Subsolidus phase relations of ternary oxide systems containing divalent Fe, Mg, or Ni, trivalent Al, Cr, or Fe, and tetravalent Ti are characterized by solid solutions at metal/oxygen ratios , , and . At low temperatures only compounds with cubic or hexagonal close-packed oxygen and uniform oxygen coordination remain stable in the crystal structures NaCl, spinel, ilmenite-α-Al2O3, TiO2. The pseudobrookite phases FeTi2O5, MgTi2O5, Al2TiO5, Fe2TiO5, the V3O5 structure phase Cr2TiO5, and the Andersson phases Cr2Tin?2O2n?1 (n = 4,6,7,8,9) decompose. Additional phases with close-packed oxygen as predicted by a simple structure model for metal/oxygen ratios , , and do not form but presumably are important for nonstoichiometric solid solutions. Most differences between systems containing transition metals and the MgOAl2O3TiO2 system can be attributed to crystal field effects. 相似文献
The heat capacity and heat content LiTiO4 and Li2Ti3O7 have been measured in the temperature range 198—960 K. The lattice and dilation contributions to the heat capacity have been estimated. The standard thermodynamic functions and the high temperature enthalpy and entropy have been derived. The lattice heat capacity of LiTiO4 spinel appears to be consistent with the phonon model put forward by Grimes. 相似文献
An X-ray structure analysis shows that the 5, 18-dimethyl derivative () of the title compound () crystallises from xylene as a 1:1 inclusion compound in which the host molecules adopt propeller-like conformations ( and *) with almost perfect 2 symmetry. Dynamic 1H n.m.r. spectroscopy shows that the 5, 18-dibenzyl derivative () of () forms a 1:1 inclusion compound with ethanol in the solid state and undergoes ring inversion ( ? *) between enantiomeric propeller-like conformations in solution against a barrier of 21.1 kcal mol?1相似文献
Phosphorus pentafluoride was reported long ago to give adducts 2 PF5 ·5 NH3 (1) and nNH3·PF5 (n= 1 ? 4) (2). None of the compounds was characterised in detail. Repeating the reaction of PF5 and NH3 we found the adduct H3N·PF5, , in 8% yield besides (H2N) 2PF3 (3) and NH4PF6. However, HF and (F2P=N)3 gave in 41% yield. The 1H, 19F, and 31P n.m.r. spectra of exhibit 14NH, 14NPF(cis), and 14NP coupling. The x-ray structure determination shows almost perfect octahedral geometry at phosphorus with a PN bond length of 1.842 ā. Compound is soluble in water without decomposition. Treatment with NH3 leads to the anion H2NPF5?. Upon heating forms in good yield H2NPF4 and NH4PF6. Without a solvent and NH3 react to give (H2N) 2PF3. A mechanism for the ammonolysis of PF5 is proposed. 相似文献
Previous (1) work on ternary chalcopyrite solid solution formation has shown that the difference in end point axial ratios () is an important factor in determining the extent of mutual solubility. It was concluded that when complete solid solubility will not occur. In this work it is shown that complete solid solution formation in the systems AgAlS2AgInS2 (), AgGaS2AgInS2 () and AgAlSe2AgInSe2 () does occur. This shows that the value of as an upper limit for solid solution formation can be approached closely. 相似文献
Reaction of the amines (CF3)2NX (X=Cl,Br) with norbornadiene either in solvent (CH2Cl2) at ?78 °C in the dark or in the vapour phase at 20 °C in daylight gives a mixture of 3-halogeno-5-(-bistrifluoromethylamino)nortricyclene (, -and , -isomers) and -5-(-bistrifluoromethylamino)- -7-halogenonorbornene in quantitative yield formed halonium ion addition to the diene. The reaction of the amine (CF3)2NBr in solvent Me2O or Et2O at ?78 °C in the dark gives the same products in low yield, together with 3-bromo-5-alkoxynortricyclene (, - and , -isomers) and the amine (CF3)2NR (R=Me, Et) in high yield. 相似文献
Optical absorption and emission spectra are reported for single crystals of the cubic elpasolite Cs2NaSmCl6. The variable temperature spectra obtained at high resolution are assigned using energies and relative intensities. Transitions from the ground level, 6H to cystal fi levels of 6H-, 6F-, 4G-, 4F,, 4I, and 6P, are located and characterized. Intensity calculations are reported for magnetic dipole allowed transitions. The dominance of vibronic intensity in 6H→6F - and 6P, transitions is accounted for qualitatively through the ligand polarization model involving quadrupole metal (Sm3+)-ligand (Cl?) interaction mechanisms. The Eu″(6H)→E′(6H) Eu′(6F) no-phonon transition is postulated to be pure electric quadrupole allowed. The ground state magnetic moment is determined to be very small from magnetic circular dichroism (MCD) spectra.This study has led to the assignment of nearly all of the crystal field levels in the visible and IR region for Cs2NaSmCl6. A total of 27 such levels were identified, 17 from no-phonon transitions and the rest from vibronic transitions. The magnetic dipole intensity calculated using intermediate coupling Oh wavefunctions along with a crystal field analysis of the splitting pattern was used in the assignment of the levels. Vibronic bands were observed for all transitions and their vibrational symmetries were tentatively assigned. MCD data were used to determine the magnet moment of the ground state. 相似文献
Simarinolide and Guanepolide are new quassinoids with a C25 basic skeleton isolated from a member of the French Guyanan Simaroubaceae, Simaba cf orinocensis H.B.K. The structure was established by spectral means and that of by X-ray diffraction analysis. The previously known simarolide was also isolated. 相似文献
Pure nuclear quadrupole resonance of 127I in H5IO6 has been reported to occur at 44.976 MHz (m = ±?m = ± transition) and 83.960 MHz (m = ±? m = ± transition) at 296 K (ref. 1). Using an externally quenched frequency modulated super regenerative spectrometer Zeeman studies have been performed at 296 K on single crystals of H5IO6 growm from aqueous solution by observation of the ±?± transition. The zero-splitting locus method has been employed for the determination of the EFG parameters. The data show that there are two physically inequivalent sites, having average asymmetry parameters, η, of 0.25, located in the unit cell. The maximum field gradient is found to lie along the short bond I-O(2) as suggested by Rama Rao and Weiss (ref. 1). The EFG parameters obtained by detailed molecular orbital calculations (CNDO/2 and INDO method) are compared with the experimental results. 相似文献
A tritriacontanucleotide which has the sequence of the 5half molecule of E.coli glycine tRNA2, was synthesized by the phosphotriester method involving p-anisidate protection for the 3phosphate ends. Di- and trinucleotide units were prepared from 5dimethoxytrityl-2O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 35unprotected nucleosides followed by phosphorylation to give 3phosphodiester blocks. The 3terminal dimers and trimers were synthesized by using 3(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5deblocking of larger fragments. Finally a 3phosphodiester block with a chain length of 20 was condensed with a 5OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2. 相似文献
The reactions of the sulphite radical anion, SO3? (generated from the Ti3+-H2O2-Na2SO3 system at pH 9), in aqueous solutions with some nitroalkane compounds were investigated by using a rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 ms. The SO3? radical added to the double bond of CN in the nitroalkane aci-anions which are the main form of nitroalkanes in aqueous alkaline solutions. From the observed hyperfine splitting constants of the SO3? adducts of nitroalkane aci-anions, the preferred conformation of the adducts was deduced. 相似文献
Adenosine cyclic 3′,5′-phosphoramidate was synthesized by reacting adenosine cyclic 3′,5′-phosphate with POCl3, in trimethyl phosphate for 1 h at O°C, followed by in situ treatment of the reaction mixture with a suspension of (NH4)2CO3 in anhydrous DMF or pyridine or DMF/pyridine mixture for 30 min at 25° C. Diastereoisomers (P)- and (P)- the relative quantities of which depended on the solvent of (NH4)2CO3 treatment, were separated by reversed phase partition chromatography. Hydrolysis of (RP)- and (SP)- proceeded with predominant (90% in 0.1 N HCl, 100% in 0.1 N NaOH) -P-O-C bond breaking. 相似文献
The title compound is the final product of the reaction between dimethylacetylene dicarboxylate and [(η5-C5H5)W(SMe) (CO)3 ]. Its molecular structure has been established by an -ray analysis based on 3301 diffractometric intensities. The crystals are monoclinic, space group 21/, with four molecules in a cell of dimensions = 10.323(2), = 16.016(2), = 10.437(2)», β = 103.56(2)°. After least-squares refinement = 0.036. The tungsten co-ordination is square-pyramidal, the apical site being occupied by the centroid of the cyclopentadienyl ring. The basal co-ordination sites contain two carbonyl groups and also the sulphur and σ-bonded carbon atoms of a chelating carbothiolic methyl ester ligand derived from the incoming alkyne and CO and SMe groups of the original complex. The W-S and σ-W-C bond lengths are 2.440(2) and 2.194(7)». 相似文献
In CFCl3, aziridines react with F2(6 %/N2, 20°C), COF2 (20 %/N2, 40°C) and CF3OF [1] (20 %/N2, 40°C).Substitution products are obtained : l-(aziridine)carbonyl fluorides and l-Fluoroaziridines In (Et)2O, aziridines react with COF2 (20 %/N2, 10°C) and we have the carbonyl fluorides . Products IV can be thermally decomposed into β fluoro isocyanates.In CFCl3, N substituted aziridines react with F2(6%/N2, 20°C) and with CF3OF [2] (20%/N2, 40°C). No reaction is observed with COF2in our conditions (5% to 25%/N2, 80°C to + 40°C).Addition products are obtained : N Fluoro amines β fluorinated , N Fluoro and NN difluoro amines β trifluoro methoxylated and .with R = SO2Ø, COØNO2, Cl. 相似文献
Reaction of the 16 electron monomer [Co(η5-C5H5)(S2C2{CN}2)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η5-C5H5)(S2C2{CN}2)L] which for L = P(OR)3 have J(C55) ca. 6 Hz but J(C55) = 0 for L = PR3. 相似文献
Fe2P4O12 has been prepared and identified as an isotype of the other MII2P4O12 tetrametaphosphates (MII = Ni, Mg, Cu, Co, Mn, Cd). Its monoclinic unit cell: contains 4 formula units. The space group is . For tetrametaphosphates with MII = Ni, Mg, Cu, Co, and Mn we found a new denser phase induced at 80 kbar and 1000°C. In the case of Fe2P4O12 the unit cell of this new form is with Z = 2 and two possible space groups Cc or . This dense phase exists at ordinary pressure for the zinc salt. 相似文献
Four novel polyoxygenated C28-sterols have been identified from the soft coral (the Gulf of Eilat, the Red Sea): the 22,28-lactol of 24-methylcholest-5-en-3β,22(R),25-triol-28-al (), 24-methylcholest-5-en-3β,22(R),25,28-tetraol() and the corresponding 5,6β-epoxides ( and ). 相似文献
A very unusual dithiokikeptopiperazine structure () has been assigned to aspiroclorine, C9H12N2O5S2Cl, produced as a biologically active substance together with canadensolide by , which has been found to be identical with the antibiotic A 30641 from . 相似文献
The synthesis of the 2,6-dideoxy sugars -digitoxose (14), 2-deoxy--fucose (15) and -mycarose (16) from the C4 and C5 chiral synthons (1), (2) and (3), through the intermediacy of the C7 adducts (4), (8) and (12), obtained by addition of diallylzinc onto (1), (2) and (3), is reported. 相似文献
Reaction of [PdCl2(PBut2Ph)]2 with silver acetate gives the internally metalated complex [PButPh]2(μ-Cl)2. This reacts with TlC5H5 and LiC5Me5 with chloride-bridge cleavage to yield C5R5PPButPh (R = H, Me). The complex [PBut2]2(μ-Cl)2,prepared from [PdCl2(PBut3)]2 and CH3COOAg, is analogously converted into C5R5But2. The chloride complex C5H5Pd(PBut5Ph)CI does not eliminate HCl to form C5H5PButPh. 相似文献