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51.
By employing the chelation strategy, treatment of an acetal of a contiguous diol with Me3SiCH2MgCl liberates the corresponding diol regioselectively. In addition, acetals of different structural variety are transformed upon treatment with Me3SiCH2MgCl and ZnI2 into the corresponding olefination products in good yield. 相似文献
52.
Summary An efficient procedure for the synthesis of the potassium salts of (4-morpholino)acetic acid, HL, and its -substituted derivatives is described. The title complex has been prepared and characterized by x-ray crystallography:a=8.505(2),b= 7.901(1),c=12.253(2) Å, =110.48(1)°, space groupP21/c,Z = 2, RF=0.038 for 2300 observed MoK data. Hydrogen bonds link the centrosymmetrictrans-octahedral bis-chelated CuL2(H2O)2 moieties into layers parallel to (100) in the crystal lattice. 相似文献
53.
Let p={pv} be a fixed sequence of complex numbers. Define \(p_n : = \mathop \Sigma \limits_{\nu = o}^n p_\nu \) and suppose that \(p_{m_k } \ne o\) for a subsequence M={mk} of nonnegative integers. The matrix A=(αkv) with the elements $$\alpha _{k\nu } = p_\nu /p_{m_k } if o \leqslant \nu \leqslant m_k ,\alpha _{k\nu } = oif \nu > m_k $$ generates a summability method (R,p,M) which is a refinement of the well known Riesz methods. The (R,p,M) methods have been introduced in [4]. In the present paper we are concerned with the summability of the geometric series \(\mathop \Sigma \limits_{\nu = o}^n z^\nu \) by (R,p,M) methods. We prove the following theorem. Suppose G is a simply connected domain with \(\{ z:|z|< 1\} \subset G,1 \varepsilon | G \) . Then there exists a universal, regular (R,p,M) method having the following properties: (1) \(\mathop \Sigma \limits_{\nu = o}^\infty z^\nu \) is compactly summable (R,p,M) to \(\tfrac{1}{{1 - z}}\) on G. (2) For every compact set B?¯Gc which has a connected complement and for every function f which is continuous on B and analytic in its interior there exists a subsequence M(B,f) of M such that \(\mathop \Sigma \limits_{\nu = o}^\infty z^\nu \) is uniformly summable (R,p,M(B,f)) to f(z) on B. (3) For every open set U?Gc which has simply connected components in ? and for every function f which is analytic on U there exists a subsequence M(U,f) of M such that \(\mathop \Sigma \limits_{\nu = o}^\infty z^\nu \) is compactly summable (R,p,M(U,f)) to f(z) on U. 相似文献
54.
Wei‐Yu Lin Hsian‐Wen Wang Zhi‐Chang Liu Jun Xu Chih‐Wei Chen Yun‐Chin Yang Shou‐Ling Huang Hsiao‐Ching Yang Prof. Tien‐Yau Luh Prof. 《化学:亚洲杂志》2007,2(6):764-774
Two dimers and a series of polymers with 5,6‐endo pendant aryl groups that contain different substituents at the para positions were synthesized. The conformation and stereochemistry of the dimers and polymers were determined by nonlinear optical analysis (EFISH) as well as UV/Vis and 13C NMR spectroscopy. The chemical shifts of C7 for the polymers appeared as two peaks in the 13C NMR spectra when the substituents are electron‐withdrawing groups. The percentage decrease in the relative extinction coefficient of the polymers, εd, was linearly related to the Hammett constant σ. Polynorbornenes with electron‐withdrawing substituents may adopt isotactic stereochemistry with all pendant groups aligned in one direction. The nature of the interactions between neighboring chromophores may be one of the most important factors in directing the stereoregularity and conformation of these polymers. The corresponding polymers derived from the exo isomers appeared to be less stereoregular. 相似文献
55.
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57.
Lin WY Murugesh MG Sudhakar S Yang HC Tai HC Chang CS Liu YH Wang Y Chen IW Chen CH Luh TY 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,12(1):324-330
A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure. 相似文献
58.
Let G ⊂ C be a domain which is bounded by a finite number of pairwise disjoint Jordan curves. We prove the existence of a function
which is holomorphic exactly on G and has universal translates with respect to a prescribed set E ⊂∂G and which in addition is continuous on G
-\E.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
59.
J. L. Zakin R. Wu H. Luh K. G. Mayhan 《Journal of Polymer Science.Polymer Physics》1976,14(2):299-308
Data are presented to show that two correlations of viscosity–concentration data are useful representations for data over wide ranges of molecular weight and up to at least moderately high concentrations for both good and fair solvents. Low molecular weight polymer solutions (below the critical entanglement molecular weight Mc) generally have higher viscosities than predicted by the correlations. One correlation is ηsp/c[η] versus k′[η], where ηsp is specific viscosity, c is polymer concentration, [η] is intrinsic viscosity, and k′ is the Huggins constant. A standard curve for good solvent systems has been defined up to k′[η]c ≈? 3. It can also be used for fair solvents up to k′[η]c ≈? 1.25· low estimates are obtained at higher values. A simpler and more useful correlation is ηR versus c[η], where ηR is relative viscosity. Fair solvent viscosities can be predicted from the good solvent curve up to c[η] ≈? 3, above which estimates are low. Poor solvent data can also be correlated as ηR versus c[η] for molecular weights below 1 to 2 × 105. 相似文献
60.