X-ray-diffraction analysis

This is, for instance, the case of the a and 5 forms of PVDF (also called form II and form lip, that is form II polarized), both contain chains with a TG+TG" conformation and have an orthorhombic unit cell with substantially identical dimensions [30, 31]. Detailed X-ray diffraction analyses have shown that the two chains in the unit cells are with the dipole vectors pointing in opposite directions in the a form, while they are in the same direction in the 8 form [32],... 

Sulfoxides form adducts with Lewis acids like SbCls and SnCU [80]. In the case of SsO the crystalline products SsO-SbCh [81] and (SsO)2-SnCl4 [82] have been prepared and characterized by single crystal X-ray diffraction analyses. Reaction of SsO with SbCls in CS2 at 20 °C and subsequent cooling of the solution to -50 °C resulted in orange orthorhombic crystals of SsO-SbCls in 71% yield. These molecules are of Cg symmetry see Fig.6 [81]. 

Chiang and coworkers synthesized a dimer of compound 26 in which two diiron subunits are linked by two azadithiolate ligands as a model of the active site for the [FeFeJ-hydrogenase [203]. Protonation of 26 afforded the p-hydride complex [26-2H 2H ] via the initially protonated spieces [26-2H ] (Scheme 62). These three complexes were also characterized by the X-ray diffraction analyses. H2-generation was observed by electrochemical reduction of protons catalyzed by 26 in the presence of HBF4 as a proton source. It was experimentally ascertained that [26-2H 2H ] was converted into 26 by four irreversible reduction steps in the absence of HBF4. 

In the reaction of lactic acid to form pyruvic acid over the iron phosphate catalysts, formation of a new compound was observed. As the extent of reaction increased, the amount of pyruvic acid increased to a maximum and then decreased, while that of the new compound increased steadily. It was therefore concluded that the new compound is formed from pyruvic acid in parallel with acetic acid and CO2. According to gas-mass analyses, the molecular weight was determined as 112. However, there are many compounds with molecular weigth of 112. After the NMR analyses and X-ray diffraction analyses for the single crystal, the new compound was determined to be citraconic anhydride, i.e., mono-methyl maleic anhydride. 

Compounds Which Have Not Been Investigated by Single Crystal X-ray Diffraction Analyses... 

The techniques of X-ray diffraction analyses of crystals of compounds of interest can be used to determine, with high precision, the three-dimensional arrangement of atoms, ions and molecules in such crystals (14) in each case the result is referred to as the "crystal structure." X-ray diffraction by crystals was discovered by von Laue, Friedrich and Knipping (15) and the technique was applied by the Braggs to the determination of the structures of... 

X-ray diffraction analyses revealed a practically planar crystal structure of diphenyl-DPP with the phenyl rings twisted by only 7° out of the plane of the... 

The complex between 20 and maleic acid reveals114 (by X-ray diffraction analyses of single crystals) the presence of two intermolecular hydrogen bonds between the —NH3+ group and the anion. 

X-ray diffraction analyses revealed isostructural geometries for all trinuclear complexes, where three metal ions are coordinated to two ligand molecules (Fig. 7). Each metal ion is coordinated to two carbenoid carbon atoms each from a different ligand. The structure exhibits a Ds symmetry with the 3-fold axis passing through the anchoring C atoms of the two ligands. 

X-Ray diffraction analyses of vincristine methiodide (39) and vinzoli-dine 1-naphthalene sulfonate (40) provide atomic coordinates of compounds that are either modified in the velbanamine portion (alkylation at N-6, Fig. 3) or in the vindoline portion (a spiro-fused oxazolidinedione at C-3 and C-23, Fig. 4). These structures show a chair-boat conformation for ring C with C-8 exhibiting an endo pucker. Ring D is clearly in a chair conformation, but, in contrast to the conclusions drawn from C-NMR studies, the N-6 -C-7 bond is axial relative to the piperidine ring. 

Effect of Steam Treatment. X-ray diffraction analyses indicated that ZSM-5 retained in excess of 90% of its crystallinity after the steam treatment described in the methods section. Unit cell constant of the REY zeolite in Super-D declined from 24.658. to 24.38a due to the steam treatment. Independent measurements... 

We thank P. Bowen for initial fabrication of the water manifolds in the system. Most of the fabrication of the equipment was done by R. Flores who also performed some of the initial flow tests on the peristaltic pumps. J. Bushman and M. Edwards modified and maintained the equipment W. Beiriger performed the x-ray diffraction analyses C. Slettevold and A. Biermann performed the particle analysis and determined the surface area on the samples. J. Wittmayer took the SEM photos. We also thank L, Gazlay and D. Hosmer for the gamma-ray spectroscopy analysis,... 

In order to substantiate further the mineral matter content information received from the x-ray diffraction analyses, several coke pellets were scanned for sulfur, iron, calcium, silicon, aluminum and potassium in the electron microprobe. Electron probe results showed abundant silicon, suggesting quartz (Si02), considerable aluminum, suggesting kaolinite [Ali>Sii Oii(OH)4] and, relatively speaking, little iron, sulfur, calcium, or potassium. 

As for cis- and trans- l-(9-anthryl)-2-phenylethylenes (9-styrylanthra-cenes) 68a and 69a, differences in their ground state molecular geometry in terms of angles between the planes of the three jt-systems, viz. anthracene, ethylene, and phenyl, as revealed by X-ray diffraction analyses, are relatively small (see Table 14). The major geometrical difference between the two isomers is found in the angle between the anthracene and ethylene ir-systems. 

According to the concept of Stach/Poldinger91 and Wilhelm92, such alterations in stereochemical structure should result in changed psychotropic activities. To check this theory, comparative X-ray diffraction analyses and comparative biological tests are under investigation. 

X-ray diffraction analyses of some tricyclic silicon containing compounds with potential psychotropic activity have been carried out93, 100, 101 The experimental dihedral angles a are summarized in Table 12. 

The results of single-crystal X-ray diffraction analyses of polychalcogenadisilabicyclo-[k.l.m]alkanes are summarized in Figures 6 and 7 and Tables 5 and 6. 

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