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71.
An investigation of the conversion of Δ1-3,4-cis-THC 1a to Δ6-3,4-trans-THC 2a with BBr3 is described. By use of 1a of known optical purity it was determined that the main epimerization occurs at C-4. The small loss of optical purity observed during formation of 2a results from either competitive epimerization at C-3 or a racemization process. The conversion of 3,4-cis- to 3,4-trans-HHCs proceeds with exclusive C-4 inversion. 相似文献
72.
Cherenkov images are multifractal in nature. We show that multifractal behaviour of Cherenkov images arises due to multiplicative nature of pair production and bremsstrahlung processes in the longitudinal shower development passage. 相似文献
73.
LetG be a group,ZG the integral group ring ofG andI(G) its augmentation ideal. Subgroups determined by certain ideals ofZG contained inI(G) are identified. For example, whenG=HK, whereH, K are normal subgroups ofG andH∩K⊆ζ(H), then the subgroups ofG determined byI(G)I(H)I(G), andI
3(G)I(H) are obtained. The subgroups of any groupG with normal subgroupH determined by (i)I
2(G)I(H)+I(G)I(H)I(G)+I(H)I2(G), whenH′⊆[H,G,G] and (ii)I(G)I(H)I(G) when degH
2(G/H′, T)≤1, are computed. the subgroup ofG determined byI
n(G)+I(G)I(H) whenH is a normal subgroup ofG withG/H free Abelian is also obtained 相似文献
74.
Manindranath Bera Prasant Kumar Nanda Uday Mukhopadhyay Debashis Ray 《Journal of Chemical Sciences》2004,116(3):151-158
Low-temperature stoichiometric Schiff base reaction in air in 3:1 mole ratio between benzaldehyde and triethylenetetramine
(trien) in methanol yields a novel tetraaza μ-bis (bidentate) acyclic ligand L. It was characterized by elemental analysis, IR, EI mass and NMR (1H and13C) spectra. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging
unit gives rise to a new type of imidazolidine-bridged ligand. A geometric optimisation was made of the synthesized ligand
and its complexes by the method of molecular mechanics (MM2) method in order to establish the stable conformations. This hitherto
unknown tetraaza acyclic ligand affords new cationic dicopper(I/I) and dicopper(II/II) complexes in good yield. Dicopper(II/II)
complex displays weakd-d transition bands in the visible region, while dicopper(I/I) complex displays strong MLCT band in the same region. Both the
dinuclear complexes are of non-intimate nature and show interesting solution electrochemical behaviour. EPR spectral study
of μ-bis (imidazolidino) bridged dicopper(II/II) complex also supports the non-communicative nature of the two copper centres within
the same molecule 相似文献
75.
[structure: see text] A novel cholaphane has been synthesized from a naturally occurring bile acid in just two steps. It has an ability to bind two fluoride ions selectively utilizing the glycolate motif in chloroform. This "inside-out" cyclodextrin analogue encapsulates fluoride through O-H...F(-) and C-H...F(-) interaction. 相似文献
76.
Synthesis of nanostructure hydrous iron–titanium binary mixed oxide (NHITBMO) had been reported by a simple method, and characterized by the X-ray diffraction (XRD), thermal analysis, transmission electron microscope (TEM), Föurier Transform Infrared (FTIR), surface area, and zero surface charge pH (pHzpc). The synthetic oxide was hydrated and microcrystalline with 77.8 m2 g?1 BET surface area. The particle size (nm) calculated using XRD peak table and TEM image was ~10–13 and 6–8, respectively. The pHzpc value was 6.0 (±0.05) for the oxide. The NHITBMO showed pH dependent good sorption affinity for arsenic from the aqueous solution and, the Langmuir monolayer capacity (mg g?1) was 80.0 and 14.6, respectively, for the As(III) and As(V). The pseudo-second order equation described the room temperature arsenic sorption kinetic data well. The minimum dose required was 1.6 g NHITBMO per L of water (Astotal = 0.24 mg L?1) to reduce the arsenic level below 0.01 mg L?1 in batch treatment process. 相似文献
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80.
Several nonlinear systems such as the Korteweg-de Vries (KdV) and modified KdV equations and lambda phi(4) theory possess periodic traveling wave solutions involving Jacobi elliptic functions. We show that suitable linear combinations of these known periodic solutions yield many additional solutions with different periods and velocities. This linear superposition procedure works by virtue of some remarkable new identities involving elliptic functions. 相似文献