Hydrogen bonding of aliphatic and aromatic amines in aqueous solution: thermochemistry of solvation

Thermochemistry of hydration of the aliphatic and aromatic amines was studied. Enthalpies of solution at infinite dilution of amines in water were measured using the method of solution calorimetry. A procedure of taking into account the ionization and non-specific hydration of amines in aqueous media was carried out. A method for estimating the enthalpy of hydrogen bonding of amines in aqueous solutions was suggested on the basis of a comparative analysis of the solvation enthalpies of the solutes in water and methanol. The efficiency of this method is confirmed by evaluating the hydrophobic effect enthalpy.     

Luminescence of neodymium-doped yttria

Pulsed cathodoluminescence of Nd³⁺: Y₂O₃ nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd³⁺: Y₂O₃ cubic phase is located at λ₁ ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd³⁺ arise in the spectrum at λ₂ ≈ 750 nm and λ₃ ≈ 720 nm. The emission spectrum of all Nd³⁺: Y₂O₃ materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd³⁺: Y₂O₃ materials is mainly determined by local absorption (self-absorption) of neodymium ions.     

A method to determine the Gibbs energy of specific interactions in solutions. Hydrogen bonding of proton donating solutes in basic solvents

One of two fundamental types of solute–solvent intermolecular interactions are the specific interactions, such as hydrogen bonding complexation between solute and solvent. The Gibbs energy of specific interactions is an important quantity that determines rate and equilibrium constants in solutions, but it is difficult to obtain by direct measurement. We proposed equations allowing to determine the contribution of specific interactions to the Gibbs energy of solvation in nonelectrolyte solutions. Applying it for the case of proton donating solutes with one acidic hydrogen atom dissolved in basic solvents, we obtained the values of the Gibbs energies of 1:1 complexation in pure base. These values have been compared with the Gibbs energies of 1:1 complexation in tetrachloromethane. Most of the hydrogen bonds are found to have the same energy in pure base and in CCl₄, however, some weakly bound complexes seem to become even more weakened in pure base medium. Suggested method is applicable in a general situation when multiple associates of different stoichiometry and structure are formed.     

Highly transparent ceramics with disordered crystal structure

A highly transparent ceramic has been synthesized from Nd³⁺:Y₂O₃ to which 6 mol. % ZrO₂ and 25 mol. % Sc₂O₃ or Lu₂O₃ were added for disordering the crystal structure. Nanopowders with an average particle size of 10–15 nm served as an initial material. They were compacted by the method of uniaxial static pressing combined with ultrasonic action on nanoparticles. The compacting pressure was 200 MPa; the power of the ultrasonic generator was 1.5 kW. It has been shown that the replacement of Y by isovalent Sc and Lu ions and by heterovalent Zr ions reduces the content of pores and the sizes of crystallites. The transparency of the Nd³⁺:Y₂O₃ ceramic with these additives reaches a maximum of 82.2%, and the 40% intensity level spectral band corresponding to the ⁴F_3/2 → ⁴I_11/2 transition widens from 11.4 to 40 nm.     

Variations in the Ozone Concentration in the Stratosphere over Moscow due to Dunamic Processes in the Cold Period of 2015–2016

New data on variations in vertical distribution of stratospheric ozone overMoscow in the cold half-year of 2015–2016 are presented. This period differed significantly from previous winters in a number of stratospheric parameters. The features of these ozone variations are considered and their relation to the stratospheric dynamics is studied. The most significant decrease in the ozone concentration in comparison with average values was observed at the beginning of March, 2016. The development of further significant ozone layer depletion similar to that occurred in spring 2011 was prevented by major sudden stratospheric warming in March 2016.     

1-acetoxyvinyl phosphonates: Facile synthesis via catalytic acylation of dialkyl phosphites

A new and facile method of synthesis of 1-acetoxyvinyl phosphonates ( 2 ) has been found. Dialkyl phosphites react readily with acetic anhydride in acetonitrile solution in the presence of catalysts to produce 2 and acylphosphonates ( 1 ) as a minor product. The most efficient catalysts are metal compounds of variable valency: iron(II), iron(III), and cobalt(II) chlorides. The same compounds catalyze transformation of 1 into 2 in an acetonitrile solution of acetic anhydride.     

A “sodium trap” based on benzo-15-crown-5 with an exocyclic N-(thiophosphoryl)thiourea moiety

For N-(thio)phosphorylthioureas of the common formula RC(S)NHP(X)(OiPr)₂HL^I (R = N-(4′-aminobenzo-15-crown-5), X = S), HL^II (R = N-(4′-aminobenzo-15-crown-5), X = O), HL^III (R = PhNH, X = S), HL^IV (R = PhNH, X = O), and (N,N′-bis-[C(S)NHP(S)(OiPr)₂]₂-1,10-diaza-18-crown-6) H₂L^V, salts LiL^I,III,IV, NaL^I–IV, KL^I–IVM₂L^V (M = Li⁺, Na⁺, K⁺), Ba(L^I,III,IV)₂, and BaL^V have been synthesized and investigated. Compounds NaL^I,II quantitatively drop out as a deposit in ethanol medium, allowing the separation of Na⁺ and K⁺ cations. This effect is not displayed for the other compounds. The crystal structures of HL^III and the solvate of the composition [K(Me₂CO)L^III] have been investigated by X-ray crystallography.     

Catalytic Activity of Pt(II) Complexes in Addition of Tetrachloromethane to Alkenes

Russian Journal of General Chemistry -     

Addition of Tetrachloromethane to Alkenes,Catalyzed by Pt(II) Complexes

Platinum(II) complexes [dichlorobis(triphenylphosphine)platinum(II), dichlorobis(tri-m-tolylphosphine)platinum(II), dichloro(2,9-dimethyl-1,10-N, N′-phenanthroline)platinum(II), etc.] showed catalytic activity in addition of tetrachloromethane across the double bond in 1-hexene, 1-heptene, 1-octene, 1-decene, and cyclohexene. The stability of the platinum catalysts was evaluated by GLC, gas chromatography-mass spectrometry, and ³¹P NMR and IR spectroscopy; the kinetic relationships of the addition reactions were determined. A reaction mechanism involving formation of trichloromethyl radical was suggested. A correlation was revealed for the first time between the catalytic activity of platinum, palladium, and rhodium complexes and the capability of these complexes to generate hexachloroethane.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 778–782.Original Russian Text Copyright © 2005 by Zazybin, Khusnutdinova, Osipova, Solomonov.