Characterization crystallization procedure

Ephedra spp. roots are known as major source of ephedrine and derivatives alkaloids, but this plant species also contains an imidazole derivative, feruloylhistamine (12), which was identified in methanolic extract of the drug in 1983 [19, 20]. After column chromatography and crystallization procedures, feruloylhistamine was characterized by and NMR and mass spectroscopy. A molecular ion peak was observed at miz 287 consistent to a C15H17N3O3 fragment, and the NMR spectrum revealed signals for aliphatic and aromatic carbons and also one carbonyl group. The synthetic derivative was also obtained and afforded the same physical data as the natural compound [19]. 

Syntheses, crystallization, structural identification, and chemical characterization of high nuclearity clusters can be exceedingly difficult. Usually, several different clusters are formed in any given synthetic procedure, and each compound must be extracted and identified. The problem may be compounded by the instabiUty of a particular molecule. In 1962 the stmcture of the first high nuclearity carbide complex formulated as Fe (CO) C [11087-47-1] was characterized (40,41) see stmcture (12). This complex was originally prepared in an extremely low yield of 0.5%. This molecule was the first carbide complex isolated and became the foremnner of a whole family of carbide complexes of square pyramidal stmcture and a total of 74-valence electrons (see also Carbides, survey). 

An average crystal size can be used to characterize a CSD. However, the average can be determined on any of several bases, and the basis selected must be specified for the average to be usehil. More than 20 different averaging procedures have been proposed, yet none is generally satisfactory or preferred (5). 

Benzothiadiazole 1,1-dioxide can be conveniently assayed and characterized without isolation by forming its adduct with cyclopentadiene.5 The following procedure illustrates characterization, for assay the same procedure can be applied to an aliquot, with all amounts scaled down in proportion. The dried ether extract of 1,2,3-benzothiadiazole 1,1-dioxide prepared from 1.43 g (0.0080 mole) of sodium 2-aminobenzene-sulfinate is concentrated to about 20 ml at 0°, and 20 ml. of acetonitrile at —20° is added. Twenty milliliters of cold, freshly prepared cyclopentadiene6 is added The mixture is kept overnight at —10° to 0°. Solvent and excess cyclopentadiene are removed by evaporation at 0° under reduced pressure to leave 1.20-1.28 g. (64-68% based on sodium 2-aminobenzenesulfinate) of crude 1-1 adduct, mp. 87° (dec.). For purification it is dissolved in 20 ml. of methylene chloride, 70 ml. of ether is added, and the solution is kept at —70°. Adduct decomposing at 90° crystallizes recovery is about 75%. From pure, crystalline 1, 2, 3-benzothiadiazole 1,1-dioxide the yield of adduct is 92-98%. 

It is, therefore, required that all initial compounds be dried properly prior to performing the reduction. This procedure is not at all trivial and refers, first of all, to the diluent salts, and especially to potassium fluoride, KF, which is characterized by a strong hygroscopic property and a tendency to form stable crystal hydrates. The problem of contamination due to hydrolytic processes can usually be resolved in two manners. The first is to apply another tantalum-containing complex fluoride compound that does not undergo hydrolysis. The second involves the adjustment of the reduction process parameters and use of some additives that will "collect" the oxygen present, in the form of water, hydroxyl groups or other compounds. 

Two approaches to the attainment of the oriented states of polymer solutions and melts can be distinguished. The first one consists in the orientational crystallization of flexible-chain polymers based on the fixation by subsequent crystallization of the chains obtained as a result of melt extension. This procedure ensures the formation of a highly oriented supramolecular structure in the crystallized material. The second approach is based on the use of solutions of rigid-chain polymers in which the transition to the liquid crystalline state occurs, due to a high anisometry of the macromolecules. This state is characterized by high one-dimensional chain orientation and, as a result, by the anisotropy of the main physical properties of the material. Only slight extensions are required to obtain highly oriented films and fibers from such solutions. 

Recent developments and prospects of these methods have been discussed in a chapter by Schneider et al. (2001). It was underlined that these methods are widely applied for the characterization of crystalline materials (phase identification, quantitative analysis, determination of structure imperfections, crystal structure determination and analysis of 3D microstructural properties). Phase identification was traditionally based on a comparison of observed data with interplanar spacings and relative intensities (d and T) listed for crystalline materials. More recent search-match procedures, based on digitized patterns, and Powder Diffraction File (International Centre for Diffraction Data, USA.) containing powder data for hundreds of thousands substances may result in a fast efficient qualitative analysis. The determination of the amounts of different phases present in a multi-component sample (quantitative analysis) is based on the so-called Rietveld method. Procedures for pattern indexing, structure solution and refinement of structure model are based on the same method. 

This work is aimed at establishing a preparation procedure for zirconium phosphonates not only in the single component phosphonate but also in the composite zirconium phosphonates in single crystal phase, and to establish a procedure to characterize these compounds. 

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