Stereoisomerism of N-(1-Propenyl)thiobenzamide

A prototropic rearrangement of N-prop-2-enylbenzocarbothioamide afforded two stereoisomeric N-prop-1-enylbenzocarbothioamides (IIa, b) isolated as individual compounds. The stereoisomerism is due to hindered rotation around thioamide bond C(S)-N and also to -diastereoisomerism. The configuration of the isolated isomers was investigated by IR spectroscopy, AM1 and PM3 methods. In the molecules occurs the p,-conjugation with participation of nitrogen atom and multiple bonds resulting in formation of a united delocalized MO in the planar fragment C(S)-NC = C.     

Vinyl Ethers Containing an Epoxy Group: XXI. Synthesis and Acid-Catalyzed Cyclization of 1-[ω-(Vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanols- A Simple Route to 2-Propynyloxymethyl-Substituted Cyclic Polyethers

Base-catalyzed reaction of 2-[-(vinyloxy)alkoxy]methyloxiranes with 2-propynyl alcohol (3 wt % of t-BuOK, 60-85°C, 3-12 h) afforded first reperesentatives of the 1-[-(vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanol series in up to 99% yield. Treatment of 1-[2-(vinyloxy)ethoxy]- and 1-[2-(vinyloxy)ethoxyethoxy]-3-(2-propynyloxy)-2-propanols with trifluoroacetic acid (0.5 wt. %) in dry diethyl ether resulted in cyclization with formation of up to 96% of (2-methyl-1,3,6-trioxocan-4-yl)methyl- and (2-methyl-1,3,6,9-tetraoxacycloundecan-4-yl)methyl 2-propynyl ethers.     

NMR spectral study of two crystalline modifications of lithium metaborate,LiBO2

⁷Li and¹¹B NMR spectral parameters were obtained for the two structural modifications of lithium metaborate. We first studied the high-temperature -form of LiBO₂, _iso(¹¹ B) 0, e²qQ/h(¹¹B)=42.5±2.0 kHz, e²qQ/h(⁷Li)=155±5 kHz. The following values were obtained for monoclinic -LiBO₂ with tricoordination of the boron atom: _iso(¹¹ B) = 16±2, e²qQ/h(⁷Li)=32±10 kHz. The electric field gradient on the⁷Li and¹¹B nuclei in the different crystal positions was discussed.Institute of Silicate Chemistry, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 5, pp. 70–73, September–October, 1989.     

Copper-catalyzed arylation of tetrazole-5-thiones upon convection heating and microwave activation conditions

The arylation of 1-phenyltetrazole-5-thione using a series of iodobenzene derivatives in the presence of cuprous chloride and a ligand such as ethylenediamine. It was shown that the use of microwave activation permitted shortening of the reaction time, increasing yields and simplification of the reaction products isolation.     

Nonempirical quantum-chemical calculation of the electric field gradient at the <Superscript>51</Superscript>V nucleus sites in alkali metavanadates

The electric-field gradient tensor at the vanadium nucleus site was calculated ab initio within a cluster model for chained vanadates XVO₃ (X=Li, Na, K). A comparison with experiment showed that it suffices to consider only small (VO₄)^3? and (V₃O₁₀)^5? clusters in crystals of this type. The calculation scheme stability with respect to increasing cluster size was analyzed.     

Local structure of Fe70Cr15B15 X-ray amorphous alloy

The local atomic and magnetic structure of Fe₇₀Cr₁₅B₁₅ X-ray amorphous alloy is studied by means of ¹¹B nuclear magnetic resonance (NMR) and ⁵⁷Fe Mössbauer spectroscopy. It is determined that Fe₈₅B₁₅ and Fe₇₀Cr₁₅B₁₅ X-ray amorphous alloys consist of microregions (nanocrystals) with short-range orders of t-Fe₃B and α-Fe phases. It was found out that chromium atoms in the Fe₇₀Cr₁₅B₁₅ X-ray amorphous alloy are evenly distributed in these two nanocrystals, forming t-(Fe,Cr)₃B and α-Fe(Cr) phases.     

Diamagnetic nuclear <Superscript>119</Superscript>Sn probes in the copper chromites CuCr<Subscript>2</Subscript>X<Subscript>4</Subscript> (X = O,S, Se) with a spinel structure

The CuCr₂X₄ (X = O, S, Se) spinel system has been studied by the Mössbauer spectroscopy of the nuclear diamagnetic ¹¹⁹Sn probe at low temperatures in an external magnetic field. The hyperfine magnetic fields H ^Sn induced by paramagnetic ions at tin nuclei in the CuCr₂S₄ and CuCr₂Se₄ chalcogenides have giant values and are somewhat higher than those detected in the CuCr₂O₄ oxide. This behavior is caused by the strong covalence of the chalcogenides, which is supported by the experimentally found isomer shifts. The H ^Sn field is found to be mainly contributed by superexchange 90° interactions in the B-sublattice along the Cr[B]-X-Sn[B] bond chain, whose role increases in the series O-S-Se. In the oxygen CuCr₂O₄ spinel, the partial contributions to the H ^Sn field induced by the Cu²⁺ and Cr³⁺ ions are estimated. The local magnetic structure of the CuCr₂O₄ spinel is refined, and its total magnetization is shown to be directed along the magnetic moment of copper in the A sublattice.     

Meteorological effects in the intensity of muon groups

The data of the experimental study of cosmic ray muon groups using the DEKOR setup for the period of 2004–2007, during which significant changes in the intensity of groups at the Earth’s surface were detected, are analyzed. It was found that these variations are caused by variations of weather conditions (temperature and atmospheric pressure); barometric and temperature coefficients were determined. It turned out that magnitudes of these coefficients for muon groups are significantly higher than available values for singlemuons. Possible physicalmechanismof the effect is discussed. Since muon groups are formed at high altitudes (of the order of several kilometers), the detected effect can be used for monitoring air temperature variations in the upper troposphere.