Investigation of longitudinal vibrations of -O-H groups in chrysotile asbestos by neutron scattering and polarized infrared spectroscopy

The specific features of the vibrational spectra of chrysotile asbestos, which is a natural mineral that represents a system of closely packed tubular fibers with an outer diameter of ∼30 nm, an inside diameter of ∼5 nm, and a length up to a centimeter and more, have been investigated using neutron scattering and polarized infrared spectroscopy. This material can serve as a natural matrix for the preparation of nanostructures by filling channels with various materials.     

Gd<Superscript>3+</Superscript> EPR in solid solutions based on ferroelectric lead germanate

The splitting of the ERP spectrum of a single Gd³⁺ ion into four intense components has been observed in crystals of Pb₅(Ge_{1 − x} Si _x )₃O₁₁ solid solutions, which is caused by the appearance of silicon ions in three nearest germanium spheres. The atomic structure of the observed centers has been determined. The conclusion has been made that silicon mainly substitutes for germanium in oxygen tetrahedra and for one of germanuim atoms in oxygen bitetrahedra, which is based on comparison of the measured ratio of component intensities with the results of the calculation of the concentrations of Gd³⁺ associations with silicon ions.     

Transannular additions of selectfluor and xenon difluoride: regioselectivity and mechanism

The addition of 1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo[2.2.2]octane bis‐tetrafluoroborate (F‐TEDA) to unsaturated systems was modelled computationally at the ab initio levels and studied experimentally. The reaction of olefins with F‐TEDA is driven exclusively by charge transfer and displays the antibonding orbital picture in the transition structure for F‐transfer, similarly to that for the reactions of olefins with F‐radical. In contrast, the electrophilic and concerted fluorinations, respectively with H₂O???F⁺ complex and with F₂, show strong bonding interactions between the fluorine and olefin moieties in the transition structures. The reaction with F‐TEDA involves an initial formation of highly delocalized charge‐transfer complexes in the first step with further low‐barrier (ca 4 kcal) migration of fluorine and is best described as an inner‐sphere electron transfer. This nonelectrophilic mechanism is operative for the transannular addition of F‐TEDA to 3‐methylene‐7‐ethylidenebicyclo[3.3.1]nonane studied experimentally. The addition mode is determined by the formation of a more stable complex via the ethylidene fragment and demonstrates selectivities that differ from conventional electrophilic additions. This mechanistic scenario may be extended to the fluorination with xenon difluoride where similar products are formed in high yields. Copyright © 2010 John Wiley & Sons, Ltd.     

Diffusion and virial coefficient in a mercury-argon gas mixture

Theoretical and experimental data on molecular beams and the mutual diffusion coefficient (MDC) and second virial coefficient (SVC) for an Hg-Ar gas mixture as a representative of the mercuryinert gas family are matched on basis of the Morse potential and the relations of the molecular kinetic theory of rarefied gases. Tables of the MDC and SVC values in the temperature range of 200–2000 K are calculated, and estimates of their accuracy are presented.     

Fluorosulfation of fluoroalkyl halides

The basic characteristics of fluorosulfation of fluoroalkylhalides (effect of the structure of the polyfluoroalkyl, nature of the halogen, acid catalysis, etc.) with halogen fluorosulfates and peroxydisulfuryl difluoride were investigated. A mechanism was proposed for formation of fluorosulfonic acid fluoroalkyl esters based on the experimental and quantum chemical data.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1718–1732, August, 1992.     

Reactions of highly electrophilic polyfluorocarbonyl compounds with primary arylamines

C-Hydroxyalkylation of primary arylamines by highly electrophilic polyfluorocarbonyl compounds results from the direct reaction of the initial reagents and is competitively inhibited by equilibrium N-hydroxyalkylation. The presence of steric hindrances to the formation of N-hydroxyalkylation products and an increase in the ring C-nucleophilicity facilitate the C-hydroxyalkylation reaction.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 383–389, February, 1990.