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51.
Alcohol ethoxylates (AEs) are nonionic surfactants. They are industrially important compounds that have historically been difficult to analyze, with the best results to date achieved through derivatization (e.g., silylation) followed by analysis by gas chromatography/mass spectrometry (GC/MS). Recently, mass spectrometric techniques such as field desorption (FD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) have been employed to analyze surfynol(R) 4xx. In an effort to produce low-cost alkyl-capped AEs and anionic detergents from AEs, a fast and reliable measure of the product yields and conversions from AEs is required in research. We found that the product yields and conversions from reactions of AEs, obtained by the employment of atmospheric pressure chemical ionization (APCI), were in good agreement with those obtained from proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Therefore, APCI can be used as a validated tool for studying AE reactions. Mixtures that contain either silylated or unsilylated ethoxylates and/or carboxylates yield the same APCI mass spectra. Copyright -Copyright 1999 John Wiley & Sons, Ltd. 相似文献
52.
Ki Hwan Bae 《中国化学快报》2009,20(11):1321-1323
Phytochemical study on the BuOH-soluble fraction of the stem bark of Populus davidiana resulted in the isolation of a new salicin derivative(1),named davidianoside.The structure was elucidated on the basis of extensive physicochemical and spectroscopic analyses. 相似文献
53.
S Rayaprol Krushna Mavani CM Thaker DS Rana Keka Chakravorty SK Paranjape M Ramanadham Nilesh A Kulkarni DG Kuberkar 《Pramana》2002,58(5-6):877-880
A new series of mixed oxide superconductors with the stoichiometric composition La2−x
Dy
x
Ca
y
Ba2Cu4+y
O
z
(x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x
(Y/Er)
x
Ca
y
Ba2Cu4+y
O
z
series, show a strong dependence of T
c on hole concentration (p
sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant
displacement of La onto Ba site. Superconductivity studies show that maximum T
c is obtained for x=0.5, y=1.0 sample (T
c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O
z
(La-2125). 相似文献
54.
The Setschenow parameter and thermodynamic parameters of transfer of 2-, 3- and 4-fluorobenzoic acid from water to salt solution are reported. The data have been rationalized by considering the structure breaking effects of the ions of the salts, the localized hydrolysis model and the internal pressure theory. 相似文献
55.
Rahna Koyakutty Shamsudeen Kanat Nisha Sankaran Sugunan 《Reaction Kinetics and Catalysis Letters》2004,81(2):341-348
Vanadia impregnated iron-pillared montmorillonites with different weight percentages of vanadia have been prepared. Subsequent
characterization by XRD, FT-IR, surface area and pore volume measurements was carried out. Acidity was determined by three
independent techniques namely thermogravimetric desorption of 2,6-dimethylpyridine, spectrophotometric monitoring of adsorption
of perylene and temperature-programmed desorption of ammonia. Conversion of cumene in the vapor phase has been performed as
a test reaction of acidity. Aniline methylation was carried out to check the catalytic efficiency of the solids.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
The limit of electron transfer in electron affinity from the oxide surface to the electron acceptor (EA) are reported from the adsorption of EA on Dy2O3, mixed oxides of Dy2O3 with alumina and mixed oxides of Y2O3 with -alumina. The extent of electron transfer is understood from magnetic measurements. 相似文献
57.
Acidity/basicity of mixed oxides of ZrO2−Y2O3 activated at various temperatures were determined by a titration method using Hammett indicators. The activity of these oxides
towards liquid phase oxidation of cyclohexanol are also reported. The activity data parallel the basicity of these oxides. 相似文献
58.
Aspherical‐Atom Modeling of Coordination Compounds by Single‐Crystal X‐ray Diffraction Allows the Correct Metal Atom To Be Identified
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Dr. Birger Dittrich Claudia M. Wandtke Dr. Alke Meents Dr. Kartik Chandra Mondal Dr. Prinson P. Samuel Nurul Amin SK Dr. Amit Pratap Singh Prof. Dr. Herbert W. Roesky Dr. Navdeep Sidhu 《Chemphyschem》2015,16(2):412-419
Single‐crystal X‐ray diffraction (XRD) is often considered the gold standard in analytical chemistry, as it allows element identification as well as determination of atom connectivity and the solid‐state structure of completely unknown samples. Element assignment is based on the number of electrons of an atom, so that a distinction of neighboring heavier elements in the periodic table by XRD is often difficult. A computationally efficient procedure for aspherical‐atom least‐squares refinement of conventional diffraction data of organometallic compounds is proposed. The iterative procedure is conceptually similar to Hirshfeld‐atom refinement (Acta Crystallogr. Sect. A 2008 , 64, 383–393; IUCrJ. 2014 , 1,61–79), but it relies on tabulated invariom scattering factors (Acta Crystallogr. Sect. B 2013 , 69, 91–104) and the Hansen/Coppens multipole model; disordered structures can be handled as well. Five linear‐coordinate 3d metal complexes, for which the wrong element is found if standard independent‐atom model scattering factors are relied upon, are studied, and it is shown that only aspherical‐atom scattering factors allow a reliable assignment. The influence of anomalous dispersion in identifying the correct element is investigated and discussed. 相似文献
59.
S. Sugunan D. John N. K. Renuka M. Varghese K. Sreekumar C. G. Ramankutty 《Reaction Kinetics and Catalysis Letters》1999,66(1):39-45
The electron donating properties of manganese ferrospinels of various compositions (MnFe2O4, Mn1.2Fe1.8O4, Mn2FeO4 and Mn2.5Fe0.5O4) were studied from the adsorption of electron acceptors of various electron affinity values from acetonitrile as solvent.
The limit of electron transfer from the oxide surface is from 1.77 to 2.40 eV in terms of the electron affinity of the electron
acceptor. The data have been correlated with the catalytic activity of these oxides towards autoxidation of sulfites. Both
weak and strong electron donor sites catalyze the reaction. 相似文献
60.
Alkylation of Phenol with Methanol Over Rare Earth Promoted Sulfated Tin Oxide Catalyst 总被引:2,自引:0,他引:2
T.M. Jyothi K. Sreekumar B.S. Rao S. Sugunan 《Reaction Kinetics and Catalysis Letters》2000,69(2):339-343
A comparative account of the tin-samarium binary oxide and its sulfate modified analogue (SO4
2- / SnO2-Sm2O3) in the alkylation of phenol with methanol is reported. Sulfate modification resulted in a large variation in product selectivity and reaction pathway due to the creation of strong acid sites, which alters the nature of adsorption of phenol on the catalyst surface. 相似文献