Hyperfine interactions for181Ta nuclei in the laves phases LuFe2 and GdFe2

The hyperfine magnetic fields for¹⁸¹Ta in the cubic (C 15) Laves phases LuFe₂ and GdFe₂ have been measured by the TDPAC method. At 300 K, B_hf=−20.5(4) T for LuFe₂ and +19.0(5) T and +10.2(4) T for the samples of GdFe₂, prepared at normal and high (7.7 GPa) pressure, have been obtained. Temperature dependence of these fields in the range 77–900 K has been also measured.     

Sodium persulfate in solid phase organic synthesis

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1930–1931, August, 1990.     

Structure and dehydration of hydrous tin dioxide xerogel

Hydrous tin dioxide xerogel with the composition SnO2 · 1.75H₂O is built of tin-oxygen-hydroxide fragments. Water molecules (no more than 1 mol) in the grain structure are kept by hydrogen bonds. Xerogel is dehydrated in the range 50–890°C in two stages. Below 123°C, molecular water is removed and the polycondensation of ≡Sn-O(H)-Sn≡ bridge groups occurs. There also takes place the transition of some water molecules from the molecular to hydroxide form as follows: ≡Sn-O-Sn≡ + H₂O → 2≡Sn-O-H. All processes occur within individual grains. Above 123°C, water removal is due to the polycondensation of tin-oxygen groups. As a result, grains are coarsen. After 200°C, their structure is determined as cassiterite coated by tin oxyhydrate.     

Isotopic Study of the Formation of Phenoxazine Derivatives in the Transformations of 3,5-Di-tert-Butylcatechol Adsorbed in Thin SiO2-nTiO2 Layers in the Air

A study was carried out on the isotopic composition of the tetra-tert-butylphenoxazine derivatives formed in the heterophase transformations of 3,5-di-tert-butylcatechol adsorbed on thin SiO2 layers with microscopic traces of Ti and Mn in a nitrogen-oxygen atmosphere enriched with ¹⁵N₂. The formation of isotopically-labeled tetra-tert-butylphenoxazinyl and hydroxytetra-tert-butylphenoxazinyl radicals and tetra-tert-butylphenoxazinone indicated the participation of atmospheric nitrogen in the heterophase catalytic reaction.     

New Opportunities for Duff Reaction

Reaction of 2,4-di-tert-butylphenol with urotropin in conditions of Duff reaction takes an abnormal route and instead of the expected di-tert-butylsalicylaldehyde provides a mixture of N-substituted 3,5-di-tert-butyl-2-hydroxybenzylamines and redox conjugate benzoxazines containing mostly 6,8-di-tert-butyl-3-(3,5-di-tert-butyl-2-hydroxybenzyl)-2H-3,4-dihydrobenz[e][1,3]oxazine. A solvolysis of an individual benzoxazine in the system HO(CH₂)₂OH-H₂O-HCl affords di(3,5-di-tert-butyl-2-hydroxybenzyl)amine, and in AcOH 3,5-di-tert-butylsalicilaldehyde. A mechanism of Duff reaction was suggested involving the formation of a benzoxazine intermediate.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 718–721.Original Russian Text Copyright © 2005 by Belostotskaya, Komissarova, Prokof’eva, Kurkovskaya, Vol’eva.     

Novel 2-alkoxy- and 2-alkylthio-substituted pyrimidines containing 2-(1-methyl-1H-pyrrol-2-yl)vinyl moieties: optical and electrochemical properties

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New Photochromic Spiropyrans with <Emphasis Type="Italic">ortho</Emphasis>-Hydroxyaldimine Substituent

A series of new spiropyrans of indoline series with ortho-hydroxyaldimine substituent has been synthesized, their structure and photochromic properties have been studied. The structure of the obtained compounds was confirmed by the data of 1H NMR and IR spectroscopy and elemental analysis. Photochromic properties of the prepared compounds have been studied. The introduction of ortho-hydroxy group into aldimine fragment of molecule (in the 6 position of the 2H-chromene fragment) has increased the lifetime of merocyanine isomer by 40 times as compared with amino-substituted spiropyran.     

Nucleophilic substitution in dibenz[b,d]iodolium and 11,12-dihydro-10H-dibenz[b,g]iodocinium cations

Treatment of dibenz[b,d]iodolium tetrafluoroborate with NO₂ ^–, Br^–, and N₃ ^– ions gave, along with nucleophilic substitution products, 2-nitro-, 2-bromo-, and 2-azido-2-iodiphenyls, diphenyl, 2-iododiphenyl, and 2,2-diiododiphenyl (products of one electron reduction), whereas 11,12-dihydro-10H-dibenz[b,g]iodocinium tetrafluoroborate underwent nucleophilic substitution with all three nucleophiles to give a single product in each case: 1-(2-nitrophenyl)-, 1-(2-bromophenyl)-, or 1-(2-azidophenyl)-3-(2-iodophenyl)propane.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 405–412, March, 1998.     

The threshold of subharmonic parametric excitation in the bragg gap of a periodic structure

Methods of excitation of the subharmonic whose frequency lies within the forbidden band gap of a periodic structure are discussed. The dependences of threshold values of in-phase pumping on structure parameters are found.