共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
3.
Z. V. Todres E. A. Ionina V. A. Nikanorov S. V. Sergeev 《Russian Chemical Bulletin》1992,41(1):174-176
A study was carried out on the interactions of the Z and E forms of the indicated stilbenes in all four possible combinations. Charge transfer complexes are formed and only Z-p,p-dimethoxystilbene converts to its E form.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 210–211, January, 1992. 相似文献
4.
Hussen A Westbom R Megersa N Retta N Mathiasson L Björklund E 《Analytical and bioanalytical chemistry》2006,386(5):1525-1533
The effectiveness of extracting p,p′-DDT and p,p′-DDE from aged contaminated soil samples by means of pressurized liquid extraction (PLE) was evaluated. Two soil samples,
which were contaminated more than 10 years ago, were used in the investigation. The static extraction time was optimised and
then validated against the total sum of target analytes obtained from multiple sequential extractions. The PLE results were
also compared with Soxhlet extraction (SOX). PLE for 3×10 min at 100 °C was proven to be more exhaustive than SOX in the
determination of p,p′-DDE from both soil samples. In the case of p,p′-DDT, PLE was found to be equally as exhaustive as SOX. Additionally, most of the previous PLE investigations used hazardous
organic solvents such as n-hexane, toluene and dichloromethane mixed with acetone, whereas in this investigation the less toxic solvent combination
n-heptane/acetone has been employed. 相似文献
5.
p,p′-Phenolphthalein-bis(trimellitic) dianhydride was obtained by the reaction of diacetyloxyphenolphthalein with trimellitic anhydride. The structure of the new compound was proved by elementary analysis, infrared spectroscopy, and acid value determination. The course of acidolysis reaction was examined in the temperature range of 240–280°C. The compound obtained is a powder having a melting point of 135–138° C, has high thermal stability, and is easily soluble in many organic solvents and low-molecular epoxy resins. Application of p,p′-phenolphthalein-bis(trimellitic) dianhydride in synthesis of soluble polyester-imides and as a hardening agent for low molecular weight epoxy resins is proposed. 相似文献
6.
7.
Aránzazu Martínez-Gómez Ernesto Pérez Antonio Bello 《Colloid and polymer science》2010,288(8):859-867
The phase transitions and the orientational behavior of liquid crystalline poly(triethylene glycol p,p′-bibenzoate) have been studied. The real-time synchrotron diffraction results indicate that, on cooling from the isotropic
melt, an orthogonal SmA mesophase is formed first, and later it is transformed into a tilted SmC mesophase. However, the SmA
mesophase is stable in a rather wide temperature interval, and the transformation into the SmC phase occurs at temperatures
close to the glass transition, so that not very high tilting angles are attained. The uniaxial deformation of the SmC mesophase
indicates that usual parallel orientation of the molecular axes in relation to the stretching direction is obtained at high
strain rates, while anomalous perpendicular orientation occurs at low deformation rates, with the smectic layers aligned with
the stretching direction and the molecular axes almost perpendicular. A mixture of the two types of orientation is observed
at intermediate rates, with rather interesting features. 相似文献
8.
In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p’-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy. 相似文献
9.
Hardening of a low molecular epoxy resin with p,p′-phenol-phthalein-bis(trimellitic) dianhydride has been studied by using differential scanning calorimetry. The relationships of glass transition temperature of the systems being examined versus time, temperature of hardening, and dianhydride content in the compositions have been determined. The activation energy of crosslinking reactions in systems containing 50% of the stoichiometric amount of dianhydride has been evaluated. The value of activation energy obtained indicates a high reactivity of dianhydride in the examined reactions. The hardened epoxy composition exhibits excellent thermal stability, good hardness, and good resistance to acid solutions. During research on soluble, regularly alternating polyesterimides, a synthesis of p,p′-phenolphthalein-bis(trimellitic) dianhydride was carried out and thus a new compound obtained [1]. The presence in the molecule of this new compound of four functional groups capable of reacting with epoxy groups and good solubility in organic solvents and low molecular epoxy resins suggested the use of this compound as a hardening agent for liquid resins. Examinations of the hardening process were conducted by using a low molecular epoxy resin (Beckopox 37–140) which is equivalent to Epidiane 5 and Epikotc 828. 相似文献
10.
B. Glöckner 《Monatshefte für Chemie / Chemical Monthly》1949,80(4):489-492
Ohne ZusammenfassungMit 1 Abbildung 相似文献
11.
pppA2′p5′A2′p5′A(2′-5′P_3A_3)受体可能是第一个寡核苷酸受体。但ATP能与2′-5′P_3A_3竞争此受体,那么ATP的作用是什么呢?本文证明ATP虽然对巨噬细胞的结合具有饱和性和可逆性,似乎是2′-5′P_3A_3受体的一个配基,但ATP并不能提高巨噬细胞的吞噬功能,而且当ATP和2′-5′P_3A_3同时作用于巨噬细胞时,ATP反而抑制2′-5′P_3A_3~′对巨噬细胞的生物效应。如果ATP先与巨噬细胞作用占据了2′-5′P_3A_3所要结合的位点后,再加2′-5′P_3A_3时,则2′-5′P_3A_3的结合能力和引起的生物学效应都明显地被阻断了,这表明,2′-5′P_3A_3的作用是通过它的受体而发挥的,ATP则可能是2′-5′P_3A_3受体的一个拮抗剂。 相似文献
12.
13.
《Analytical letters》2012,45(14):2365-2375
Abstract A sensitive and selective spectrophotometric method is proposed for the rapid determination of cadmium(II) using, p,p′‐dinitro‐sym‐diphenylcarbazid, directly in aqueous solution. The reaction between cadmium(II) and p,p′‐dinitro‐sym‐diphenylcarbazid occurs immediately in strong basic media (0.02 N sodium hydroxide solution). The complex shows a maximum of absorption at 630–640 nm, and the absorbance remains stable for at least 24 h. The method allows the cadmium determination over the range 0.5–6.0 µg mL?1, with a molar absortivity of 2.05×104 L mol?1 cm?1 and features a detection limit of 0.13 ppm. The interferences caused by several ions [Ca(II), K(I), Ba(II), Al(III), Pb(II), Zn(II), Cl?1, NO3 ?, SO4 2?], which are present in most of environmental samples, were determined. The validation of the spectrophotometric method was done by recovery test of cadmium(II) in tap water and sea water. The results show that the proposed method has been successfully applied to the determination of cadmium(II) in water samples. 相似文献
14.
15.
5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines. 相似文献
16.
The chlorination of N-alkoxy-N-alkylureas (1) by the action oft-BuOCl proceeds regiospecifically to give stable N-chloro-N-alkoxy-N-alkylureas (2). The alcoholysis of2 leads to N,N-dialkoxy-N-alkylureas (3). The alkaline hydrolysis of3 is a new, convenient method for the preparation of dialkoxyamines.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2441–2443, October, 1992. 相似文献
17.
Ohne Zusammenfassung 相似文献
18.
The step dissociation constants of ethylenediamine-N,N′-diacetic-N,N′-dipropionic and ethylenediamine-N,N,N′,N′-tetrapropionic acids at 298.15 K and ionic strengths of 0.1, 0.5, and 1.0 (KNO3) were determined potentiometrically. The results were extrapolated to zero ionic strength by the equation with one individual parameter. The thermodynamic constants of dissociation were calculated. The results are compared with the corresponding data on related compounds. 相似文献
19.
A convenient and high yield preparation of 4, 4′-dicarboxy-2, 2′-bipyridine from the oxidation 4, 4′-dimethyl-2, 2′-bipyridine with potassium dichromate in sulfuric acid is reported. 相似文献
20.
A fluorinated tetraphenylbenzidine derivative, N,N′-diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine (C36H26F2N2, Mr = 524.59) was synthesized via the palladiumcatalyzed Buchwald-Hartwig reaction of N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine with 2-fluoroiodobenzene (yield: 75%) and structurally characterized. It crystallizes in monoclinic, space group P21/n with a = 9.820(7), b = 14.305(11), c = 10.233(8) , β = 108.973(9)o, V = 1359.3(18) 3, Z = 2, Dc = 1.282 g/cm3, μ(MoKα) = 0.084 mm-1, F(000) = 548, S = 1.018, the final R = 0.0439 and wR = 0.0928. It presents a linear centrosymmetric framework constituted by a linkage of biphenyl as a bridge and two fluorinated diphenylamine moieties. The UV-Vis absorption and fluorescence spectra of the title compound were also investigated. This compound emits intense blue fluorescence with a peak wavelength of 406 nm in film. 相似文献