The observation of fine-structure transitions in the LMR spectrum of the SeD radical at 5.6 μm

Magnetic and electric dipole transitions between the ²Π_{$\text{1}\text{2}$} and ²Π_{$\text{3}\text{2}$} components of the ground state of SeD have been observed at 1770 cm^?1 in an LMR experiment using a CO laser. The measurements have been combined with other data from the EPR and far-infrared LMR spectra to determine parameters in the effective hamiltonian. A combination of these results with the analogous ones for SeH provides a determination of fundamental parameters relating to the spin-orbit and spin-rotation interactions.     

Determination of the radon diffusion coefficient and radon exhalation rate in Moroccan quaternary samples using the SSNTD technique

Measurements have been made of radon (²²²Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq^.m^-2.h^-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09)^.10^-6 m^2.s^-1 to (4.3±0.36)^.10^-6 m^2.s^-1. Furthermore, the correlation between ²²²Rn diffusion coefficient and porosity are also discussed.     

Spectra and structure of silicon compounds. XVII Raman and infrared spectra and vibrational assignment for hexamethyldisilane and ab initio calculations for disilane and hexamethyldisilane

The IR spectra of gaseous and solid hexamethyldisilane between 4000 and 25 cm⁻¹ and the far-IR spectrum of the liquids from 450 to 25 cm⁻¹ have been recorded. The Raman spectra have been recorded from 3500 to 10 cm⁻¹ for all three physical phases. Assisted by ab initio calculations, the vibrational spectrum of hexamethyldisilane has been assigned under D_3d symmetry and the results of a normal coordinate analysis are discussed. No spectral features indicative of free internal rotation have been observed. Gradient ab initio calculations have been carried out for the disilane and hexamethyldisilane molecules using different types of basis sets. The structural parameters, rotational constants, unscaled and scaled frequencies and harmonic force constants have been reported for both disilane and hexamethyldisilane.     

Fe(III)与2,3-二羟基苯磺酸钠配位反应的动力学研究

[H⁺]在0.01～0.70 mol•L^－1范围内, 离子强度为1.00 mol•L^－1, [Fe(III)]>>[配体]、[H⁺]>>[配体]的条件下, 研究了Fe(III)与2,3-二羟基苯磺酸钠(Tiron)的配位反应. 发现当[H⁺]≤3.00×10^－2 mol•L^－1时, [Fe(III)]²对反应速率有明显的贡献. 求得了相关反应的动力学参数, 从而揭示了FeOH²⁺和与Tiron配位的解离反应途径及的缔合反应机制, 并提出了该配位反应的可能机理.     

Activation of the aromatic system by the SO2CF3 group: Kinetics study and structure–reactivity relationships

The rate constants for the reaction of 2,6‐bis(trifluoromethanesulfonyl)‐4‐nitroanisole with some substituted anilines have been measured by spectrophotometric methods in methanol at various temperatures. The data are consistent with the S_NAr mechanism. The effect of substituents on the rate of reaction has been examined. Good linear relationships were obtained from the plots of log k₁ against Hammett σ_para constants values at all temperature with negative ρ values (?1.68 to ?1.11). Activation parameters Δ^≠H varied from 41.6 to 54.3 kJ mol^?1 and Δ^≠S from ?142.7 to ?114.6 J mol^?1 K^?1. The δΔ^≠H and δΔ^≠S reaction constants were determined from the dependence of Δ^≠H and Δ^≠S activation parameters on the σ substituent constants, by analogy with the Hammett equation. A plot of Δ^≠H versus Δ^≠S for the reaction gave good straight line with 177°C isokinetic temperature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 203–210, 2010     

Synthesis, spectral description, and lipophilicity parameters determination of phenylcarbamic acid derivatives with integrated N-phenylpiperazine moiety in the structure

The phenylcarbamic acid derivatives with N-phenylpiperazine moiety in the molecule have been prepared. The structure has been confirmed by elemental analysis, IR, ¹H NMR, and mass spectral data. For the prepared set of the compounds the lipophilicity parameters have been determined. The experimentally obtained lipophilicity parameters have been correlated with theoretical entries obtained by different computer programs based on the neural network and fragmental methods.     

Structure and electron paramagnetic resonance parameters of the manganese site of concanavalin A studied by density functional methods

The EPR parameters of the manganese site in the saccharide-binding protein concanavalin A have been studied by density functional methods, with an emphasis on metal (⁵⁵Mn) and ligand (¹H and ¹⁷O) hyperfine couplings, in comparison with high-field EPR and ENDOR data. Results for gradient-corrected and hybrid functionals with different exact-exchange admixture have been compared with experiment for the ⁵⁵Mn and the ¹H ligand hyperfine coupling and have been predicted for ¹⁷O hyperfine coupling based on comparison with experiment for the related [Mn(H₂O)₆]²⁺. Appreciable exact-exchange admixture in the hybrid functional is needed to obtain an adequate spin-density distribution and thus near-quantitative agreement with experimental EPR parameters. The common use of experimental proton hyperfine coupling tensors together with the point-dipole approximation for determination of bond lengths is evaluated by explicit calculations.     

Electrochemical studies of the tetrabutyl- and tetramethyl-ammonium ion transfer across the water-1,2-dichloroethane interface: A comparison with the water—nitrobenzene interface

The results of electrochemical studies on the reaction of tetrabutyl- and tetramethylammonium (TBA⁺ and TMA⁺) ion transfer from water to 1,2-dichloroethane are presented in this paper and are compared with se of the water—nitrobenzene interface. The TMA⁺ ion transfer has been studied by the chronopotentiometric cyclic voltammetry methods and that of the TBA⁺ ion by the chronopotentiometric method only.It has been found that the reactions are diffusion controlled over the current density range up to about 1O μA cm^?2 and at polarization rates up to 0.15V s^?1. Diffusion coefficients of the studied ions have been detemined, as well as their formal potentials with respect to an ion-selective tetrabutylammonium electrode to a partition electrode containing tetraethylammonium picrate whose potential is close to zero. In additon, kinetic parameters of the transfer reaction have been determined for the tetrabutylammonium ion from data obtained at current densities over 10 μA cm^?2 (irreversible range).     

39K NMR spectra of the powder and single crystal of potassium titanyl phosphate

The powder and single crystal of potassium titanyl phosphate KTiO(PO₄) have been studied by ³⁹K NMR. The quadrupole coupling and ³⁹K isotropic chemical shift parameters have been calculated. The number of formula units in the unit cell of potassium titanyl phosphate is suggested to be equal to the number of magnetically nonequivalent positions of potassium atoms in the lattice.     

Thermal properties and interactions of l-proline in aqueous solutions of NaCl or KCl at different temperatures

The enthalpies of solution of l-proline in aqueous electrolyte solutions within the electrolyte molality range up to 4.9 mol kg^?1 of NaCl and up to 4.0 mol kg^?1 of KCl at 288, 298 and 313 K have been measured by the calorimetric method. Enthalpies of transfer of l-proline from water to aqueous electrolyte solutions up to saturation have been derived at 273–348 K. The enthalpic and heat capacity parameters of pair and triplet interaction of l-proline with electrolyte in water have been evaluated. Enthalpic parameters of pair interaction at 298 K have been compared to similar parameters for glycine and l-alanine. The temperature changes of reduced enthalpy, and also the change of entropy and reduced Gibbs energy of transfer of l-proline from water to aqueous electrolyte solution at temperature rise from 273 to 323 K have been determined. It has been shown that the entropy–enthalpy compensation takes place for transfer processes.     

FT-Raman and infrared spectra,r0 structural parameters,ab initio calculations and vibrational assignment for nitryl chloride

The FT-Raman spectra (2000-30 cm⁻¹) of liquid and solid nitryl chloride, ClNO₂, along with the infrared spectra (2000-80 cm⁻¹) of the gas and solid have been recorded. All six fundamentals are confidently identified and the potential energy distributions determined from the force fields obtained from ab initio calculations. Several different basis sets have been utilized to determine the harmonic frequencies and force constants which are compared to the previously reported valence force constants. Structural parameters have been calculated with these basis sets including electron correlation with MP2, MP3 and MP4 perturbation. The calculated equilibrium structural parameters are compared to the experimental r₀ structural parameters. The spectra of the solid indicate that there are at least two molecules per primitive cell. All of these results are compared to the corresponding quantities for some similar molecules.     

Rotational spectra and hyperfine interactions of the mono 17O substituted ozones

The rotational spectra of ¹⁷O¹⁶O¹⁶O and ¹⁶O¹⁷O¹⁶O have been observed. The hyperfine structure has been analyzed to give the ¹⁷O quadrupole coupling and spin-rotation tensors for both species. Preliminary values of the molecular parameters are given.     

Structure,vibrational assignment,normal coordinate analysis,and ab initio calculations of methylisocyanate

The infrared (3200-30 cm⁻¹) and Raman (3200-10 cm⁻¹) spectra of gaseous and solid methylisocyanate, CH3NCO, have been recorded. Additionally, the Raman spectrum of the liquid has been obtained and qualitative depolarization ratios have been measured. The CNC bend has been observed in the far infrared and low frequency Raman spectra of the gas at approximately 172 cm⁻¹. An additional far infrared band at ≈50 cm⁻¹ has tentatively been assigned as the methyl torsional mode, although it could be due to the Δν = 1, Δl = ± 1 transitions of the CNC bending mode. A complete assignment of the vibrational fundamentals is proposed. The structural parameters, force constants, and vibrational frequencies have been determined from ab initio Hartree—Fock gradient calculations using the 6-31G* basis set. Additionally, structural parameters have been obtained with the 6-311 + + G** basis set with electron correlation at the MP2 level which are compared to those obtained from the microwave data and electron diffraction study. These results are compared with the corresponding quantities obtained for similar molecules.     

State multipoles and Stokes parameters for the 51,3 D 2 excitation of cadmium

Relativistic distorted-wave calculations have been performed for the excitation of the 5^1,3 D ₂ state from the ground state of cadmium by polarised and un-polarised electrons. A full set of state multipoles of experi-mental interest have been obtained for 20 and 40 eV collision energies. From these results we have calculated the Stokes parameters of the light emitted in the decay to the relevant P states.     

Magnetic circular dichroism and absorption spectra of the mononegative and dinegative ions of [16] annulene

The magnetic circular dichroism (MCD) and absorption spectra of the mononegative and dinegative ions of [16] annulene have been measured in the 16000–30000 cm^?1 region. The results are interpreted using a PPP molecular orbital calculation. It is found that the D_4h symmetry, using Slater type atomic orbitals excellent agreement between experiment and calculations is obtained. The excited ²E_g and ¹E_u states of the mono- and dinegative ions have experimental averaged angular monomenta of 1.0 h and 2.3 h respectively and we conclude to planar ring structures for the ions. Variations in the parameters for the PPP calculations, i.e. B, do not influence the MCD values to any great extent.In addition, from temperature dependent measurements between 20°C and ?150°C, the thermodynamic parameters ΔH and ΔS for the equilibrium observed between molecule and ions in solution have been determined.     

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Amino acids have been used as catalysts for the study of kinetic of enolisation of m-Methylacetophenone, in which iodination has been the chosen method. Several parameters like effect of ketone concentration, effect of dielectric constant, effect of catalysts etc. have been investigated for their effect on enolisation kinetics. The study is focused on β-alanine, dl-alanine, l-alanine and Glycine for their effects on the rate. The order of the rate constants obtained has been found to be in the order of increasing dipole moments of the amino acids i.e. l-alanine < Glycine < dl-alanine < β-alanine. With an increase in the temperature from 323 K to 338 K, an increase in the rate was from 1.3 to 2.12 mol^?1 min^?1. The ongoing reaction was found to be bimolecular in nature. The values of different thermodynamic parameters like Entropy (ΔS^≠), Enthalpy (ΔH^≠), Energy of activation (ΔEa) and Gibbs free energy (ΔF^≠) were found to be 6.20 e.u., 24.74 cal mol^?1, 25.20 k cal mol^?1 and 24.54 cal mol^?1 respectively.     

INDO Investigation of the halogen N.Q.R. frequencies and 14N nuclear quadrupole coupling constants of halothiophenes and halopyridines

The ³⁵Cl, ⁷⁹Br, and ¹²⁷I N.Q.R. frequencies of a number of halothiophenes and halopyridines and the ¹⁴N nuclear quadrupole coupling constants of halopyridines have been determined in terms of the Kaplansky-Whitehead theory with the INDO MO approximations using a consistent set of atomic parameters derived from SCF Hartree-Fock calculations. The theoretical spectral properties are in satisfactory overall agreement with experiment. This result supports the validity of using the above method to provide reliable predictions of N.Q.R. parameters for heteroaromatic systems.This work was carried out with the support of the Consiglio Nazionale delle Ricerche (C.N.R.) of Italy.     

Thermodynamic excess properties of alkanol + amine mixtures and application of the ERAS model

New experimental data of the molar excess volume V ^E of the mixtures ethanol/n-butylamine, heptanol/n-butylamine, n-propanol/dibutylamine have been obtained using the technique of the vibrating tube densitometer. Together with the data for the molar excess enthalpy H ^E from the literature, the V ^E data have been used for testing the applicability of the socalled ERAS model which accounts for hydrogen bonding effects as well as for free volume effects in associating mixtures. The results obtained by adjusting the model parameters reveal a strong cross association between the unlike molecules in the mixture resulting from strong negative values for the hydrogen bonding energy and the hydrogen bonding volume.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60^th birthday, Clermont-Ferrand, France, 17–18 May 1990.     

Influence of metal ions on the activity and stability of the glucose isomerase from Streptomyces atratus

The influence of a number of bivalent metals on the activity ofStreptomyces atratus glucose isomerase has been studied. Mg²⁺ ions are activators and Co²⁺ ions are stabilizers of the glucose isomerase activity. The effective kinetic parameters for the action of the enzyme have been determined.Institute of Microbiology, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 838–842, November–December, 1991.     

Tunable diode laser measurements of N2- and O2-pressure broadening and pressure-induced shifts for 16O12C32S transitions in the ν3 band

Nitrogen and oxygen pressure broadening and pressure-induced shift coefficients for 42 transitions of ¹⁶O¹²C³²S with quantum number m from −25 to 49 in the P and R branches of the ν₃ band at 2062 cm⁻¹ have been measured at room temperature using a high-resolution tunable diode laser spectrometer. Air-broadening and shift parameters have also been calculated from the N₂ and O₂ measurements. The dependence of the broadening and shifting on rotational quantum number is discussed. The results are compared to previous measurements in the ν₁ and 2ν₃ bands and to the parameters for the ν₃ band that are reported in the HITRAN database.