排序方式: 共有31条查询结果,搜索用时 15 毫秒
1.
The MP2 method in combination with the aug-cc-pVXZ (X = D and T) basis set has been carried out to examine the complexes between O3 and isostructure species of CO2, CS2 and SCO. Two, two and four minima have been located on the potential energy surfaces of O3–CO2, O3–CS2 and O3–SCO complexes, respectively. The results reveal that the stabilization of complexes should be in the order O3–CS2 > O3–SCO > O3–CO2. 相似文献
2.
3.
Moein B. Sayed 《Journal of Solid State Electrochemistry》2003,7(4):223-231
Variable strength H-bonding affects the mobility and so electric conduction of protons differently. Also, variable extent
mesomerism modifies electric conduction with varying dielectric features. Both these molecular modifiers are properly cited
using azophenol derivatives as model compounds for discussion of their consequences in the varying features of electric conduction.
The electric permittivity shows low-frequency dispersion characteristic of ionic conduction over mobile charge carries; the
mobility shifts at a critical temperature T
c, being structure dependent. The frequency-dependent Z′′-Z′ layout changes with temperature from linear at low temperatures to semicircular above T
c within a frame of temperature-sensitive dipole-ionic mediated conduction. The a.c. conductivity, σac, increases with frequency and temperature and becomes frequency insensitive, like d.c. conductivity, σdc, above the T
c because of the escalating contribution from the d.c. conduction. The mesomeric structure seems to prompt a dipole-based electric
conduction of high relaxation energy over the strongly associated phenolic protons that may be thermally activated above the
T
c into a much lower relaxation energy protonic conduction of up to two orders higher conductivity. The protonic conduction
emerges at a T
c that falls with a drop in the relaxation energy following a similar order of increasing proton mobility and mesomerism in
the azophenol derivatives: azocatechol>azoquinol>azoresorcinol. On the molecular level, variable temperature infrared spectroscopy
reveals higher proton mobility and mesomerism for the azocatechol derivative that demonstrates its higher protonic conductivity
at lower T
c and relaxation energy, compared to the azoquinol and azoresorcinol derivatives. This is well verified in the light of conflicting
intramolecular H-bonding that assists the proton mobility in azocatechol whereas it associates the protons in azoresorcinol
more than in azoquinol.
Electronic Publication 相似文献
4.
Eckhard Herrmann Moein Nouaman Zdirad
k Gisbert Großmann Gisela Ohms 《无机化学与普通化学杂志》1994,620(11):1879-1888
Tetraarylesters of μ-Imido-Diphosphoric Acid and its Thio Derivatives — Structure Investigations New O,O′,O″,O?-tetratolyl- and ditolyl-diphenylesters of the μ-imido-diphosphoric acid and its mono and dithio derivatives were synthesized, compared with the corresponding tetraphenylesters and investigated by 1H, 13C, and 31P NMR spectroscopy and X-ray crystal structure analysis. Structures of the O,O′,O″,O?-tetrakis-(2-methyl-phenyl)-μ-imidodiphosphate, 1b , as well as of the corresponding ortho-, meta- and para-tolylesters of the μ-imido-monothiodiphosphoric acid ( 2a , 2b , 2c ) were determined. All the compounds form dimers via N? H…?O hydrogen bonds in the crystal as well as in nonpolar solvents. The distances around the phosphorus atoms rise with decreasing electronegativity of the phosphorus substituents. Signs of the 2JP? N? P coupling constants were determined by 13C{1H, 31P} triple resonance experiments for some compounds. These constants become more negative owing to substitution of a phosphoryl by a thiophosphoryl group. 相似文献
5.
The mean centering of ratio kinetic profiles method was used for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) in water samples, without prior separation steps. The method is based on the difference in the rate of the reaction of Ni(II) and Zn(II) with xylenol orange at pH 5.3. The method allows rapid and accurate determination of Ni(II) and Zn(II). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) were calculated. The linear range was 0.025‐2.400 μg mL?1 and 0.025‐2.20 μg mL?1 for Zn(II) and Ni(II), respectively. Interference effects of common anions and cations were studied, and the method was successfully applied to the simultaneous determination of Zn(II) and Ni(II) in water samples. 相似文献
6.
Dynamic response systems are often found in science, engineering, and medical applications, but the discussion on experimental design for such a system is relatively rare in literature. For an experimenter, designing such experiments requires making decisions on (1) when or where to take response measurements along the dynamic variable and (2) how to choose the combination of experimental factors and their levels. The first consideration is unique for such experiments, especially when the measurement cost is high. In this paper, we present a design approach through the mixed‐effect linear model, which is based on a hierarchical B‐spline function for the dynamic response. We develop several theorems that can assist in finding a statistically efficient sampling plan and propose an algorithm for searching the D‐optimal design of a dynamic response system. 相似文献
7.
Structural Chemistry - The reaction mechanism of disulfur (S2) and O3 on the triplet and singlet potential energy surfaces has been investigated theoretically at the... 相似文献
8.
An Efficient One‐pot Access to Substituted Dihydropyrrol‐2‐one Derivatives Using Sucrose as Natural,Biodegradable and Inexpensive Catalyst 下载免费PDF全文
Nourallah Hazeri Seyed Sajad Sajadikhah Malek Taher Maghsoodlou Sajad Mohamadian‐Souri Mahmoud Norouzi Maryam Moein 《中国化学会会志》2014,61(2):217-220
An efficient and simple procedure for the synthesis of highly substituted dihydropyrrol‐2‐ones has been developed via one‐pot four‐component condensation of amines, dialkyl acetylenedicarboxyaltes and formaldehyde in the presence of sucrose as an organocatalyst. The salient advantages of this method are using a natural, biodegradable and commercial available catalyst, good yields, short reaction times, simple work‐up and lack of need for column chromatography. 相似文献
9.
A series of new polycalixesters(PCES) were synthesized by polyesterification of calixarene dicarboxylic acid derivatives having tertiary butyl pendant groups at the upper rim using five different diols. All polyesters were readily soluble in polar solvents such as NMP(N-methylpyrrolidone), DMF(dimethylformamide), DMSO(dimethylsulfoxide), pyridine, THF(tetrahydrofurane), HMPA(hexamethylenephosphoramide) and DMAC(dimethylacetamide). The PCES were also partially soluble in TCE(tetrachloroethane) and ethanol and they were unsoluble in aceton. The glass transition temperatures of polyesters were between 80-184 °C, the crystallinity temperatures of polyesters were between 130–212 °C and the melting temperatures of polyesters were between 185–234 °C, as determined by differential scanning calorimeter(DSC). The inherent viscosities of polyesters were obtained from 0.55 dL/mg to 0.61 dL/mg. The temperatures at 10% weight loss of polyesters ranged from 182 °C to 237 °C. The temperatures at 25% weight loss of polyesters ranged from 258 °C to 331 °C. The half weight loss(50%) temperatures of polyesters were among 315 °C to 371 °C and the char yields at 600 °C were determined within 13% to 22.3% in N2 atmosphere, as determined by thermo gravimetric analysis(TGA). The polyester, PES3, has the higher melting point(234 °C) and higher inherent viscosity(molecular weight) than the other polyesters. 相似文献
10.