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51.
The solubility products for some rare earth hydroxides and their temperature dependence have been shown. Greater solubility is shown for larger atomic radii and for lower temperature. 相似文献
52.
Maprotiline determination in blood serum samples was investigated by the use of both capillary isotachophoresis and spectrofluorimetric techniques. The analyte had to be enriched before determination and extraction with n-heptane was used for this purpose. The preliminary separation enabled the determination of maprotiline in blood serum at therapeutic concentration levels. 相似文献
53.
Ernest Wenkert Edward W. Hagaman Nicole Kunesch Nai-yi Wang Bla Zsadon 《Helvetica chimica acta》1976,59(8):2711-2723
The 13C shifts of 16α- and 16β-substituted derivatives of quebrachamine, 14,15-dehydroquebrachamine, cleavamine, 15,20α-dihydrocleavamine and 15,20β-dihydrocleavamine are determined and correlated with possible conformations of these tetracycles. The method of analysis of the C(16) configuration of these compounds, which emanated from this study, is used for the determination of the configuration of the site of coupling of vindoline and cleavamine β-chloroindolenine. 相似文献
54.
The photocyclization to benzocyclobutenols of o-alkyl aromatic aldehydes that are predestined for gamma-hydrogen abstraction is found to occur efficiently in the solid state; in contrast, solution-phase photolysis is known to afford a mixture of several products. It is shown that mesitaldehyde, which is a liquid, also undergoes efficient cyclization when subjected to photolysis as a solid inclusion complex. The marginal energy differences in the relative energies of the E-enols and the corresponding cyclobutenols in the case of cyano-substituted mesitaldehydes has permitted direct observation, for the first time, of the E-enols en route to benzocyclobutenols. The AM1 calculations suggest that the cyano-substitution causes intrinsic stabilization of the E-enols relative to the corresponding cyclobutenols, while the bromo groups do the opposite. The lack of observation of the red color in bromo- and formyl-substituted aldehydes is attributed to rapid cyclization of the E-enols to the their respective cyclobutenols even at low temperatures. 相似文献
55.
Amperometric urea biosensor based on urease and electropolymerized toluidine blue dye as a pH-sensitive redox probe 总被引:4,自引:0,他引:4
Vostiar I Tkac J Sturdik E Gemeiner P 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,56(1-2):113-115
The electropolymerized toluidine blue film deposited on the glassy carbon electrode show amperometrically detectable pH sensitivity. This feature of polytoluidine blue (PTOB) film was used for a construction of an amperometric urea biosensor. We have observed a linear shift of the formal redox potential with increasing pH value between 4 and 8 giving the slope of 81 mV(Delta) pH(-1). Polytoluidine blue film has had a significantly increased stability and higher electrochemical activity compared to the adsorbed monomeric dye. The polytoluidine blue urea biosensor has been operating at a working potential of -200 mV vs. SCE. The sensitivity of the biosensor was 980 nA mM(-1) cm(-2). The biosensor showed linearity in concentration range up to 0.8 mM with the detection limit of 0.02 mM (S/N=3). 相似文献
56.
Teplý F Stará IG Starý I Kollárovic A Saman D Vyskocil S Fiedler P 《The Journal of organic chemistry》2003,68(13):5193-5197
A nonphotochemical synthetic route to 3-hexahelicenol is reported. It involves a key [2+2+2] cycloisomerization of CH(3)O-substituted triyne that is readily available from 1-methoxy-3-methylbenzene and 1-bromo-2-(bromomethyl)naphthalene. Further functional group transformations led to 3-CO(2)CH(3), 3-NH(2), 3-PPh(2), and 3-SC(O)N(CH(3))(2) substituted hexahelicenes. 相似文献
57.
Ludvík Beneš Klára Melánová Vítězslav Zima Jaroslava Kalousová Jiří Votinský 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(3):275-286
Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii). 相似文献
58.
Diane C. Rawlings Martin Gouterman Ernest R. Davidson David Feller 《International journal of quantum chemistry》1985,28(6):823-842
Ab initio CI calculations are reported on the lowest doublet, quartet, and sextet states of [FeIII(P)(NH3)2]+. The low-spin ground state is calculated as (dxy2 (dπ)3 with dxy(dπ)4 higher by 0.15 eV. The near-ir bands at ~1 eV observed in low-spin ferriheme proteins are attributed to (π → dπ) transitions. The lowest high-spin state is 6A1g, and the near-ir transitions of the high-spin ferriheme proteins observed at ~1.2 eV are attributed to higher 6[tripsextet] excited states [i.e., ring triplet, metal sextet]. The 30-ps “triplet” transient populated with low quantum yield observed in laser-flash studies on FeIII(TPP)CI [TPP = tetrapbenylporphyrin] may be an 1[tripsextet] state. 相似文献
59.
Stará IG Alexandrová Z Teplý F Sehnal P Starý I Saman D Budesínský M Cvacka J 《Organic letters》2005,7(13):2547-2550
[reaction: see text] A new approach to nonracemic [7]helicene-like molecules has been developed. Stereoselective Co(I)-mediated [2 + 2 + 2] cycloisomerization of aromatic triynes containing an asymmetric carbon atom produces [7]helicene-like scaffolds in diastereomeric ratios up to 100:0. This central-to-helical chirality transfer can be controlled by the absolute configuration at the asymmetric center and by the presence of carbon substituents. 相似文献
60.
Ernest R. Davidson 《International journal of quantum chemistry》1974,8(1):83-89
It is shown that the turn-over rule which is used to simplify matrix elements between spin-projected Slater determinants may also be used to simplify formation of matrix elements between any orthonormal set of spin-coupled Slater determinants. The coefficients for the spin-coupling may then be chosen freely to reduce the number of important configurations in the secular equation. 相似文献