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排序方式: 共有829条查询结果,搜索用时 31 毫秒
1.
M Lepère R Gobeille V.Malathy Devi M.A.H Smith B Aoaeh A.W Mantz 《Journal of Molecular Spectroscopy》2004,224(1):7-12
We have analyzed the methyl fluoride RQ(J,0)Q branch lines located near 1475 cm−1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 RQ(J,0) lines. 相似文献
2.
Archana Devi 《European Polymer Journal》2007,43(6):2422-2432
Cardanol-based novolac-type phenolic resins were synthesized with different mole ratios of cardanol-to-formaldehyde, viz., 1:0.6, 1:0.7, and 1:0.8. These novolac resins were epoxidized with molar excess of epichlorohydrin at 120 °C in basic medium. The epoxidized novolac resins were, separately, blended with different weight ratios of carboxyl-terminated polybutadiene liquid rubber ranging between 0-25 wt% with an interval of 5 wt%. All the blends were cured at 150 °C with 40 wt% polyamide. The formation of various products during the curing of blend samples has been studied by Fourier-transform infra-red spectroscopic analysis. The tensile strength and elongation-at-break of the cured samples increased up to 15 wt% in the blend and decreased thereafter. This blend sample was also found to be most thermally stable system. The blend morphology, studied by scanning electron microscopy analysis, was finally correlated with the structural and property changes in the blends. 相似文献
3.
Protonation constant of an unsymmetrical Schiff base, salicylidene(N-benzoyl)glycyl hydrazone (SalBzGH), and formation constants
of its complexes have been determined potentiometrically at different temperatures in aqueous dioxane medium. Complexes of
SalBzGH with VO(IV), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) have been prepared. Elemental analyses, pH-metric,
molar conductance, magnetic susceptibility, electronic, IR, ESR, XRD (powder) and NMR studies have been carried out to study
the coordination behaviour of SalBzGH toward these metal ions. pH-metric and 1H NMR studies show the presence of two dissociable
protons in the ligand. IR and NMR spectra suggest the tridentate nature of the ligand, coordinating as a uninegative species
in the Mn(II) complex and as a dinegative species in all the other complexes. Presence of two different conformers of the
ligand at room temperature and stabilization of a single conformer upon complex formation have been established from1H NMR spectra of the metal-free ligand, Zn(II) and Hg(II) complexes recorded at 296 K. Electronic and ESR spectra indicate
highly distorted tetragonal geometry for VO(IV) and Cu(II) complexes. XRD powder patterns of the Zn(II) complexes are indexed
for an orthorhombic crystal system. 相似文献
4.
Navjeet Kaur Yamini Verma Pooja Grewal Neha Ahlawat Pranshu Bhardwaj Nirmala Kumari Jangid 《合成通讯》2020,50(9):1286-1334
AbstractFew conversions cannot take place with ground-state reactions even with the help of a catalyst, therefore they are made to occur under photochemical conditions. The transfer of electrons took place even with the photochemical excitement of one molecule where redox reaction cannot occur at the ground state. The ground-state reactions resulted in the formation of side products. The substrates did not require any sort of chemical activation for C–N bond construction in the course of photochemical reactions. The source of energy; light has always been the interest of researchers in order to induce chemical reactions ever since the starting of scientific chemistry. The present review encloses the chemistry of photochemical transformations with a focus on their synthetic uses. The organic photochemical reactions prevent the polluting or harmful reagents thus, provides a possibility for sustainable procedures as well as green chemistry. This review article displays the formation of numerous of five-membered fused nitrogen-heterocyclic compounds. 相似文献
5.
Collisions of I2 in the E electronic state with rare gas atoms result in electronic energy transfer to the D, beta, and D' ion-pair electronic states. Rate constants for each of these channels have been measured when I2 is initially prepared in the J = 55, nu = 1 and 2 levels in the E state. The rate constants and effective hard sphere collision cross sections confirm the trends observed when nu = 0 in the E state is initially prepared: He collisions favor population of the D state, while Ar collisions favor population of the beta state. Final state vibrational level distributions are determined by spectral simulation and are found to be qualitatively consistent with the trends in the Franck-Condon factors. The experimental distributions are also compared to the recent quantum scattering calculations of Tscherbul and Buchachenko. 相似文献
6.
Heat transfer in unsteady MHD channel flow (of an incompressible viscous and electrically conducting fluid) under oscillatory pressure gradient when the channel surfaces are conducting and moving with time-dependent velocities has been analysed. The velocity, magnetic field and temperature distributions have been obtained and their numerical results are shown graphically.Symbols
u
velocity
-
H
o
applied magnetic field
-
H
x
induced magnetic field
-
T
temperature
-
T
1
*
,T
2
*
temperatures of the upper and lower planes
-
density
-
p
pressure
-
kinematic viscosity
-
magnetic diffusivity
-
electrical conductivity of the fluid
-
A
*
characteristic velocity
-
L
characteristic length
-
e
magnetic permeability of the fluid
-
C
p
specific heat
-
coefficient of viscosity
-
k
thermal conductivity
-
1,
2
permeabilities of the planes
-
1,
2
conductivities of the planes
-
1,
2
conductance ratios of the planes
-
Pr
Prandtl number (=C
p
/k)
-
E
Eckert number
-
M
Hartmann number (=
e
H
o
L/)
-
R
e
Reynolds number (=LA
*/)
-
R
m
magnetic Reynolds number (=
e
LA
*)
-
S
Pr.E(=S) 相似文献
7.
Ipsita Devi 《Tetrahedron letters》2004,45(47):8625-8627
Sodium bromide catalysed three-component cyclocondensation of aryl aldehydes, alkyl nitriles and dimedone proceeds under microwave irradiation in solvent free conditions to give highly functionalised tetrahydrobenzo[b]pyrans in excellent yields. 相似文献
8.
Navjeet Kaur Neha Ahlawat Pranshu Bhardwaj Yamini Verma Pooja Grewal Nirmala Kumari Jangid 《合成通讯》2020,50(6):753-795
AbstractOne of the highly emerging and an important aspect of organic chemistry is the metal catalyzed synthesis of heterocycles. The methods used earlier for the synthesis of heterocycles were significant in the organic synthesis and developing cost-effective, improved and facial methods were beneficial to construct the complex architectures. For the both stereoselective and regioselective synthesis of six-membered nitrogen containing heterocycles, cyclic reactions that are Ag-mediated have known to be very efficient. The present review covers the applications of Ag in the formation of six-membered nitrogen containing heterocycles. 相似文献
9.
K. Ramulu B. M. Rao P. Madhavan M. Lalitha Devi M. K. Srinivasu K. B. Chandrasekhar 《Chromatographia》2007,65(3-4):249-252
A simple and new isocratic normal phase chiral HPLC method has been developed for the determination of enantiomeric purity
of pemetrexed disodium (l-enantiomer) in bulk drugs with a short run time of about 20 min. Chromatographic separation of l and d-enantiomers of pemetrexed disodium was achieved on an amylose based chiral stationary phase using a mobile phase consists
of hexane, ethanol and trifluoro acetic acid. The resolution between the enantiomers was found to be more than 2.0. The system
precision and method precision were found to be within 5% RSD for the distomer (d-enantiomer) at its specification level (i.e. not more than 1.0% w/w). The limit of detection and limit of quantification of distomer were 1.6 and 5 μg mL−1, respectively for 10 μL injection volume. The percentage recovery of distomer was ranged from 90.6 to 105.7 in bulk drug
samples. The test solution was found to be stable in the diluent for 48 h. The method was found to be specific for the enantiomers
of pemetrexed disodium and can be conveniently used for the quantification of undesired d-enantiomer present in the bulk drug samples of pemetrexed disodium. 相似文献
10.
Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported. 相似文献