The Crystal Structure and Molecular Conformation of 3,7-Dichlorophenoselenazine

The crystal structure of SeC12NCI2H7 has been solved by Patterson and Fourier methods and refined to an R of 7-5 % by full-matrix least-squares methods. The unit cell is orthorhombic, with a-- 7-995 (3), b = 23.808 (1), c = 6.028 (2)/~, and four molecules in the cell. The space group is Pnma. The structure contains layers of molecules centred on the mirror planes at b/4 and 3b/4

The Structure of l-Phenyl-4,5-(l,2-D-glucofurano)imidazolidin-2-one

The crystal structure of Cl3Ht6N20 5 has been solved by direct methods. Crystal data are a -- 9.033 (1), b -- 10.097 (1), c -- 7.155 (1)A, fl= 105.92 (1) °, Z -- 2, space group P21 (from statistics). The final R value for 1246 independent reflexions was 0.068. The glucofurano- imidazolidine group adopts a cis form of coupling with a dihedral angle of 70.2 (6) °. The phenyl substituent forms a dihedral angle of 15.1 (6) ° with the imidazolidine ring plane. Intermolecular hydrogen bonds link molecules related by a screw axis to give helical chains parallel to b

The Conformation and Crystal Structure of meso-2,10-Dimethyl- 3,1 l-dimethoxycarbonyl- 1,6,9,13-tetraoxadispiro[4.2.4.2]tetradeca-2,10-diene

The crystal and molecular structure of the title compound, C16H20Os, has been determined by singlecrystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2t/c with two molecules in a cell of dimensions a = 9.199 (1), b = 12.423 (1), c = 8.047 (1) A, and fl = 114.87 (1) °. The structure was solved by direct methods (MULTAN). Full-matrix least-squares refinement gave a final agreement index of R = 0.054 for 1166 observed reflections. The sixmembered ring adopts the chair conformation around a symmetry centre. The conformation of the fivemembered rings is nearer to a twist than to an envelope, the approximate twofold axis passing through the C(4) atom. The endocyclic C-O bonds are asymmetric and the C=C distance is longer than expected for a double bond. Crystal packing is due to van der Waals interactions only

Structure and Molecular Conformation of l-(4-Acetyl-5-methyl-2-furyl)- 1,3-dideoxy-3-nitro-fl-D-xylopyranose

The crystal structure of C I2HIsNO7 has been determined at room temperature. Crystals are tetragonal, space group P432~2, Z = 8, with a -- 12.039 (1), c = 17.979 (4)A. 1304 observed reflexions contributed to the full-matrix least-squares refinement to give R -- 0.075. The pyranose ring displays a slightly distorted chair with 4C~ conformation and all the substituents (furanose ring, NO 2 and OH groups) are equatorial. The reported configuration can be considered as the absolute configuration from the absence of epimerization at the anomeric atom. The packing of the structure can be described by a three-dimensional hydrogen-bonding scheme

The Crystal and Molecular Structure of 4-Formylimidazoline-2-thione

The title compound is monoclinic, space group P2 Jc, with a = 4.020 (4), b = 21.491(3), c = 7-410 (4) ,4,, fl = 124.1 (5) °, Z = 4. The structure was solved by Patterson-function and heavy-atom methods from diffractometer X-ray data. The final R value is 0.040. All the atoms lie approximately on the least-squares plane of the imidazoline ring. The molecules related by the glide plane are linked by N-H... O hydrogen bonds (2.840 ,~) to form a chain along e. The chains are held together by N-H... S hydrogen bonds (3.260 A) between the molecules related by an inversion centre

Structure of 4-(~-D-Erythrofuranosyl)-3-methyl- l-(p-tolyl)-4-imidazoline-2-thione Monohydrate, C 15H18N203S.H20

Mr=324.4, orthorhombic, P212t2 ~, a= 32.150(5), b=10.215(1), c=4.805(1)A, V= 1578.0 (4)/~3, Z = 4, D x = 1.36 Mg m -a, 2(Cu Ka) = 1.5418A, #=1.953mm -1, T=300K, final R= 0.050 for 1361 observed [I>2tr(I)] independent reflexions. The sugar ring adopts a conformation intermediate between envelope 2E and twist 2T forms. The orientation of the imidazoline ring with respect to the furanose is anti; the glycosidic angle is 24.6 (7) °. The crystal packing is due to hydrogen bonds involving the hydration water molecules

Lattice Dynamical Calculation of First-Order Thermal Diffuse Scattering in Phenothiazine

A computer program has been developed to calculate first-order thermal diffuse scattering (TDS) intensity from eigenvectors and eigenvalues of the dynamical matrix obtained within the harmonic approximation with an atom-atom potential function and the external Born-yon Kfirmfin formalism. It is applied to monoclinic phenothiazine and correction factors of Bragg intensities due to TDS contribution are calculated and compared with the long-wave approximation. A Fourier difference synthesis is performed in order to reveal the influence of TDS contributions in electron density maps. A least-squares process is carried out to obtain the changes in structural parameters due to TDS contribution

Lattice Dynamics and Thermal Crystallographic Parameters in Phenothiazine

A computer program has been developed to study the lattice dynamics of molecular crystals in the harmonic approximation with the external Born-yon KS.rm~n formalism and an atom-atom potential function. Dispersion curves are obtained for monoclinic phenothiazine together with frequency distribution functions and external mode contribution to thermodynamic functions. Lattice dynamical T, L and S rigid-body tensors are obtained and individual thermal tensors are compared with experiment. The disagreement with respect to experimental results is of the same order as the disagreement with a Schomaker-Trueblood fit of experimental data

Lattice-Dynamical Calculation of Second-Order Thermal Diffuse Scattering in Molecular Crystals

A computer procedure has been developed to calculate second-order thermal diffuse scattering (TDS) intensity for molecular crystals from latticedynamical calculations with an atom-atom potential in the Born-von K~irmfin formalism. It is applied to monoclinic phenothiazine and different contributions to second-order TDS intensity, acoustic-acoustic, acoustic-optic and optic-optic, are compared. Calculations are also performed in the long-wave approximation allowing for dispersion (LWD) and correction factors of Bragg intensities due to TDS contribution in the LWD approximation are, generally but not always, lower than lattice-dynamical ones; the ratio between LWD and 'exact' factors ranges from 0.4 to 1.4 for reflections considered

Structure of 1,3-Dihydro-4-[(2R)-2,5-dihydro-2-furyl]-3-phenyl-l-(p-tolyl)-2H-imidazole- 2-thione, C20HlsN2OS

Mr=334.4, orthorhombic, P212~2 ~, a= 9.366(4), b=20.616(5), c=9.137(4)A, V= 1764 (1) A 3, Z = 4, D x = 1.26 Mg m -3, 2(Mo Ka) = 0.7107 A, g = 0.18 mm -~, F(000) = 704, T= 300 K, final R--0.056 (wR =0.052) for 1979 observed reflections [I > 2a(/)]. The furanose ring is approximately planar because of the double bond, 1.289 (9) A, which affects the conformation of the ring. The dihedral angle between the furanose and imidazole least-squares planes is 69.9 (2) °. A possible C--H...O hydrogen bond has been detected involving C and O atoms in the furanose ring, giving infinite helical chains along [001 ]