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991.
992.
《Electroanalysis》2003,15(4):249-253
Cyclic voltammetric measurements were made using well‐characterized microcrystalline boron‐doped diamond thin‐film electrodes to test the material's responsiveness for ferrocene as a function of scan rate, solvent, and electrolyte composition. Apparent heterogeneous electron transfer rate constants, k°app, of 0.042±0.015, 0.048±0.015, and 0.008±0.002 cm/s were observed in 0.1 M NaClO4/CH3CN, 0.1 M TBAClO4/CH3CN, and 0.1M TBAClO4/CH2Cl2, respectively. These rate constants, obtained using electrodes without any type of pretreatment, are similar to those observed for freshly polished glassy carbon. The results demonstrate that boron‐doped diamond is a viable material for the electrochemical analysis of nonaqueous analytes. 相似文献
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997.
S. Vandervelde 《Journal of Number Theory》2003,100(1):184-202
We introduce a formula for the Mahler measure of axy+bx+cy+d with complex coefficients a,b,c, and d and give examples which demonstrate a connection with L-functions. We then prove a generalization of Maillot's formula when the coefficients are real. Next, we discuss operations on the coefficients which fix the Mahler measure. Finally, we prove an alternate formulation of the main result in order to calculate the Mahler measure of a two-parameter family of polynomials in three variables. 相似文献
998.
Christopher J. Arnusch 《Tetrahedron letters》2004,45(21):4153-4156
The synthesis and NMR analysis of a novel highly constrained scaffold is described. The 14-membered macrocyclic ring structure was inspired by many medicinally relevant natural products that also contain the bi-aryl ether moiety. The synthesis required only commercially available starting materials and involved a base mediated SNAr cyclization. A conformational search was performed, which indicated a strong preference for a single conformation, which was consistent with observed ROE signals by NMR. 相似文献
999.
1,4-Diarylimidazoline 3-oxides react with N-arylmaleimides in benzene to give predominantly the corresponding endo adducts. Chiral imidazoline 3-oxides react diastereospecifically (cis configuration of the tetrahydroimidazo ring) and diastereoselectively to give cis-endo adducts. The effects of substituents on the aromatic ring of the maleimide was investigated. The presence of electron-withdrawing or releasing groups have minor effect on the total yields but more pronounced is the effect on the ratio of exo and endo diastereomers. The adducts undergo an interesting and unprecedented ring-opening in the presence of secondary amines to give deoxygenated 3-imidazoline 3-oxides instead of the expected double cis elimination products. Tertiary amines did not induce any reaction. 相似文献
1000.
Hyun Sook Kim Yu-Mi Song Jin Seok Choi Jung Woon Yang Hogyu Han 《Tetrahedron》2004,60(52):12051-12057
The silica gel-supported bis-cinchona alkaloid 1a was prepared and found to be an efficient heterogeneous chiral organocatalyst with high catalytic activities, enantioselectivities (up to 92% ee), and recyclability for the asymmetric desymmetrization of meso-cyclic anhydrides with alcoholysis. 相似文献