Formation and phase transition of cobalt molybdate in cobalt oxide-molybdenum trioxide-alumina system

In the cobalt oxide-molybdenum trioxide-alumina system with a molar ratio of 1:1:1, the amounts of the high-temperature modification (a) of CoMoO₄ formed during heating from 500 to 800°C and the low-temperature modification (b) formed by phase transition during the subsequent cooling to room temperature are influenced by the kinds of alumina used, such as α-, γ- and calcined γ-aluminas. Powder X-ray diffraction analysis revealed that in an α-alumina system formation of a-CoMoO₄ is most favorable at a calcination temperature of 500°C and phase transition from a- to b-CoMoO₄ during cooling is enhanced by higher calcination temperatures. In the γ-alumina system, formation of a-CoMoO₄ is slight at 500°C but increases with increase in the calcination temperature, as does slightly the degree of phase transition from a- to b-CoMoO₄ upon cooling. In a system containing calcined γ-alumina, formation of a-CoMoO₄ similar to α- and γ-alumina systems was observed to occur at 500°C and 800°C, respectively, together with phase transition to b-CoMoO₄ during cooling. The degree of dispersion in the CoOMoO₃ coexistent system is affected by the particle size of aluminas, such as coarse α-, fine amorphous γ- and calcined γ-alumina consisting of both sizes, as observed with electron microscopy. Presence of finer γ-alumina is considered to suppress or retard the solid state reaction and phase transition.     

Disordered modifications of cobalt molybdate

The structures of recently discovered new high-temperature modifications of cobalt molybdate, a′-and a″-CoMoO₄, were determined. a′-and a″-CoMoO₄ appear after the phase a-CoMoO₄ is heated above the temperature range 700–1000°C. They seem to be the disordered modifications of a-CoMoO₄ with metal atoms distributed at random in an a-CoMoO₄ oxygen network.The F(hkl) values, calculated for variously disordered a-CoMoO₄ structure, were compared with the observed intensities of diffraction lines changing in the course of a → a′ and a → a″ transitions. It was concluded that a″-CoMoO₄₄ has a completely disordered structure with random distribution of both Co and Mo atoms in oxygen interatomic voids. The a′-CoMoO₄ is a partly disordered modification, with random distribution of some cations only.The temperature and the kind of order-disorder transition depend on the method of preparation of a-CoMoO₄ samples.The disordered modifications of cobalt molybdate may be supercooled—even to room temperature—before it transforms rapidly into low-temperature b-CoMoO₄ form.     

Temperature dependence of broadening and shifts of methane lines in the ν4 band

We have recorded high-resolution absorption spectra of methane broadened by dry air and by N₂ at temperatures from −63 to 41°C using a Fourier transform spectrometer. These spectra have been analyzed to determine pressure broadening and line-shift coefficients, along with their temperature dependences, for 148 lines in the ν₄ fundamental band of ¹²CH₄. The experimental uncertainties for lines with J″≤10 are generally <2% for the broadening coefficient b⁰_L, 6–12% for its temperature dependence exponent n, 6–20% for the line-shift coefficient δ⁰, and 20–40% for its temperature dependence coefficient δ′; for J″> 10 the experimental uncertainties are somewhat larger. These results, especially for N₂-broadening, are in excellent agreement with other recent measurements. Since the present results cover a wide range of rotational quantum numbers (J″ up to 14), the variation of the temperature dependence of the half-widths and shifts from line to line within the ν₄ band is also examined.     

Etude des petits cycles—XXXVI. Photo-oxygenation d'alkylidenecyclopropanes. Syntheses specifiques d'alkenylcyclopropanols,de β′-hydroxy α-enones et d'α,α′-dienones

The dye-sensitized photo-oxygenation of alkylidenecyclopropanes 1a–4a at –50°C gives the hydroperoxydes 1b–4b, which were reduced in situ by PPh₃ into 1-alkenylcyclopropanols 1c–4c in high yield. At higher temperatures, 1b–4b rearranged exclusively into β′-hydroxy α-enones 1d–4d if pyridine was added (α,α′-dienones 1e–4e are also formed competitively in absence of pyridine). At 3°C the photosensitised oxygenation of alkylidenecyclopropanes 1a–4a gives ketones 1k–4k, cyclobutanones 1i–4i and β′-hydroxy α-enones 1d–4d. The origin of products is discussed.     

Phase equilibria in the Ag4SSe–As2Se3 system

The phase diagram of the system Ag₄SSe–As₂Se₃ is studied by means of X-ray diffraction, differential thermal analyses and measurements of the microhardness and the density of the materials. The unit-cell parameters of the intermediate phases 3Ag₄SSe·As₂Se₃ (phase A) and Ag₄SSe·2As₂Se₃ (phase B) are determined as follows for phase A: a=4.495 Å, b=3.990 Å, c=4.042 Å, α=89.05°, β=108.98°, γ=92.93°; for phase B: a=4.463 Å, b=4.136 Å, c=3.752 Å, α=118.60°, β=104.46°, γ=83.14°. The phase 3Ag₄SSe·As₂Se₃ and Ag₄SSe·2As₂Se₃ have a polymorphic transition α?β consequently at 105 and 120°C. The phase A melts incongruently at 390°C and phase B congruently at the same temperature.     

Measurement of the relaxation transitions of nitrocellulose based gunpowder

The formation of a new sulfate compound K₄H₂(SO₄)₃ is obtained by evaporation at 25°C of an aqueous solution, which was formed by a mixture of K₂SO₄ and H₂SO₄. The characterization of this solid is carried out by X-ray diffraction, thermal and infrared analyzes. The heat treatment was carried out in interval 25–700°C; the end product of the thermal evolution is K₂SO₄. The vibration bands relating to SO₄ and OH groups were highlighted by the infrared spectroscopy.Moreover, one study of ionic conductivity on this solid compound was carried out according to the temperature in interval 25–80°C. Its activation energy is 0.47 eV. The X-ray intensities collection obtained on a monocrystal of K₄H₂(SO₄)₃ gives the following cell parameters: a=7.035(5), b=19.751(4), c=23.466(2) Å, β=95.25(1)°.     

The temperature dependence of the viscoelastic softening and terminal dispersions of linear amorphous polymers

Thermorheological simplicity is shown to hold for poly(vinyl acetate) in the temperature range extending from T_g + 25°C to T_g + 80°C. Between T_g and T_g + 25°C the softening (glass to rubberlike) viscoelastic dispersion exhibits time-scale shift factors a_T different from those of the terminal (rubberlike to steady-state) dispersion. The a_T values calculated from zero-shear viscosities coincide with those from the terminal dispersion in the temperature range 60–154°C (T_g ? 35°C). The a_T shifts obtained from the response in the terminal dispersion can be fitted to the Williams, Landel, and Ferry equation over the entire temperature range 42–154°C. The a_T obtained from the softening dispersion is shown to exhibit a different functionality. An empirical modification of the Doolittle equation yields a very flexible relation which can be fitted to some a_Ts which cannot be represented by the usual Doolittle free-volume expression.     

An independent investigation of the crystal structure of 1,8-dinitronaphthalene (orthorhombic form) at 22 and 97°C

The crystal and molecular structure of the orthorhombic form of 1,8-dinitronaphthalene, C₁₀H₆N₂O₄, has been reinvestigated at 22°C and examined at 97°C using single-crystal diffractometer data in order to throw some light on the structural aspects of the polymorphism of the title compound. The space group of the crystal is P2₁2₁2₁ with a = 11.375 (1), b = 14.974 (5), c = 5.388 (1) Å at 22°C and a = 11.475 (1), b = 15.002 (1), c = 5.425 (6) Å at 97°C. Z = 4 at both temperatures. The data, collected with CuK_α radiation, were refined by full-matrix least squares to R = 0.049 for 1087 reflexions (22°C) and R = 0.061 for 1078 reflexions (97°C). The structure was found to be in agreement with that determined by Z. A. Akopian, A. I. Kitaigorodskii, T. J. Struchkov (Zh. Strukt. Khim.6, 729 (1965)). Changes occurring on heating to a temperature of 97°C, which is close to the transition temperature (of c → pc type) 100–105°C, suggest that the possible mechanism of the phase transition is that of the displacive transformation of secondary coordination. Anistotropic temperature factors of the majority of atoms increased by ca. 50% with no particular direction of atom vibrations being distinguished.     

Untersuchungen an Tetranatrium-cyclo-tetraphosphat(V) und seinen Hydraten

A reinvestigation of the system (NaPo₃)₄/H₂O has been carried out. Besides the already known tetra-hydrate and anhydrous form, a mono-hydrate in the temperature range 100–120°C exists. Single crystals were obtained by crystallization from aqueous solutions containing higher alcohols (e.g. ethyleneglycol) at ～115°C. The crystal structure was solved by X-ray methods (orthorhombic;P2₁2₁2₁;a=1365.4(2),b=1 347.5(3),c=629.1(3)pm;Z=4; 2774 diffractometer data;R=0.053). The cyclic anions exhibit point symmetryD _2d with all terminal oxygens in eclipsed conformation. With respect to the (NaPO₃)₄-part of structure, mono-hydrate and anhydrous forms are isostructural; lattice parameters of the latter area=1 380.8(2),b=1 363.3(2),c=602.7(2) pm. The transition mono-hydrate to anhydrous form occurs topochemically and is reversible.     

Bis(benzoato)-bis(π-cyclopentadienyl)-titan(IV): Darstellung in wässriger lösung und struktur einer neuen modifikation

The reaction of titanocene dichloride with sodium benzoate in aqueous solution gives titanocene dibenzoate in high yield. Crystals of a modification different from the one described recently by Hoffman et al. can be obtained by recrystallization from chloroform: orthorhombic, space group P2₁2₁2₁, Z = 4 and lattice constants at − 120°C a 21.154(4), b 12.529(4), c 7.574(2) Å. Whereas the TiO bond for one of the benzoate groups is a normal σ-bond, the other one seems to have a considerable additional π-bond character.     

Lateral thermal expansion of cellulose Iβ and IIII polymorphs

Measurements of the thermal expansion coefficients (TECs) of cellulose crystals in the lateral direction are reported. Oriented films of highly crystalline cellulose I_β and III_I were prepared and then investigated with X‐ray diffraction at specific temperatures from room temperature to 250 °C during the heating process. Cellulose I_β underwent a transition into the high‐temperature phase with the temperature increasing above 220–230 °C; cellulose III_I was transformed into cellulose I_β when the sample was heated above 200 °C. Therefore, the TECs of I_β and III_I below 200 °C were measured. For cellulose I_β, the TEC of the a axis increased linearly from room temperature at α_a = 4.3 × 10^?5 °C^?1 to 200 °C at α_a = 17.0 × 10^?5 °C^?1, but the TEC of the b axis was constant at α_b = 0.5 × 10^?5 °C^?1. Like cellulose I_β, cellulose III_I also showed an anisotropic thermal expansion in the lateral direction. The TECs of the a and b axes were α_a = 7.6 × 10^?5 °C^?1 and α_b = 0.8 × 10^?5 °C^?1. The anisotropic thermal expansion behaviors in the lateral direction for I_β and III_I were closely related to the intermolecular hydrogen‐bonding systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1095–1102, 2002     

Carbon-nitrogen bond formation in the reaction of the reaction of diphenyl diazomethane Ph2 CN2 with diiron-carbene complexes (Fe2(CO)7x03BD;-C(R)C(NEt2)x03BD;-C(R)C(NEtx03BC;-C(R)C(NEt2)N(NCPh2)x03BC;-C(R)C(NEtx03BC;-C(R)C(NEt2)NN(CPh2)x03BC;-C(R)C(NEt)]

The diiron ynamine complex [Fe₂(CO)₇{μ-CR)C(NEt₂)}] (1:R=Me,2:R = C₃H₅.3:R=SiMe₃.4:R = Ph) reacts at room temperature with diphenyldiazomethane Ph₂CN₂, in hexane to yield complexes [Fe₂(CO)₆{C(R)C(NEt₂)N (NCPh₂)] (5a:R=Me,6a:R=C₃H₅.7a R=SiMe₃.8a:R=Ph) resulting from the insertion of the terminal nitrogen atom into the Fe=C carbene bond. Insertion the second nitrogen atom and formation of compounds [Fe₂(CO)₆zμ-C(R)C(NEt₂)NN(CPh₂)}] (5b:R=Me,6b:R=C₃H₅,7b:R=SiMe₃,8b:R=Ph) is observed when compounds5a-5a are treated in refluxing hexane. Transformation of compoundsa tob is also obtained at room temperature within a few days. All compounds were identified by their¹H NMR spectra. Compounds6a, 7a, 8a, and8b were characterized by single crystal X-ray diffraction analyses. Crystal data: for6a: space group = P2₁/n,a=12.853(1) A,b=24.800(7) A,c=8.947(6) A,β=99.29(3)°,Z=4, 2227 rellectionsR=0,038; for7a: space group=Pl,a=ll.483(4) A,b=14.975(4) A,c = 17.890(8) A,α = 82.80(3)°,β=94.29(7)°,γ=85.42(2),Z = 4, 5888 reflectionR = 0.035: for8a: space group = Pcab.a = 31.023(8) A.b=20.137(1) A.c=9.686(2) A.Z=8. 1651 reflections,R=0.071; for8b: space group=P2₁/n,a=21.459(4),b=10,100(3) A,c=28,439(8) A,ß=103.86(4)°,Z=8. 2431 reflections.R=0.057.     

Chelating diamide complexes of titanium: new catalyst precursors for the highly active and living polymerization of α-olefins

The reaction of RHN(CH₂)₃NHR (1a,b) (a, R=2,6-ⁱPr₂C₆H₃; b, R=2,6-Me₂C₆H₃) with 2 equiv of BuLi followed by 2 equiv of ClSiMe₃ yields the silylated diamines R(Me₃Si)N(CH₂)₃N(SiMe₃)R (3a,b). The reaction of 3a,b with TiCl₄ yields the dichloride complexes [RN(CH₂)₃NR]TiCl₂ (4a,b) and two equiv of ClSiMe₃. An X-ray study of 4a (P2₁/n, a=9.771(1) Å, b=14.189(1) Å, c=21.081(2) Å, β=96.27(1)°, V=2905.2(5) ų, Z=4, T=25°C, R=0.0701, R_w=0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN₂-plane. Compounds 4a,b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH₂)₃NR]TiMe₂ (5a,b). An X-ray study of 5b (P2₁2₁2₁, a=8.0955(10) Å, b=15.288(4) Å, c=16.909(3) Å, V=2092.8(7) ų, Z=4, T=23°C, R=0.0759, R_w=0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium–methyl bond lengths of 2.100(9) Å and 2.077(9) Å. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst·h were obtained in neat 1-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C₆F₅)₃ catalyze the living aspecific polymerization 1-hexene. Polydispersities (M_w/M_n) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph₃C}⁺[B(C₆F₅)₄]⁻. A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine.     

Crystal structure and magnetic structure of TbOOH

The monoclinic modification of terbium oxide hydroxide, TbOOH, was prepared using hydrothermal technique. The crystal structure was investigated by three-dimensional single-crystal X-ray analysis and was refined to a conventional R-value of 8.1%. The space group is $\text{P2}{}_1\text{m}$, No. 11, with a = 6.04 Å, b = 3.69 Å, c = 4.33 Å, and β = 109.0°. The terbium atom is seven coordinated with oxygen atoms, and the structure is not hydrogen bonded.The compound is antiferromagnetic with a Néel temperature of 10°K. Neutron diffraction powder patterns were measured at 300°K and 4.2°K. The magnetic super lattice reflections were indexed on the basis of a monoclinic unit cell with the dimensions a_M = 2a, b_M = b, c_M = c, and β_M = β, where a, b, c, and β are the dimensions of the chemical unit cell. The structure contains two independent magnetic atoms. A nonclinear antiferromagnetic arrangement of the spins describes the magnetic structure. The spin at one atom has an angle of 43° with the ac plane and the projection of the spin on the ac plane has an angle of 59° with the a axis. The spin on the other atom has an angle of ?43° with the ac plane, the projection having the same angle of 59° with the a axis.     

Nombre de transport et conductivité cationique dans l'oxyde de nickel: NiO

Ionic transport number measurements have been made on single crystals of NiO over the temperature range 900–1300°C and for oxygen partial pressures varying from 10^?8 to 1 atm. At 1000°C and in air, t_Ni ～ 2 × 10^?7. The variation in cationic conductivity as a function of oxygen partial pressure suggests that V′_Ni is the dominant defect at high temperature and low oxygen pressure and that V″_Ni is the dominant defect at low temperature and high oxygen pressure.     

Efficient syntheses of novel indeno[1,2-b]chromenone derivatives via hetero-Diels-Alder reactions of 2-(arylmethylene)-1H-indene-1,3(2H)-diones with enaminones

Efficient syntheses of novel 10-aryl-5a-(arylamino)-9-hydroxy-5a,6,7,8-tetrahydroindeno[1,2-b]chromen-11(10H)-one derivatives has been reported by [4+2] cycloaddition reactions of electron-deficient 2-(arylmethylene)-1H-indene-1,3(2H)-dione heterodienes with electron-rich enaminones in [bmim]BF₄ at 80?°C and in acetic acid at 80?°C. Dimedone/cyclohexane-1,3-dione enaminones have been used as dienophiles in Inverse Electron Demand hetero-Diels-Alder reactions. The products were obtained in high yields by a simple work up.     

Kristall-und molekülstrukturen zweier modifikationen de hexaphenyldigermylsulfids (C6H5)3GeSGe(C6H5)3

en Two differnt crystal modifications of hexaphenyldigermanium sulfide (C₆H₅GeSGe(C₆H₅)₃ (I and II were obtained by crystallization from hot benzene/methanol or form ethanol at 20°C. Single crystal X-ray structural analyses for both I (low temperature data at ?130°C) and II (at 20°C) (I, R = 0.046; II, R = 0.048) were performed. I is monoclinic, P2¹/c, with a = 11.020(3), b = 15.473(3), c 18.606(3) »,π = 106.92(2)°, Z = 4; II is orthorhombic, P2₁2₁2₁, with a = 2.617(2), b = 17.345(3), c = 18.408(3) », Z = 4.The molecules have different conformeric structures with respect to a rotation of the (C₆H₆)₃Ge groups around the Ge bonds with very similar bond lenghts and angles. Bond data for I(II) are: GeS 2.212(1) and 2.261(1) » (2.227(2) and 2.240(2) »); GeC 1.933(4) ? 1.971(4), mean 1.945(5) » (1.931(7)?1.954(7), mean 1.943(4) »); GeSGe 111.2(1)° (110.7(1)°). The Ge bond lenghts are comparable to those in thiogermanates and do not indicate significant π-bond contributions.     

Etude cristallochimique de derives du chrome(0) : I. Structure cristalline et moleculaire du benzoate de methyle chrome dicarbonyle thiocarbonyle

The crystal and molecular structure of methylbenzoatechromium dicarbonyl thiocarbonyl has been determined by a single-crystal X-ray study. The compound crystallizes with two molecules in a unit cell of symmetry P$\text{1}$, with the following parameters: triclinic system, a = 7.108(3), b = 10.340(4), c = 8.523(3) Å; α = 89.75(6), β = 95.89(4), γ = 105.50(4)°; V = 601 ų; d_m = 1.57 ± 0.05, d_c = 1.56. The structure has been refined to R and R″ values of 0.030 and 0.038 respectively, for 1963 independent reflections. The main feature of the molecule is the C_s symmetry of the Cr(CO)₂CS group with a CrC(S) bond length of 1.792(2) Å, shorter than the CrC(O) bond length, mean: 1.849(3) Å.     

Etude thermoanalytique de substances psychotropes. IV. Lorazepam et oxazepam

We have studied the thermal behaviour of lorazepam (a) and oxazepam (b), defined the crystal form and the thermal stability. After recrystallization in several solvents under known temperature and pressure conditions the thermoanalytical study of samples has shown polymorphs for (a) and (b) and pseudopolymorphs for (a), (a) Polymorphs are I (t_f = 183°C), II (T_f =173°C), III (T_f =170°C). IV (_Tf, =163°C), V (_Tf =158°C), VI (_Tf, =153°C), and seven pseudopolymorphs, three of which are clathrate type of 1:1 molar composition with propanol, chloroform and isopentanol. We have found eight polymorphs for (b): I (T_f = 207°C), II (T_f=201°C), III (T_f=193°C), IV (T_f=189°C). A, B, C and D show a solid ? solid transition. Commercial samples of (a) are form I, those of (b) are form II.A spectral and dissolution kinetic study completes the thermoanalytical results in relation to biological availability.     

Beiträge zum thermischen Verhalten von Sulfaten. II. Zur thermischen Dehydratisierung des ZnSO4 · 7 H2O und zum Hochtemperaturverhalten von wasserfreiem ZnSO4

Contributions to the Thermal Behaviour of Sulfates. II. On the Thermal Dehydration of ZnSO₄ · 7 H₂O and the Effect of High Temperature upon Anhydrous ZnSO₄ The dehydration of ZnSO₄ · 7 H₂O and effect of high temperature upon unhydrous ZnSO₄ was examined by means of continous high temperature Guinier photographs. On heating in air ZnSO₄ · 7 H₂O decomposes stepwise to ZnSO₄ · 6 H₂O, to an unknown hydrate, to the monohydrate and finally to N? ZnSO₄, which is the thermodynamically stable modification at S.T.P. At about 700°C a reversible transformation to H-ZnSO₄ can be observed which can start from N? ZnSO₄ or H-ZnSO₄, proceeds to the oxide sulfate Zn₃O(SO₄)₂ and finally to ZnO. ZnSO₄ · 6 H₂O crystallizes monoclinically in the hexahydrite structure with a_25°C = 9.981 Å, b_25°C = 7.250 Å, c_25°C = 24.280 Å, β_25°C = 98.45°, Z = 8, space group: C 2/c. Cubic H-ZnSO₄ is the first A²⁺B⁶⁺O₄ compound of H-Cristobalit structure; probable space group F 4 3 m with a_700°C = 7.18 Å, Z =4, N-Zn₃O(SO₄)₂ is monoclinic probable space group B 2 with a_25°c=13.987 Å, b_25°c=6.706 Å, c_25°c =7.379 Å β_25°c=90.69°, Z=4, Above 420°C N-Zn₃(SO₄)₂ becomes orthorhombic where at first of all H′-Zn₃O(SO₄)₂ which has a reversible transformation point to H-Zn₃O(SO₄)₂ at 655°C is formed. The probable space group of H-Zn₂O(SO₄)₂ is C 222₁ with a _850°C = 7.36 Å, b_350°C = 13.96 Å, c_850°C = 6.79 Å Z = 4, The solid solution N? Cu_1,5Zn_1,5O(SO₄)₂ is isotypic with N? Zn₃O(SO₄)₂ and has the lattice constants a_25°C = 14.03 Å, b_25°C = 6.62 Å, c_25°C = 7.33 Å, β_25°C = 90.58°, Transoformations into the non quenchable high temperature modifications H-ZnSO₄, H′-Zn₃O(SO₄)₂ and H-Zn₃O(SO₄)₂ are displacive. The thermal expansion of N-ZnSO₄ and H-ZnSO₄ and H-ZnSO₄ has been exa-mined.