcal mol^–1) and 853 cm^–1 (2.44 kcal mol^–1), respectively, have been calculated. Complete equilibrium geometries have been determined for both molecules by ab initio calculations employing both 3–21G and 6–31G basis sets. The structural parameters for bis(trifluoromethyl)disulfide are compared to those suggested from electron diffraction studies. The results are compared to corresponding quantities obtained for some similar molecules.Taken in part from the thesis of M. M. Bergana which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree.     

Osmotic coefficients of dilute aqueous solutions of unsymmetrical cobalt-amine type salts at 0°C

The osmotic coefficients of dilute aqueous solutions of [Co(pn)₃]X₃ [pn=1,2-diaminopropane and X=Cl^–, Br^– and (NO₃)^–] and [Co(tn)₃]X₃ (tn=1,3-diaminopropane and X=Cl^– and Br^–) have been measured from 0.00 to 0.02 mol-kg^–1 at 0°C by the freezing point method. The results have been compared with those obtained from the numerical integration of the Poisson-Boltzmann equation.     

Apparent molal volumes of aqueous solutions of bis-tetraalkylammonium salts at 25°C: Methylene-group contribution to the limiting molal volume

Densities of aqueous solutions of a series of polymethonium chloride and bromide salts (CH₃)₃–N–(CH₂)_n–N–(CH₃)₃X₂ have been measured at 25°C. Apparent molal volumes have been calculated, and methylene-group contributions to the limiting apparent molal volumes °_v have been estimated. Constant values of the methylene-group contribution of 16.5 and 17.0 cm³-mole^–1 were obtained for the bromide and chloride salts, respectively. These values are consistent with methylene-group contributions reported for other series of organic electrolytes.     

First example of the formation of highly ordered supermolecular structures in a series of gibberellin derivatives

The 3-O-palmitate and 3-O-tridecanoate of gibberellin A₃ have been synthesized and monomolecular Langmuir-Blodgett films have been obtained from them.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 793–795, November–December, 1994.     

Calculations of silicooxygen ring vibration frequencies

In the work model calculations of the vibrations of ideally isolated silicooxygen rings (using PM3 method) have been carried out. three-, four-, and six-membered rings have been considered. It has been found that that the three-membered silicooxygen rings are flat and practically undeformed showing D_3h symmetry. The rings of higher number of ring members (i.e. n>3) are deformed to some extent. The deformation reveals itself most significantly in the Si–O–Si bond angles distribution. In the case of all the rings the bridging Si–O–Si bonds are ca. 0.02–0.04 Å shorter than the non-bridging Si–O⁻ bonds. Hypothetical IR spectra for all the rings considered have been also calculated. Analysis of these hypothetical spectra leads to the conclusion that the whole spectrum can be divided into four wavenumbers regions, 1200–1100 cm⁻¹ stretching Si–O(Si) vibrations; 1000–800 cm⁻¹ stretching Si–O⁻ vibrations; 800–600 cm⁻¹; the region in which a band characteristic of silicooxygen rings appears, and below 600 cm⁻¹ bending ⁻O–Si–O⁻ and (Si)O–Si–O(Si). It has been also found that as the number of ring members increases the ‘ring band’ shifts to lower wavenumbers: 725 cm⁻¹ for three-membered rings, 650 cm⁻¹ for four-membered rings and 610 cm⁻¹ for six-membered rings. Calculated spectra have been compared with the experimental spectra of cyclosilicates. They showed good agreement in the 1200–600 cm⁻¹ region. In the experimental spectra as well as in the calculated ones, with increasing the number of ring members the ‘ring band’ shifts towards lower wavenumbers.     

Characterization of manganese–gallium mixed oxide powders

Mn---Ga mixed oxides have been prepared by coprecipitation of the corresponding oxo-hydroxides as powders and have been characterized in relation to their structural and optical properties. The materials have been characterized by XRD, TG-DTA, skeletal IR and UV–visible–NIR spectroscopies. Large solubility of Mn in the diaspore type α-GaOOH oxo-hydroxide has been found. The spinel related structures of hausmannite Mn₃O₄ and of β-gallia present large reciprocal solubilities at least in a metastable form. At high temperature also bixbyite-type α-Mn₂O₃ solid solutions containing up to 20% at. Ga have been observed.     

Activity coefficients of electrolytes from the emf of liquid membrane cells. IV: Revised activity coefficients of lanthanum hexacyanoferrate(III)

Lanthanum ferricyanide is so far the only 3–3 electrolyte whose activity coefficients have been studied carefully; however, the results have been acknowledged to be inconsistent below 1×10^–4 mol-kg^–1. New measurements have been made with an improved cell, proving that the wrong trend was due to chemical interference in the original cell. The new cell makes it possible to reach dilution levels of the order of 4×10^–6 mol-kg^–1. The salt behaves radically unlike Debye-Hückel's predictions, but agrees with other more refined treatments of the hard sphere models without needing any further hypotheses, such as e.g., association. The revised values of the activity coefficients are reported.     

Pulse radiolysis studies on the reactions of 3-pyridinol with oxidizing radicals

Reaction rate constants for the reactions of 3-pyridinol with oxidizing radicals viz. OH, N₃, Br ₂ ^– , Cl ₂ ^– , SO ₄ ^– and O^– have been determined in aqueous solutions at different, pH's. Absorption spectra of the product transient species have been recorded in the 320–600 nm region. In the alkaline region (pH 13) the N₃ reaction product decays in two steps and O^– does not bring about one-electron oxidation. Similarly, at neutral pH, SO ₄ ^– does not cause selective one-electron oxidation of 3-pyridinol.     

Synthetic and modified isoflavonoids XVIII. Synthesis of 7-isopropoxy-substituted analogs of pseudobaptigenin

7-Isopropoxy derivatives of isoflavones have been synthesized from 1,3-benzodioxole, 1,4-benzodioxane, and 1,4-benzodioxepane analogs of pseudobaptigenin. Their structures have been confirmed by PMR.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 365–369, May–June, 1997.     

Synthetic analogs of natural flavolignans IX. Synthesis of 3-amino-substituted analogs of hydnocarpin

New 3-amino-substituted chromones with 1,3-benzodioxan and 1,4-benzodioxan nuclei in position 2 have been synthesized. The structures of the compounds obtained have been confirmed by their PMR spectra.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 178–181, March–April, 1999.     

Analogs of oxytocin with L- and D-pentafluorophenylalanines in the second position

Summary 1. The separation of pentafluorophenylalanine into optical antipodes has been effected.2. Two new analogs of oxytocin — [2-L-pentafluorophenylalanine]oxytocin and [2-D-pentafluorophenylalanine]oxytocin — have been synthesized and their uterotonic activities have been studied.3. It has been shown that donor — acceptor interaction plays a fundamental role in the stimulation of the biological effect.A. A. Zhdanov Leningrad State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 392–398, May–June, 1977.     

Bisindoles. 18. Some electrophilic substitution reactions in the 1,2-di(indol-5-yl)ethane series

A quantum-chemical calculation has been made and the laws of the electron-density distribution in the molecule of 1,2-di(indol-5-yl)ethane have been determined. The electrophilic substitution reactions most characteristic for it have been studied.For communications 15–17, see [1–3].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–77, January, 1984.     

Raman and Infrared Spectra, Ab Initio Calculations, Normal Coordinate Analysis, and Conformational Stability of 2-Methoxypropene

The Raman (3500–40 cm^–1) and infrared (3500–70 cm^–1) spectra of gaseous and solid 2-methoxypropene, CH₃O(CH₃)C=CH₂, and the isotopomers, CD₃O(CH₃)C=CH₂ and CH₃O(CD₃)C=CD₂ have been recorded. In addition, the Raman spectra of the liquids have been recorded with qualitative depolarization measurements. All of these data indicate that only one conformer is present in the fluid phases at ambient temperature and this form is the cis conformer, which remains in the solid. Assignments are provided for the fundamentals of all three isotopomers for the cis conformer with C_s symmetry. The far-infrared spectra of all three isotopic species have been recorded at a resolution of 0.1 cm^–1 in the gas and 1.0 cm^–1 in the solid. The parameters of the potential function governing the asymmetric torsion are determined to be V₃ = 1485 ± 9 cm^–1 and V₆ = –55 ± 4 cm^–1 for the d₀ compound, where only two terms were determined, since a second conformer was not evident. The barrier to internal rotation for the methyl group attached to the oxygen atom is 1370 ± 8 cm^–1 and the C—CH₃ barrier is 772 ± 5 cm^–1. Ab initio calculations with full electron correlation have been carried out by the perturbation method to second order to obtain the equilibrium structural parameters, harmonic force constants, fundamental frequencies, infrared intensities, Raman activities, depolarization values, and conformational stability. The predicted values have been compared to the experimental values where appropriate.     

Stereochemistry of the products of the hydrogenation of leucomisin

4-H(4-Me)-3-hetarylcoumarins modified by 1,3-benzodioxolane and 1,4-benzodioxane residues have been synthesized. The structures of the compounds obtained have been confirmed by PMR.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 230–233, March–April, 1994.     

Synthesis and Cytotoxicity of Derivatives of Di(3-indolyl) Selenide

A method has been developed for the synthesis of di(3-indolyl) selenides. From indole and SeO₂. N-Alkyl derivatives of di(3-indolyl) selenide have been obtained in the two-phase system alkyl halide–solid K₂CO₃ (or KOH)–18-crown-6–toluene. It was discovered that N-unsubstituted di(3-indolyl) selenides possess high cytotoxicity on HT-1080 and MG-22A tumor cell lines.     

Synthetic and modified isoflavonoids. XIII. Synthesis of analogues of fujikinin

Analogues of a natural isoflavone glycoside — fujikinin — have been synthesized. Their structures have been confirmed by their PMR spectra.Taras Shevenko Kiev University: KIEN, Karakalpak Division, Academy of Sciences of the Republic of Uzbekistan, Nukus. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 347–351, May–June, 1994.     

Phytoglycolipids of the grape

The qualitative and quantitative compositions of the grape and its component parts — flesh, skin, seeds — have been studied. Ten fractions have been identified, the main ones being cerebrosides and monogalactosyldiglycerides. The compositions of the fatty acids, of the sphingosine bases, of the sterols, and of the carbohydrates of the individual fraction of phytoglycolipids have been determined.Physicochemical Institute of the Academy of Sciences of the Ukrainian SSR, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 296–300, May–June, 1984.