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排序方式: 共有311条查询结果,搜索用时 218 毫秒
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A QSPR study of the 31P NMR chemical shifts of phosphines 总被引:3,自引:0,他引:3
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Extended Hartree-Fock (EHF ) equations are developed for the general open-shell case using a modified pair-orthogonality-constrained variation (POCV ) method. The EHF energy is expressed in terms of corresponding orbitals that are required to remain orthogonal and paired for all arbitrary infinitesimal variations. The Euler equations for each set of orbitals are reduced to unique pseudosecular equations, the LCAO form of which may easily be derived. The Euler equations and the expressions obtained for the off-diagonal elements of the ?γδ (γ, δ = a or b) matrices for the closed-shell case are identical to those obtained by Mayer, who used the generalized Brillouin theorem method. However, the present method yields equations for both closed- and open-shell cases and for any spin state. 相似文献
5.
Daniela Schlemmer E. R. de Oliveira M. J. Araújo Sales 《Journal of Thermal Analysis and Calorimetry》2007,87(3):635-638
Conventional plastics has a
large impact in increasing the environment’s pollution. That’s
why the interest has turned towards novel partially and completely biodegradable
polymers. In this work, blends of polystyrene and thermoplastic starch with
glycerol and Buriti (Mauritia flexuosa
L.) oil as plasticizers were prepared. Samples were analyzed using TG/DTG
and DSC techniques. The TG results indicated that the blends with Buriti oil
are thermally more stable than those with glycerol. The DSC analysis that
Buriti oil provides a higher degree of plasticization of PS, compared to the
blends plasticized using glycerol under the studied conditions. 相似文献
6.
Summary The action of dpe or PPh3 on dimetallated benzalazines in presence of NaClO4 gives to ionic compounds only with dpe. can be obtained from [Pd(p-XC6H3CH=N-)Cl(PPh3)2]2 and AgClO4. 相似文献
7.
Chromatographic evaluations of a C18 dimethylurea phase in 150 mm x 3.9 mm HPLC columns were performed using the Tanaka and Engelhardt test mixtures. The applicability of the new C18 dimethylurea phase was also evaluated with a mixture of some herbicides and their metabolites. An artificial aging procedure was also performed by passing a potassium phosphate mobile phase buffered at pH 7.0 through C18 50 mm x 3.9 mm dimethylurea columns. The column stability was evaluated by means of the chromatographic parameters obtained for the separation of some compounds from the Neue test mixture, using apolar, polar and highly basic analytes. 相似文献
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[reaction: see text] The reaction of alpha-alkoxy aldehydes with Et4NAg(CN)2 or Me3SiCN in the presence of MgBr2 x OEt2 in CH2Cl2 at 0 degrees C gives the corresponding syn cyanohydrins in good yield with high diastereoselectivity. Excess MgBr2 x OEt2 (typically 5 equiv) is required for high diastereoselectivity. Et4NAg(CN)2 (but not Me3SiCN) is sufficiently reactive to give cyanohydrins at -78 degrees C, and higher diastereoselectivity is obtained at this temperature. 相似文献