X-ray crystallographic determination of the structure and conformation of trans-2-tribromomethyl-5-trichloromethyl-1,3-dioxolan-4-one: an analogue of chloralide

trans-2-Tribromomethyl-5-trichloromethyl-1,3-dioxolan-4-one is monoclinic,P2₁/c,a=6.381(6),b=17.116(6),c=10.598(5) Å,=94.07(6)°,Z=4. The structure was solved by direct methods from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by full-matrix least squares to a finalR value of 0.042 using 1274 reflections. The conformation of the molecule is very similar to that of chloralide with the 5-mem-bered ring being almost planar. Evidence is provided for a possible C-HO intermolecular interaction. The average C-Br distance is 1.931(11) Å and the average Br-C-Br angle is 109.7(9)°. A table of average C-Br bond lengths and Br-C-Br angles, with the ranges for these parameters, in compounds containing -CBr₃ groups is given. Some¹H NMR and mass spectra data are included for the title compound and for chloralide.     

Structure and conformation of 6-nitro-2-trichloromethyl-1,3-benzdioxin-4-one: X-ray crystallographic determination

6-nitro-2-trichloromethyl-1,3-benzdioxin-4-one is monoclinic,P2₁/n;a=5.969(2),b=11.646(1),c=16.953(1) Å;=98.03(2)°;Z=4. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least squares to a finalR value of 0.030 using 1530 reflections.The heterocyclic ring is a distorted half-boat and is substituted equatorially by a trichloromethyl group. Dihedral angles are (a) 4.87(7)° between the mean plane of the aromatic ring and the plane containing the two carbon atoms common to both rings plus the two atoms bonded to these, and (b) 16.8(2)° between the carbonyl group and the aromatic ring. The conformation is discussed with reference to the two previously reported X-ray structures of 1,3-benzdioxin-4-ones and to two isocoumarins.     

Structure and conformation of 6-nitro-2-trichloromethyl-4-dichloromethylene-1,3-benzdioxin: X-ray crystallographic determination

6-Nitro-trichloromethy1-4-dichloromethylene-1,3-benzdioxin is monoclinic,C2/c,a=12.906(2) Å,b=19.957(2) Å,c=19.992(2) Å,=99.05(1)°,Z=8. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least squares to a finalR value of 0.032 using 1838 reflections.The compound exhibits a distorted envelope structure in the dioxin ring, and the trichloromethyl group is in the equatorial position. The angle between the planes each containing a group of three atoms from either end of the double bond of the:C(ring)=CCl₂ moiety is 3.8(2)°: a short discussion of deformations found in other compounds which contain:C(ring)=CC1₂ in light atom structures is given. The benzene ring is slightly puckered and planarity has been retained about the carbon atoms which are common to both rings.     

Structure and conformation of 6,8-dinitro-2,4-bis(trichloromethyl)-1,3-benzdioxin: X-ray crystallographic determination

6,8-dinitro-2,4-bis(trichloromethyl)-1,3-benzdioxin is monoclinic,P2₁/c,Z=4,a=12.348(2),b=11.575(3),c=12.183(4) Å,=107.48(2)°. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least-squares to a finalR value of 0.032 using 2192 reflections. The heterocyclic ring is an envelope structure, the dihedral angle between the plane of the aromatic ring and that containing five of the atoms of the heterocycle being 4.98(6)°. One -CCl₃ group is pseudoequatorial while the (Ar-C)CCl₃ group is pseudoaxial. C-C_eq 1.526(3) Å; C-C_ax 1.537(3) Å; C-C(C_ax)-O 112.4(2)°; C(C_ax)-O-C(C_eq) 115.2(2)°.     

Structure and conformation of 6-nitro-2,4-bis(trichloromethyl)-1,3-benzdioxin: X-ray crystallographic determination

6-Nitro-2,4-bis(trichloromethyl)-1,3-benzdioxin is triclinic,P¯1;a=6.604(2),b=7.678(6),c=15.201(4) Å; =91.57(5),=99.39(2), =90.50(5)°;Z=2. The structure was solved by direct methods from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer and refined by least squares to a finalR value of 0.035 using 2092 reflections.The molecule consists of a heterocycle in a distorted screw boat conformation fused to a significantly nonplanar aromatic ring. One-CCl₃ group is pseudoequatorial while the (Ar-C)CCl₃ group is pseudoaxial. The C_Ar-C-O-C side of the ring is much flatter than the C_Ar-C_Ar-O-C side, the distortion being caused by the necessity of the-C_axCl₃ group to bend away from the heterocycle. C-C_eq 1.532(4) Å; C-C_ax 1.550(4) Å; C-C(C_ax)-O 113.0(3)°; C(C_ax)-O-C(C_eq) 115.5(2)°.     

X-ray crystallographic determination of the structure and conformation of 7-(1-acetoxy-1-methylethyl)-4a-methyl-octahydro-2(3H)-naphthalenone

The crystal structure of 7-(1-acetoxy-1-methylethyl)-4a-methyl-octahydro-2(³H)-naphthalenone, C₁₆H₂₄O₃ has been determined by X-ray diffraction. The crystals are orthorhombic, P2₁2₁2₁,a=5.938(2),b=12.081(4),c=21.607(7) Å,Z=4. The structure was solved by direct methods, and refined to an R value of 0.062 for 1013 nonzero independent amplitudes. Ring A has the C(6) distorted sofa conformation whereas the B ring possesses the slightly deformed chair conformation. The side chain in the C(10) position is oriented in relation to the plane of the B ring.The nomenclature of IUPAC for the name of compound in the title is applied. However, for simplicity reason numbers of atoms in the paper follow Fig. 1.     

X-ray crystallographic determination of the structure and conformation of 1,4,4-trimethyltricyclo[5.4.0.03,5]-undec-7-en-9-one and 1,4,4,8-tetramethyltricyclo[5.4.0.03,5]-undec-T-en-9-one

The crystal structure and conformation of 1,4,4-trimethyltricyclo[5.4.0.0^3,5]undec-7-en-9-one (I) and 1,4,4,8-tetramethyltricyclo[5.4.0.0^3,5]undec-7-en-9-one (II) have been determined by X-ray diffraction. In both cases the crystals are orthorhombic, P2₁2₁2₁,a=6.194 (2) (I); 7.499 (2) (II),b=7.486 (3) (I); 12.855 (3) (II),c=26.283 (7) (I); 13.928 (4) (II) Å,Z=4. The structure was solved by direct methods, and refined to anR value of 0.048 for 1534 (I) and 0.054 for 1357 (II) withI>3.0 (I). In both compounds substituted by carbonyl group ring has the distorted³E sofa conformation whereas the second one possesses the slightly deformed^7.10B boat conformation.The nomenclature of IUPAC for the name of compounds in the title is applied. However, for simplicity the numbering of the atoms in the paper follow Fig. 1a and 1b.     

X-ray structure and conformation of some enol acetates derived from simple ketones

The conformational arrangements of a series of enol acetates derived from simple ketones have been examined by X-ray crystallography. For this series, the carbonyl enol motif was found to adopt a similar conformation.     

X-ray crystallographic structure of the 9,10-dihydro-11,12bis[(1,3,3-trimethylureido)methyl]-9,10ethanoanthracene dihydrate

As a part of studies on MDR reversal agents, structure of the 9,10-dihydro-11,12-bis[(1,3,3-trimethylureido)methyl]-9,10-ethanoanthracene dihydrate is reported. Crystal data: C₂₆H₃₄N₄O₂ × 2 H₂O; mol. mass 470.60; monoclinic; space group: C2/c, a = 15.7492(6) Å; b = 7.2245(3) Å; c = 24.3442(10) Å; β = 106.795(2)^∘; V = 2651.73(22) ų; z = 4; dx = 1.179 mg/m³; μ = 0.64 mm⁻¹; F(000) = 1016; final R = 0.061 for 2501 reflections [I > 4 σ (I)]. Only half of the molecule is unique. The two nonplanar rings from the independent part of 9,10-dihydro-9,10-ethanoanthracene adopt a boat conformation. Crystallographic data demonstrate the “syn-syn” conformation of urea substituents in the molecule. In the crystal, water molecules are linked to the main species by H-bonds: O3′⋅sH12w—O1—H11w⋅sO3′(1.5 − x, 0.5 − y, 1 − z).     

X-ray structure and conformation of some (R,R)-N,N′-tetrasubsubstituted 1,2-diamines

The conformational arrangement of a series of (R,R)-N,N′-tetrasubstituted cyclohexyl-1,2-diamines have been examined by X-ray crystallography.     

Synthesis and X-ray structure of new 5-amino-methyl-4-isoxazolecarboxylic acid azides

The syntheses of the new heterocyclic azides which open a number ways of obtaining interesting isoxazole derivatives has been described. Chemical, spectral and X-ray data giving the evidence of the structure of these compounds are presented. X-ray studies were carried out on compoundsI,II(C₅H₅N₅O₂, C₁₂H₉N₅O₃) witha=3.775(2), 7.179(3);b=11.593(3), 8.135(3);c=8.443(3), 11.610(3);Z=2, 2 and space group Pn, . The structure was established using direct methods and refined by weighted full-matrix least squares. The refinement, based on 687 reflections forI, and 1648 forII withI>/ 3.0 (I), converged to a finalR of 0.333, 0.034 andR _w=0.036, 0.032.     

Synthesis, spectroscopic characterization and X-ray structure determination of tetrabutylammonium trans-diamminetetranitrocobaltate(III)

The cobalt(III) complex salt [(C₄H₉)₄N][trans-Co(NH₃)₂(NO₂)₄] has been synthesized in high yield by reacting equimolar quantities of [(C₄H₉)₄N]Br and K[trans-Co(NH₃)₂(NO₂)₄] in aqueous medium at room temperature. The product thus formed has been re-crystallised from acetone-water mixture, in the monoclinic space group P 2₁/n, with cell dimensions a=11.651(3) ?, b=19.005(4) ?, c=11.733(5) ?, β=90.28(3)°. The X-ray structure determination revealed the presence of discrete ions, [(C₄H₉)₄N]⁺ and [trans-Co(NH₃)₂(NO₂)₄]⁻. The central metal ion cobalt(III) in the anion is found in octahedral environment, in trans geometry, while the organic counterion is a quaternary alkylammonium cation. The crystal lattice is stabilized by electrostatic interactions between the cations and anions.Supplementary material Crystallographic data (excluding structure factors) for the structure(s) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC 291300. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (44) 1223 336-033; e-mail: deposit@ccdc.cam.ac.uk.     

X-ray diffraction and X-ray standing-wave study of the lead stearate film structure

A new approach to the study of the structural quality of crystals is proposed. It is based on the use of X-ray standing-wave method without measuring secondary processes and considers the multiwave interaction of diffraction reflections corresponding to different harmonics of the same crystallographic reflection. A theory of multiwave X-ray diffraction is developed to calculate the rocking curves in the X-ray diffraction scheme under consideration for a long-period quasi-one-dimensional crystal. This phase-sensitive method is used to study the structure of a multilayer lead stearate film on a silicon substrate. Some specific structural features are revealed for the surface layer of the thin film, which are most likely due to the tilt of the upper layer molecules with respect to the external normal to the film surface.     

X-ray structure determination of a chiral synthon,essential for the synthesis of 25-2H-stigmasterol

Synthesis of sterols with varying side chains, including deuterium labeled stigmasterol and sitosterol may be performed via the Wittig-Horner coupling of a 22 aldehyde derived from stigmasterol and a suitable sulfoxide derivative of the side chain. The X-ray structure determination of this synthon have been performed since it is a crucial step in order to know the absolute configuration of the chiral carbon atoms. Crystallographic data were as follows:a=7.437(2),b=10.103(4),c=10.274(3)Å, =100.32(6)^o, =759.4 ų, space group P2₁ (No.4),Z=2,D _c=1.239 g cm^–3.     

Synthesis and X-ray crystal structure determination of N-p-methylphenyl-4-benzoyl-3,4-diphenyl-2-azetidinone

The title compound, C₂₉H₂₃NO₂, has been characterized by single-crystal X-ray diffraction at two different temperatures (303 K and 120 K) and wavelengths (MoK _α and CuK _α). The non-centrosymmetric hexagonal crystal structure contains four-membered planar β-lactam ring with an unusually long C-C bond. The β-lactam ring is almost planar.     

Crystal growth and structure determination of the new silicate K3ScSi2O7

Single crystals of the new three-dimensional silicate K₃ScSi₂O₇ were obtained via a high temperature flux method and characterized by single crystal X-ray diffraction. K₃ScSi₂O₇ crystallizes in the space group P6₃/mmc with a = 5.60650(10) Å, c = 13.6420(4) Å. The structure contains sheets of ScO₆ octahedra that are connected via Si₂O₇ bridging groups.     

Characterization of the structure of porous germanium layers by high-resolution X-ray diffractometry

The surface morphology and the structure of porous germanium layers obtained by chemical etching of n-type single-crystal Ge(111) substrates with their subsequent annealing in hydrogen atmosphere are studied by high-resolution X-ray diffractometry. It is established that upon etching a 1.5 to 2.0-μm-thick porous germanium layer is formed, which contains quasi-ordered microinhomogeneities in the form of elongated pits with characteristic dimensions of 1 μm and an average distance between them of 3–4 μm. The layer bulk has pores with radii ranging within 25–30 nm and nanocrystallites with an average size of 10 nm, with the average porosity being 56%.     

Crystal structure of a salt of the pyridinium-pyridine ion by X-ray and neutron diffraction

The crystal structure of [(C₅H₅N)₂H]⁺[ZnBr_3/2Cl_3/2(C₅H₅N)]^– has been determined and refined by full-matrix least-squares methods using X-ray (R, on ¦F _o¦, = 0.045 with 2291 reflections) and neutron (¯R, on ¦F _o¦, = 0.035 with 2030 reflections) diffraction data. The crystals of the compound are monoclinic, space groupP2₁/c witha = 12.728(1),b = 11.600(1),c = 13.354(1) Å, = 107.38(1) °,Z = 4,D _x = 1.68, andD _m(flotation) = 1.69 g cm^–3. The X-ray and neutron intensities were measured by the counter -2 scan technique with CuK X-rays ( = 1.5418 Å) and neutrons with = 1.109 Å, respectively. An intramolecular N--H hydrogen bond holds pairs of pyridine molecules together in the lattice [N N, 2.737(3) Å]. The hydrogen atom is very asymmetrically disposed with N-H distances of 1.086(7) Å and 1.658(6) Å. The coordination about the zinc atom is tetrahedral with the nitrogen atom of the pyridine molecule in one tetrahedral position and different mixtures of the two halogen atoms in the other three positions. The important average bond distances from the neutron study are Zn-N [2.073(3) Å], Zn-Cl [2.251(2) Å], Zn-Br [2.394(3) Å], N-C [1.334(5) Å], C-C [1.378(5) Å], and C-H [1.075(7) Å].     

X-ray diffraction effects from 2H crystals undergoing transformation to the 4H structure by the shear mechanism

The 2H or ABAB… structure may be transformed to the 4H or ABCB… structure if deformation faults occur in a non-random manner. The theory of X-ray diffraction from one-dimensionally disordered crystals undergoing the 2H → 4H structural transformation by the deformation mechanism is developed. For this it is necessary to consider that the faults are not distributed entirely at random but tend to occur in such a manner as to statistically create a 4H structure. The X-ray diffraction effects are predicted.