By X-ray methods

Composition. The results of elemental analyses are almost always included among the specifications for a commercial catalyst. Depending on the accuracy desired and whether or not the catalyst can be rendered soluble without great difficulty, elemental analysis may be performed by x-ray methods, by one of the procedures based on atomic absorption, or by traditional wet-chemical methods. Erequentiy it is important to determine and report trace element components that may have an effect on catalyst performance. 

Nearly all of the important chemical (identification of elements, purity, homogeneity, speciation) and physical (roughness, thickness, serie of the layers) parameters of such a structure can be determned non-destructively by X-ray methods (e.g., EDXRS, WDXRS, TXRS, SYXRS, g-XRS, NEXAFS). 

How well do NMR-derived stmctures agree with those determined by x-ray methods The structures of some different globular proteins that have been independently obtained by the two methods—such as bovine pancreatic... 

The elementary processes involved in this energy transfer can take place also in a sample being analyzed by x-ray methods. 

The other extreme is provided by I2, for which the transition from oscillation to rotation takes place at about n = 300. At the melting point the molecules are in states with n = 10 or 15, so that there are no rotating molecules in this crystal. This agrees with the fact that equilibrium positions for the atoms have been found by x-ray methods. 

Recently the pyridine adduct of borabenzene 5 has been synthesized as a yellow crystalline solid (26). Its structural characterization by X-ray methods provides the first structural data of an uncomplexed borabenzene... 

A compound containing both Se6+ and Se4+ species is Na2Se04 H2Se03 H20. It has been investigated by X-ray methods and vibrational spectroscopy.84 More recently, the acidic oxo-selenate(I V) KH3(Se03)2 has been reported.85... 

An analogous nitrato complex, Be40(N03)6, is known in the solid state (145). The presence of a central 4-coordinate oxide ion and bridging nitrato ions has been confirmed by X-ray methods (146). The structures of these solid-state (jl4-oxo complexes lend support to the fi.roxo structures suggested for phosphato and carbonato complexes in solution (see Section IV). 

Begley MJ, Crombie L, Simmonds DJ, et al. (1972) Absolute configuration of pyrethrins. Configuration and structure of (+)-allethronyl (+)-tra s-chrysanthemate 6-bromo-2,4-dinitrophenylhydrazone by X-ray methods. J Chem Soc Chem Commun 1276-1277... 

The 3D structures of several aminoglycoside-enzyme complexes have been described recently by X-ray methods [35,36]. Interestingly, in some cases, the 3D structure of the antibiotic in the enzyme binding site significantly... 

M.HART, in Characterization of crystal growth defects by X-ray methods, eds. B.K. 

N. Conformational Analysis of Molecules in Solution (CAMSEQ). A problem of long standing in chemistry has been to estimate the relationship between the conformation of a molecule in the crystal, as measured by X-ray methods, with that in solution where barriers to rotation are greatly reduced. A sophisticated program set for Conformational Analysis of Molecules in Solution by Empirical and Quantum-mechanical methods (CAMSEQ) has been developed for this purpose by Hopfinger and co-workers [l2] at Case Western Reserve University. 

Iron(ii) complexes of ethylenedithiodiacetic acid, diethylenetrithioacetic acid, and ethylenetetrathiotetra-acetic acid have all been reported. " " Isonitrile and other complexes. Refluxing [Fe(CNMe) ](HSOj2 "hh excess methylamine for 12 h in methanol gives the cation [Fe(CNMe)gNH2Me] which can be precipitated as its PF salt. " The structure of this cation has been determined by X-ray methods and is shown in (52). The location of the protons was confirmed by n.m.r. and the suggested mechanism of formation is as shown. 

Other Complexes. Co2(CO)g reacts with Ph2PC=C(CF3) in benzene to yield (62). the structure of which has been determined by X-ray methods. The... 

The structure of 1,1-difluorobenzocyclopropene (21), as determined by micro-wave spectroscopy, exhibits some deviations from that determined by X-ray methods. The discrepancies may be due to the fact that the microwave spectrum was only measured from a single isotopomer, since at the time, no isotopically... 

A feature of these acidic antibiotics is that their chemical constitutions were established by crystal structure analysis, having defied classical organic chemistry, even aided by spectroscopic techniques. The reason for this is apparent from the formulae, (X)—(XII), examples chosen because the heavy atom salts are isomorphous with those of alkali metals. The formulae show the correct absolute configurations as determined by X-ray methods. 

The isomerization between N- and (9-acylated benzotriazol-l-ols and 1,2,3-triazol-l-ols has been extensively studied (see Section 4.01.7.1) in part by x-ray methods. The aroyl group position is established by x-ray crystallographic analyses because the N- and (9-acylated forms are not readily distinguished by spectral methods. X-ray analyses of l-(4-nitrobenzoyloxy)-1,2,3-triazole (19a) <93AX(C)49>, l-(4-chlorobenzoyloxy)-l,2,3-triazole (19b) <88AX(C)1063>, and 1-benzoyloxy-... 

The crystal and molecular structures of 5-phenyl-l,2,3,4-thiatriazole (7) and its 3-oxide (8) and 3-ethyl (9) derivatives have been determined by x-ray methods <76ACS(A)35l>. Selected values are given in Figure 2. 

Elemental composition Ba 81.08%, S 18.92%. The metal may be analyzed by various instrumental techniques (see Barium). In the powder form, the compound may be identified by x-ray methods. In solution, it undergoes hydrolysis forming barium hydroxide and hydrosulfide. The former is neutralized by acid titration to a pH of 8.4 while the hydrosulfide is titrated with acid to pH 4.2 for neutralization. 

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