Isomerization of S-2-hydroxyalkyl esters of cyclic phosphorus thioacids

Conclusions The S-2-hydroxyalkyl esters of cyclic P(V) thioacids, which were obtained by reacting a cyclic phosphorus monothioacid with an alkylene oxide, are converted to the 2-mercaptoalkyl esters of cyclic phosphorus acids independent of the size of the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2594–2596, November, 1980.     

Reinvestigation of the Nazarov cyclization of 1-(3-hydroxypropynyl)cyclododecan-1-ol to bicyclo[10.3.0]pentadec-1(12)-en-13-one

Reinvestigation of the acid-catalyzed cyclization of 1-(3-hydroxypropynyl)cyclododecan-1-ol under the conditions of the Nazarov reaction demonstrated that this conversion yields two isomeric bicyclic ketones, namely, bicyclo[10.3.0]pentadec-1(12)-en-13-one and bicyclo[10.3.0]pentadec-1-en-3-one. The latter compound is thermodynamically less stable. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1325–1327, July, 1997.     

The hydration of hydrophobic substances

A model of the hydration of hydrophobic substances in water is suggested. The models of fluctuation formation of empty cavities in water as a stage of hydration extensively used in the literature were shown to be at variance with experiment. The fundamental role played by the interphase boundary surface was emphasized. On this surface, the successive addition of water molecules with the formation of capsules around hydrophobic molecules occurred. The physical meaning of the Ostwald equation was revealed. This equation characterized the distribution of hydrophobic volatile substances between the gas and aqueous phases. The method of optical probes (hydrophobic aromatic molecules) was used to reveal the synergistic character of autocorrelation of dispersion interactions between water and hydrophobic substance molecules. This synergism was at variance with the Lennard-Jones potential. The synergism (superadditivity) of dispersion attraction forces, which strengthened their directional character, caused the self-organization and enhanced stability of hydration capsules with encapsulated hydrophobic molecules. Computer models were used to show that the spatially directional character of dispersion interactions necessary for the self-organization of hydrated aggregates could be simulated by the molecular mechanics method on the basis of orientational correlation of water molecules and hydrophobic substances in the starting system.     

Synthesis of (o-Carborane-1,2-diyl)dipropanoic Acid and Its Derivatives

Hydrolysis of 1,2-bis(cyanoethyl)-o-carborane easily available by cyanoethylation of o-carborane gives (o-carborane-1,2-diyl)dipropanoic acid. The corresponding acid dichloride, diamide, dianilide, dibenzophenone, and diol were prepared from it by typical procedures.     

The influence of ms-substitution on the properties of 3,3′-bis(dipyrrolylmethenes) and their coordination compounds

We have compared the coordination properties of decamethyl-substituted 3,3′-bis-(dipyrrolylmethenes) (H₂L) with different ms-spacers separating the dipyrrolylmethene domains: methylene -CH₂-, methoxyphenylmethylene -CH(p-C₆H₄OMe)-, and trifluoromethylmethylene -CH(CF₃)-. The stable binuclear homoligand complexes [M₂L₂] are formed in reactions of the ligands with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) acetates. In the cases of all H₂L ligands the thermodynamic constants of the complex formation reactions increase in the following series: Cu(II) < Cd(II) < Hg(II) < Ni(II) < Co(II) < Zn(II). The change in -CH₂- ms-spacer to -CH(p-C₆H₄OMe)- or -CH(CF₃)- results in a decrease in the constant of H₂L complex formation by 1–4 orders of magnitude, the cation being the same. The influence of ms-substitution on the stability and luminescence properties of [M₂L₂] has been discussed.     

Thermal behavior of paramagnetic Gd3+ centers in CsSrCl3

The temperature dependence of the order parameters and the axial initial splitting parameter of Gd³⁺ impurity complexes is measured in the first low-symmetry phase of CsSrCl₃, and the relationship between these parameters is found. The parameters of the thermodynamic potential, which takes into account the interaction of the order parameter with strains, are estimated. The nature of the temperature dependence of the axial initial splitting parameter in the cubic phase is explained. Fiz. Tverd. Tela (St. Petersburg) 41, 2065–2069 (November 1999)     

Neutron-neutron angular correlations in spontaneous fission of <Superscript>252</Superscript>Cf

An experiment has been carried out to study neutron-neutron angular correlations in spontaneous fission of ²⁵²Cf. Angular dependences of the number of neutron-neutron coincidences obtained in the experiment were compared with the results of the Monte Carlo calculations for various neutron detection thresholds in the range 425–1600 keV. It was inferred that 10–11% of the total number of prompt neutrons from ²⁵²Cf (s.f.) in the laboratory system were emitted isotropically and may probably be interpreted as neutrons directly associated with the instant of scission of the nucleus. The analysis allowed their energy distribution to be determined as well. A similar method was also used to describe the angular correlation of prompt neutrons that accompanied the reaction ²³⁵U(n _th ,f).     

Plasma Synthesis and XPS Attestation of Thin-Film Carbon Coatings with Predetermined sp-Hybridization

Physics of Atomic Nuclei - The diversity of carbon materials has allowed them to be used for fundamental and applied research to date. The newest modifications of carbon, such as nanodiamonds,...     

Fast and continuous chemical isolation of short-lived isotopes of Hf,Ta and W as homologs of elements 104, 105 and 106

Some short-lived isotopes of Hf, Ta and W, synthesized at the U-400 cyclotron of JINR-Dubna, have been isolated using a previously elaborated fast continuous method of chemical isolation of element 104 from nuclear reaction products. The products were transported by a NaCl aerosol jet, from the irradiated targets to a separation device in which Hf, Ta and W were isolated by using three coupled ion-exchange columns.