The structure of carbon trioxide

Open ( 1 ) and cyclic ( 2 ) singlet forms of CO₃ were investigated by means of ab initio calculations. At the highest level of theory employed, MP 2/6-31G* (which includes the effects of electron correlation), 2 was indicated to be much more stable than 1 and thermodynamically stable toward dissociation into CO₂ and O(³P). The open form 1 has a long O? O bond and can be regarded as a weak dative complex between CO₂ and a singlet oxygen atom.     

Possible high-pressure structures of sulfur trioxide

Calculations with the linearized augmented plane wave method indicate that several high-density forms of sulfur trioxide should be accessible at pressures above 29 GPa, with densities up to 1.7 times larger than the presently known forms of solid SO3.     

Reaction of perfluoropropenylbenzene with sulfur trioxide

Depending on the ratio of the reagents and the reaction conditions, the reaction of perfluoropropenylbenzene with SO₃ in the presence of BF₃ or SbF₅ gives perfluoro--phenylallyl fluorosulfate or perfluorocinnamoyl fluorosulfate; hydrolysis of the latter gives perfluorocinnamic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2073–2076, September, 1989.     

Reaction of octafluoronaphthalene with sulfur trioxide

Conclusions An addition product is formed by reaction of sulfur trioxide with octafluoronaphthalene, which indicates in favor of the intermediate formation of a polyfluorinated -complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 705–707, March, 1970.     

Effect of the medium on the decomposition rate of di-t-butyl trioxide

Using the chemiluminescence method, the effect of the medium on the overall rate constant of the thermal decomposition of di-tert-butyl trioxide has been studied. In all solvents investigated the decomposition occurs in accordance with a first order rate law. The effect of solvent on the rate constant (0°C) is analyzed.     

A theoretical study of the force field for carbon trioxide

Geometries force constants and harmonic frequencies are calculated for the cyclic (dioxirane) structure of CO₃ by ab initio SCF methods using the 3-21G, 3-21G(*). 6-31G and 6-31G* bases calculated frequency shifts for isotopomeric species agree with experiment and lend support to the vibrational assignments of Jacox and Milligan. Earlier arguments for and against the cyclic, cyclic and open structures of CO₃, based upon the “physical reasonableness” of valence force constants are shown to be invalid owing to the dependence of conventional “rigid” force constants upon the choice of valence coordinates. The use of “relaxed” force constants as a basis for meaningful comparison of force fields for molecules described by different sets of redundant valence coordinates is demonstrated.     

Neutron powder profile studies of the gamma uranium trioxide phases

Neutron powder profile studies show the existence of three phases in gamma uranium trioxide between 373°K and 77°K. The three phases are closely related and the transitions smooth and displacive. At 373°K, γ-UO₃ is tetragonal, with a = 6.9013 (5) and c = 19.9754 (18) Å, and space group $\text{I4}{}_1\text{amd(}\text{D}{}^{19}{}_{\mathrm{4h}}\text{)}$. At 323°K, γ-UO₃ becomes orthorhombic, space group F_ddd(D²⁴_2h), with the cell dimensions (293°K) a = 9.787 (3), b = 19.932 (4) and c = 9.705 (3) Å. There is a further transition between 293°K and 77°K, and, at 77°K, the orthorhombic dimensions of the pseudocell are a = 9.8225 (7), b = 19.8487 (15), and c = 9.6318 (7) Å. The neutron diffraction studies show that, in all three phases, the coordination polyhedra of the two crystallographically distinct uranium atoms are octahedral and (dodecahedral-2) respectively. At 293°K, the shortest UO distance is 1.796 (6) Å, and thus there are no pure uranyl bonds, in agreement with the infrared spectrum. The UO distances are precise to about ± 0.006 Å, about ten times the precision of an earlier X-ray single-crystal study, in which the conclusions were in conflict with the infrared spectrum. The structure is made up of parallel chains of edge-fused U(2) octahedra, cross-linked by U(1) dodecahedra. The atomic shifts are not great in going from 373°K to 77°K; at 293°K the data will refine in the pseudotetragonal cell as well as the true orthorhombic cell, and the 77°K data will refine in the F_ddd cell.     

Electrochemical crystal growth in the cesium molybdate-molybdenum trioxide system

A systematic investigation of crystal growth in the cesium molybdate/molybdenum trioxide system is described. A previously unknown blue cesium molybdenum bronze phase has been prepared as well as the known red bronze, Cs_0.33MoO₃, and high-quality crystals of the Magneli-phase compound, γ-Mo₄O₁₁. This new blue bronze, with empirical formula, Cs_0.19MoO_2.85, is monoclinic with cell constants, a = 19.198(4) Å, b = 5.519(2) Å, c = 12.213(2) Å, and β = 119.44(2)°. Measurements of the susceptibility and of the resistivity vs temperature are reported. As is the case for other alkali molybdenum bronzes, the product formed is determined by the molar ratio of alkali molybdate to molybdenum trioxide and the melt temperature.     

氧化铬柱层状三氧化钼的合成

采用醋酸铬[Cr(OAc)~3]水溶液与具有层状结构的钼青铜{[Na(H~2O)~5]~0~.~2~5MoO~3]进行离子交换瓜制得铬齐聚体柱撑的层状氧化钼化合物。经350℃焙烧后,首次得到了多孔高比表面积的氧化铬柱层状氧化钼材料。通过XRD,TEM,DTA和BET测试手段对其进行了表征,并考察了350℃时不同的焙烧气氛对产物层间距和表面积等的影响。结果表明,在不同气氛中焙烧,产物层间距相同(1.092nm),但比表面积有很大的变化,其中,在含4%(体积分数)氧气的氮氧混合气中焙烧,获得的样品比表面积(BET)最大,达82.4m^2·g^-^1,平均孔径为6.42nm。     

Reaction of internal fluoroolefins with sulfur trioxide

Conclusions In the presence of SbF₅ sulfur trioxide undergoes insertion reactions into the allylic C-F bonds of perfluoro-2-alkenes to give perfluoroalk-2-enyl fluorosulfates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1864–1868, August, 1985.     

三氧化钼溶胶凝胶光致变色的研究

通过金属钼粉与过氧化氢溶液反应制备三氧化钼溶胶和凝胶,在高压汞灯的照射下,溶胶和凝胶由浅黄色变成蓝色。Raman光谱研究表明：通过紫外光照,MoO3凝胶结构进行了重整,呈有序排布。乙醇相的MoO3溶胶在紫外光照或长期自然光照下,均表现出光致变色特性。电子自旋共振(ESR)和X射线电子能谱(XPS)研究表明：空气中的MoO3经光照同时接受质子和电子后,生成了蓝色的钼青铜,其中Mo^6^+被还原成了Mo^5^+离子。     

Silver niobium trioxide,AgNbO3

The present structure determination of silver niobium trioxide at 291 K was performed on a twinned single crystal with a predominant presence [about 93 (1)%] of one twin domain. The sample contained traces of V (about 1 atomic %). This study confirms that the room‐temperature phase of AgNbO₃ is isostructural with the room‐temperature phase of NaNbO₃, i.e. it is a tilted perovskite. Structural deviation in AgNbO₃ from centrosymmetry was not detected in this study and its structure was refined in Pbcm, though a previous study indicated ferroelectricity below 350 K, in contrast with NaNbO₃.