Structure analysis of 3β-chloro-6-nitrocholest-5-ene

The crystal structure of the title compound (C₂₇H₄₄NO₂Cl) is determined by X-ray structure analysis. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with the unit cell parameters a = 7.207(1) Å, b = 11.292(1) Å, and c = 32.373(5) Å. The structure is solved by direct methods and refined to R = 0.060. Rings A and C exist in the chair conformation. Ring B adopts a half-chair conformation, and ring D is a 13β envelope. The A/B ring junction is quasi-trans, while the B/C and C/D ring systems are trans fused about the C(8)–C(9) and C(13)–C(14) bonds, respectively. Molecules are linked together by the C-H?O hydrogen bonds.     

Synthesis and structure analysis of 2-(2′-propanonylthio)-3-(o-methyl phenyl) quinazol-4(3H)-one

The three-dimensional molecular and crystal structure of 2-(2'-propanonylthio)3-(o-methyl phenyl)quinazol-4(3H)-one has been determined by X-ray crystallographic methods. This compound crystallizes in the orthorhombic space group P_bca with unit cell parameters: a=9.649(5), b=30.102(10), c=11.403(9)Å. It has been solved by direct methods and refined to a residual index of 0.054. The magnitude of torsion along C16— C11— N3— C4 bond is 93.5(4)°. The dihedral angle between the plane comprising all the ring atoms of quinazoline moiety and the atoms of the methyl substituted phenyl ring is 94.12(1)°. The crystal structure is stabilized by one intramolecular C— HsO interaction and three intermolecular C— HsN contacts.     

Air-stable liquid clathrates. 1. Crystal structure of [NBu4][Br3] and reactivity of the [NBu4][Br3]·5 C6H6 liquid clathrate

[NBu₄][Br₃] interacts with C₆H₆ to form an air-stable liquid clathrate. The tribromide anion reacts with phenol to give para-bromophenol in>95% yield. The HBr which is generated in the reaction combines with the Br^– anion to form [Br-H-Br]^–. The latter forms the basis for a new liquid clathrate, [NBu₄][Br-H-Br]·n C₆H₆. The parent salt, [NBu₄][Br₃], crystallizes in the monoclinic space group C2/c witha=12.983(5),b=10.380(7),c=16.222(6) Å,=93.93(3)°, andD _c =1.47 g cm^–3 forZ=4. The final R value is 0.068 based on 787 observed reflections.     

Thermodynamic analysis of the W-Al2O3 system near the melting temperature of Al2O3. I. Evolution of the system in the pressure range of 1 × 10−1−1 × 10−4 bar

The changes in the main chemical reactions occurring upon the interaction between tungsten and the evaporation products of Al₂O₃ melt are considered at a fixed temperature (2400 K). The concentrations of the components coexisting in equilibrium in a closed system under isobaric-isothermal conditions are determined by stochastic simulation for low (× 10⁻¹−1 × 10⁻³ bar) and high (1 × 10⁻⁴ bar) vacuum. It is shown that the gas-liquid-solid system is in heterogeneous equilibrium for the basic component ratio W: Al₂O₃ = 1: 1 in the entire pressure range under consideration. A detailed study of the chemistry of this system should facilitate the choice of the optimal conditions for growing leucosapphire crystals from melt.     

2α-Hydroxy-3α-[N-alkyl(aryl)]pinanoamines. Part I. Preparation and nature of some Schiff bases of 2α-hydroxypinan-3-one. Crystal and molecular structure of α-hydroxy-2,6,6-trimethylbicyclo[3.1.1]hepta-3-ylidenaminobenzene

Some Schiff bases of 2-hydroxypinan-3-one, being precursors of 2-hydroxy3-[N-alkyl(aryl)]pinanoamines, were obtained. The crystal structure of racemic 2-hydroxy-2,6,6-trimethylbicyclo-[3.1. 1]hept-3-ylidenaminobenzene was determined. The Schiff bases were obtained in two forms: solid form (racemate) and liquid form (optically pure). As it appeared from crystallographic studies of the racemic form, in the solid state there are intramolecular-H-bonded dimers.     

Primary to secondary sphere coordination of 18-crown-6 to lanthanide (III) nitrates: Structural analysis of [Pr(NO3)3-(18-crown-6)] and [M(NO3)3(OH2)3]·18-crown-6 (M=Y,Eu, Tb−Lu)

The direct reaction of hydrated lanthanide nitrate salts with 18-crown-6 in 31 CH₃CNCH₃OH has resulted in the isolation and structural characterization of [Pr(NO₃)₃(18-crown-6)] and [M(NO₃)₃(OH₂)₃]·18-crown-6 (M=Y, Eu, Tb–Lu). (The Eu and Yb analogs were confirmed with preliminary cell data only.) [Pr(NO₃)₃(18-crown-6)] is 12-coordinate icosahedral and crystallizes in the orthorhombic space group Pbca with (at 20°C)a=12.230(2),b=15.598(4),c=21.777(9)Å andD _calc=1.89 g cm^–3 forZ=8. The seven isostructural [Pr(NO₃)₃(18-crown-6)] complexes all contain 9-coordinate capped square antiprismatic metal centers hydrogen bonded via the bound water molecules to D_3d 18-crown-6 within the lattice to form hydrogen bonded polymeric chains. Each complex is orthorhombic Pnma with cell parameters as follows: M=Tb (20°C):a=15.242(6),b=14.253(11),c=11.070(6)Å,D _calc=1.83 g cm^–3 forZ=4; M=Dy (20°C):a=15.248(3),b=14.239(5),c=11.058(3)Å,D _calc=1.84 g cm^–3 forZ=4; M=Y (19°C):a=15.260(2),b=14.238(2),c=11.048(3) Å,D _calc=1.64 g cm^–3 for Z=4; M=Ho (20°C):a=15.226(4),b=14.208(15),c=11.028(3)Å,D _calc=1.86 g cm^–3 forZ=4; M=Er (20°C):a=15.250(3),b=14.208(7),c=11.028(3)Å,D _calc=1.87 g cm^–3 forZ=4; M=Tm (20°C):a=15.246(6),b=14.190(16),c=11.013(6) Å,D _calc=1.88 g cm^–3 forZ=4; M=Lu (21°C):a=15.244(9),b=14.158(6),c=10.980(7)Å,D _calc=1.90 g cm^–3 forZ=4.     

Molecular structures of four triterpenoids. X-ray crystallographic analysis of methyl 2α,3β,23α-triacetoxy-19α-hydroxyurs-12-en-28β-oate

A triterpenoid glycoside has been isolated from the roots of a herb used in traditional Chinese medicine. The molecular structure of this compound and its derivatives have been determined by spectroscopic studies and an X-ray analysis of the 2,3,23-triacetoxy-28-methyl ester of the aglycone. This aglycone belongs to the ursene structure series. The hydroxy group on ring E of these triterpenoids is orientated and the side chains at C(2), C(3), C(4) and C(17) are .,, and orientated, respectively. The C ring, which has a double bond at C(12)=C(13), adopts a sofa conformation.     

Anticancer agent development. 5. X-ray structure and1H nmr spectral analysis of (1α,2α,5α,6α)-2,6-bis(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo[3.3.0]octane-4,8-dione

The title compound, C₂₀H₁₄O₈, Mr=382.3, crystallized from chloroform in the centric space group P¯1 witha=6.516(4),b=6.798(3),c=9.545(7) Å,=85.31(5),=73.87(5), =79.59(4)°,V=399.2 ų, and D_calc=1.59 g cm^–3 forZ=1. Least-squares refinement of 1035 observed [F_o5(F_o)] reflections led to the final agreement index ofR=0.074. The molecule resides on a crystallographic center of inversion and is disordered into two different conformations. This manifests itself as a 50/50 disorder at O(4), C(2), and C(3). The observed structure reveals acis relationship between the bridgehead hydrogen atoms and the aryl rings. The 90 MHz¹H nmr spectrum of the title compound exhibits an AAXX spin system with a H(1)C(2) to H(1)C(3) and H(1)C(2) to H(1)C(3) coupling constant of 2.8 Hz. Computer spectral simulation and Karplus equation analysis are utilized to illustrate a relaxation of the torsion angles between H(1)C(2) and H(1)C(3), and H(1)C(2) and H(1)C(3) is solution.     

2α-Hydroxy-3α-[N-alkyl(aryl)]-pinanoamines. Part II. Synthesis and the nature of some pinanoamines and crystal and molecular structure of 2α-hydroxy-3α-(N-n-butyl)-pinanoamine hydrochloride

Several optically pure representatives of 2-hydroxy-3-[N-alkyl (aryl)] pinanoamines, potential chiral auxiliaries in organic synthesis, were obtained. In addition, a structural examination of 2-hydroxy-3-(N-n-butyl)-pinanoamine hydrochloride was conducted. Results of these studies confirm the structure of the amines obtained and the correctness of the proposed reaction pathway.Crystal data: C₁₂H₂₈NOCl,P2₁/c,a=13.196(1),b=8.562(1),c=14.276(1) Å,=110.41(3)°,R=0.034 for 2046 reflections.Part I,J. Cryst. Spec. Res. (1989)19, 535.     

X-ray analysis and spectral data of β-[N-phenyl,N-(β′-bromo-cinnamoyl)-amino]-cinnamanilide reveal the course of reaction of benzoylacetanilide with POBr3

The reaction of benzoylacetanilide with the excess of POBr₃ furnished monomolecular products and the bimolecular-[N-phenyl,N-(-bromo-cinnamoyl)-amino]-cinnamanilide. Its structure was elucidated by means of elemental analysis, IR,¹H NMR and mass spectral data as well as X-ray analysis, which proved that the reaction mentioned goes via condensation. C₃₀H₂₃BrN₂O₂ crystallizes with two independent molecules in an asymmetric unit in the orthorhombic space groupP2₁2₁2₁ witha ₃=9.834(3),b=19.614(2),c=26.450(6) Å,Z=8,V=5101(4) ų,D _m =1.34,D _x =1.36 mg m^–3,F(000)=2151,M _r =523.107,=2.25 mm^–1, (CuK)=1.54178 Å,T=293 K; the finalR factor was 0.067.     

Crystal structure ofβ-C.I. Solvent Yellow 18, 4(2′,4′-dimethylphenyl hydrazono)-5-methyl-2-phenyl-3H-pyrazol-3-one

The crystal structure of-C.I. Solvent Yellow 18, C₁₈H₁₈N₄O, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=30.948(18)Å,b=4.918(4)Å,c=20.861(9)Å,=91.68(4)°, space groupC2/c,Z=8. The structure has been solved by direct methods and least-squares refinement has been completed on three dimensional data (1237 reflections MoK radiation). The hydrogen atoms have been found but only their positional parameters refined. Final residual 0.092 (all intensity data). The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonding keeps the molecule approximately planar. The molecules are packed in columns parallel to theb axis, while the molecule lies approximately parallel to the (51¯3) plane. The molecules are linked by van der Waals' force.     

Crystal Structure of (1-Cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-4-(oxo-\κO)-3-quinolinecarboxylato-κO3) difluoro-boron

Abstract  

The complex (1-Cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-4-(oxo-\κO)-3-quinolinecarboxylato-κO3) difluoro-boron crystallizes in the monoclinic space group P2₁/c, a = 11.43400(10) ?, b = 9.16420(10) ?, c = 13.8745(2) ?, β = 106.6470(10)o, V = 1392.89(3) ?³, and Z = 4; which is a resonance hybrid with an almost tetrahedral boron which produces a 6-membered ring, where the boron atom is slightly bent out of plane.     

Crystal Structure of 3-Hydroxy-3′,4′-Methylenedioxy Flavone-6-Carboxylic Acid Dimethylformamide Solvate

Abstract  

The optically pure 3-hydroxy-3′,4′-methylenedioxy flavone-6-carboxylic acid was obtained through the chalcone route. The structure of 3-hydroxy-3′,4′-methylenedioxy flavone-6-carboxylic acid was first elucidated by single crystal X-ray analysis: triclinic, space group, triclinic (P-1) with a = 8.1379(13) ?, b = 8.9831(14) ?, c = 13.198(2) ?, α = 88.413(2)°, β = 74.908(2)°, γ = 72.987(2)°. V = 889.5(2) ?³, Z = 2. The structure was solved by direct methods and refined to a final R = 0.0413 for 1630 reflections with I > 2σ(I). The crystal structure is stabilized by O–H···O and C–H···O hydrogen bondings and π–π stacking interactions.     

Mathematical analysis of the reaction–diffusion of water in glass tubes

The diffusion and reaction of water with glass tubes are mathematically analyzed. A general mathematical model is developed that takes into account the absorption of molecular water from the vapour phase on to the glass tube surface, its subsequent diffusion, and both the forward and backward reactions of formation of the silanol groups. The general solutions are obtained numerically while analytical solutions are obtained for special cases of small time or fast reaction. An approximate integral solution is obtained for the latter and it is shown that the equilibrium model with fast reaction can be cast into a simple yet accurate algebraic form which is easy to implement. The models are applied to few cases of practical importance to optical fiber processing.     

Structural analysis of xCsCl(1 − x)Ga2S3 glasses

Sulphide glasses doped with rare-earth ions have been demonstrated to be suitable for photonic applications such as optical amplifiers, up-converters and fiber lasers. The substitution of metal halides into the glass network has been shown to result glasses with desirable properties in terms of quantum efficiency and fiber manufacture [J.R. Hector, J. Wang, D. Brady, M. Kluth, D.W. Hewak, W.S. Brocklesby, D.N. Payne, Journal of Non-Crystalline Solids 239 (1998) 176]. To assist in the understanding of this improvement a structural analysis of glasses with a composition xCsCl(1 ? x)Ga₂S₃ has been undertaken in order to examine the nature of the gallium environment. Information collected by high energy X-ray diffraction and neutron diffraction have been analyzed to permit the identification of the structural units as Ga centered tetrahedra. The interconnection between the tetrahedra was found to be predominantly corner sharing.     

Crystal and molecular structure of [H3O·18-crown-6]2-[ReCl6] isolated from a liquid clathrate medium

The crystal and molecular structure of [H₃O·18-crown-6]₂[ReCl₆]1 is reported. Crystal data for1: trigonal, space group R ,a=13.857(2) Å,c=10.154(2) Å,D _c =2.85 g/cm³,Z=3,R _f =0.073,R _w =0.064. The oxonium ion is observed to be crystallographically disordered lying 0.37 Å on both sides of the plane defined by the crown ether oxygen atoms. The anion resides on a crystallographic position forming a slightly distorted octahedron.     

Nanostructured crystals of Sr1?xRxF2+x fluorite phases and their ordering: 6. Microindentation analysis of crystals

Hardness, crack resistance, brittleness, and effective fracture energy have been studied for crystals of 24 fluorite phases Sr_{1 − x} R _x F_{2 + x} (R are 14 rare earth elements (REEs); 0 < x ≤ 0.5) and SrF2 grown by the Bridgman method from a melt. These characteristics change nonlinearly with an increase in the REE content for Sr_{1 − x} R _x F_{2 + x} (0 < x ≤ 0.5) with R = La, Nd, Sm, Gd, and Lu; it is maximum in the range x < 0.1 for all REEs. The changes in a number of REEs have been traced for an isoconcentration series of Sr_0.90 R _0.10F_2.10 crystals (R = La, Nd, Sm, Gd, Ho, Er-Lu, or Y) and crystals (similar in composition) with R = Tb and Dy. The hardness of Sr_{1 − x} R _x F_{2 + x} crystals is higher by a factor of ∼2–3 than that of SrF2. The effect of decrease in microstresses in SrF₂ crystals is confirmed by the isomorphic introduction of R ³⁺ ions into this crystalline matrix.