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101.
Kinetics of the oxidation of methanol and mono-deutero-methanol by Cr(VI) over a wide range of temperature (25–40°) have been studied in perchloric acid medium at constant ionic strength (μ = 1.0 M) adjusted with sodium perchlorate. Each reaction is first order with respect to the substrate and dichromate concentrations but the order with respect to [H+] is nearly 3 in each case. Both these reactions take place at almost the same rate under identical experimental conditions. The activation parameters of the reactions are not widely different and the values of ΔH3 and ΔS3 for the oxidation of methanol are 79.5 kJ mole -1 and - 38.1 J deg-1 mole-1 respectively, whereas the corresponding values for the deuterated compound are 83.8 kJ mole-1 and -23.9 J deg-1 mole-1. The probable mechanism of the reactions is discussed. 相似文献
102.
The effect of radiation on the combined free and forced convection flow of an electrical conducting viscous fluid through an open-ended vertical channel in slip flow regime and permeated by a constant magnetic field in transverse direction has been considered. The temperature on the walls has been supposed to vary linearly with distance. On the assumption of optically thin limit, the expressions for velocity, induced magnetic field, temperature, flow rate and the heat transfer coefficient due to thermal conduction are obtained and the influence of radiation on these solutions are shown either graphically or in tabulated forms.Notation
x, y, z
cartesian coordinates
-
v
velocity
- 2L
distance between the channel walls
-
B
0
applied magnetic field
-
B
induced magnetic field
-
T
temperature
-
p
pressure
-
density
-
magnetic permeability
-
v
kinematic coefficient of viscosity
-
conductivity of the fluid
-
g
acceleration due to gravity
-
coefficient of volume expansion
-
thermal diffusivity of the fluid
-
c
p
specific heat at constant pressure
- qR
radiative heat flux
-
k
absorption coefficient
-
e
b
Plank function
-
T
0
reference temperature
-
N
vertical temperature gradient
-
M= B0L[/(v)]1/2
Hartmann number
-
R
a=gNL4/(v)
Rayleigh number
- Pm =
magnetic Prandtl number
- 2d1, 2d2
thickness of the walls
- 1, 2
conductivities of the walls 相似文献
103.
Blurring the Lines between Host and Guest: A Chimeric Receptor Derived from Cucurbituril and Triptycene 下载免费PDF全文
Dr. Xiaoyong Lu Dr. Soumen K. Samanta Dr. Peter Y. Zavalij Prof. Dr. Lyle Isaacs 《Angewandte Chemie (International ed. in English)》2018,57(27):8073-8078
We report the synthesis and X‐ray crystal structure of a cucurbituril–triptycene chimeric receptor ( 1 ). Host 1 binds to guests typical of CB[6]–CB[8], but also binds to larger guests such as blue box ( 20 ) and the Fujita square ( 22 ). Intriguingly, the geometries of the 1 ? 20 and 1 ? 22 complexes blur the lines between host and guest in that both components fulfill both roles within each complex. The fluorescence output of 1 is fully quenched by the formation of complexes with pyridinium‐derived guests. 相似文献
104.
Georgina M. Rosair Dilip Kumar Dey Brajagopal Samanta Samiran Mitra 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m266-m267
The structure of the title dimethyltin(IV) complex, [2‐(5‐bromo‐2‐oxidobenzylideneamino)benzoato‐κ3O,N,O′]dimethyltin(IV), [Sn(CH3)2(C14H8BrNO3)], features centrosymmetric dimers disposed about a central Sn2O2 core. Each Sn centre has seven‐coordinate pentagonal–bipyramidal geometry, taking into account two moderately long Sn—O contacts about an inversion centre [2.679 (4) and 2.981 (4) Å]. The methyl groups are in an axial orientation. 相似文献
105.
106.
Mandal SK Itkis ME Chi X Samanta S Lidsky D Reed RW Oakley RT Tham FS Haddon RC 《Journal of the American Chemical Society》2005,127(22):8185-8196
We report the preparation, crystallization, and solid-state characterization of the first members of a new family of spiro-bis-(1,9-diamino-substituted-phenalenyl)boron neutral radicals. The crystal structures show that the three radicals are monomeric and without close contacts in the crystal lattice. In all cases magnetic susceptibility measurements confirm the presence of free radicals with one unpaired spin per molecule. Two of the new radical compounds are among the most highly conducting neutral organic solids, with room-temperature conductivities reaching sigma(RT) = 4 x 10(-2) S/cm. The measured conductivities correlate with the closest intermolecular contacts in the solid state and with the calculated band dispersions, even though the bandwidths are much smaller than those found in other organic conductors. 相似文献
107.
Abbruzzetti S Grandi E Viappiani C Bologna S Campanini B Raboni S Bettati S Mozzarelli A 《Journal of the American Chemical Society》2005,127(2):626-635
We have used a nanosecond pH-jump technique, coupled with simultaneous transient absorption and fluorescence emission detection, to characterize the dynamics of the acid-induced spectral changes in the GFPmut2 chromophore. Disappearance of the absorbance at 488 nm and the green fluorescence emission occurs with a thermally activated, double exponential relaxation. To understand the source of the two transients we have introduced mutations in amino acid residues that interact with the chromophore (H148G, T203V, and E222Q). Results indicate that the faster transient is associated with proton binding from the solution, while the second process, smaller in amplitude, is attributed to structural rearrangement of the amino acids surrounding the chromophore. The protonation rate shows a 3-fold increase for the H148G mutant, demonstrating that His148 plays a key role in protecting the chromophore from the solvent. The deprotonation rate for T203V is an order of magnitude smaller, showing that the hydrogen bond with the hydroxyl of Thr203 is important in stabilizing the deprotonated form of the chromophore. A kinetic model suggests that, in addition to protecting the chromophore from the solvent, His148 may act as the primary acceptor for the protons on the way to the chromophore. 相似文献
108.
109.
C2-symmetric bisprolinamide as a highly efficient catalyst for direct aldol reaction 总被引:2,自引:0,他引:2
[reaction: see text] The catalytic activity of the prolinamide-type catalysts may be improved by introducing additional prolinamide moiety into the catalyst, while the enantioselectivity can still be maintained or further improved. A C2-symmetric bisprolinamide with two prolinamide moieties has been found to be an excellent catalyst for direct aldol reaction with more than doubled reactivity and better asymmetric induction than its monoprolinamide counterpart. 相似文献
110.
Five new fluorescent indicators for Ca2+ were synthesized using the Stille reaction. They all consist of the tricarboxylate chelator APTRA (o-aminophenol-N,N,O-triacetic acid) linked to a (substituted) bithiophene or terthiophene fluorophore. The dissociation constants Kd measured via fluorimetric titrations at 21 °C in 100 mM KCl buffered solution, pH 7.05, for the Ca2+ complexes with the new probes are in the range between 10 and 40 μM. 相似文献