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61.
New chlorophosphonates bearing a 1,3,2-dioxaphosphorinane ring which are useful for the stereospecific synthesis of 5-chlorofurfuryl substituted olefins and chloro-substituted dienes have been obtained by an easy, inexpensive route. The utility of some of these in the synthesis of ferrocenyl- and anthracenyl-substituted unsymmetrical acetylenes has been explored. The structures of the phosphonates (OCH(2)CMe(2)CH(2)O)P(O)CH(2)(C(4)H(2)ClO) (4) and (OCH(2)CMe(2)CH(2)O)P(O)(CH=CHCH(Cl)Ph (7) have been determined; in addition, the stereochemistry of (5-chlorofurfuryl)CH=CH(4-ClC(6)H(4)) (13b) and 2, 4-Cl(2)C(6)H(3)-CH=CH-CH=C(Ph)Cl (14a) is unambiguously proved by the X-ray structure determination. 相似文献
62.
In the present report, we have done specific heat measurements in glassy Se80?xTe20Sbx (0 ≤ x ≤ 15) alloys in glass transition region. Differential scanning calorimetry (DSC) technique is used for this purpose. We have observed a tremendously huge increase in the specific heat (Cp) values at the glass transition temperature. The thermal analysis shows that the values of Cp below glass transition temperature and the difference of Cp values before and after glass transition (?Cp) are highly composition-dependent. 相似文献
63.
Mixtures of calcium oxide (taken as carbonate) and silica in 2:1 molar ratio containing varying amounts of MgO, SrCO3 and BaCO3 as dopants were subjected to thermal treatment up to 1450°C. The exothermic peaks at 1200°C and above (beyond the decomposition temperature of calcium carbonate) have been examined to elucidate the phases formed. The exothermic peak at 1210°C without dopant was found to conform to the β-dicalcium silicate phase with a significant amount of free lime and cristobalite along with small amounts of the γ-C2S phase. MgO at 0.1–1% leads to the formation of β- and γ-dicalcium silicate phases at 1420–1430°C, while 5% MgO results in the formation of the β-C2 S phase at 1360°C. SrCO3, in the concentration range studied, leads to the stabilization of β-C2S, but does not lower its temperature of formation. BaCO3 at 0.1–1% assists in the formation of the β-dicalcium silicate phase, but 5% BaO forms a mixture of β- and α'H-C2S phases at a lower temperature. 相似文献
64.
Christophe Bénard Rahim Mohammad Neerja Saraswat Rudong Shan Samarendra N. Maiti Peter G. M. Wuts 《合成通讯》2013,43(4):517-524
Chiral 3‐methanesulfonyl‐1‐Boc‐pyrrolidine and piperidine were reacted with sodium phenolates, resulting in a mixture of displacement and elimination products. Following carbamate deprotection and pH adjustment, the 3‐pyrroline and tetrahydropyridine by‐products resulting from elimination were easily removed through aqueous partitioning and/or concentration. Although the pyrrolidines were formed with a high degree of optical purity, slight racemization was observed for the piperidine case because elevated temperatures were required to effect displacement. 相似文献
65.
The Meyer–Neldel rule or MN rule (also known as compensation effect) is an empirical law known since 1937. This rule is observed in wide range of phenomena in physics, chemistry, biology and electronics. Many activated phenomena, including solid state diffusion in crystals and polymers, dielectric relaxation, conduction and thermally stimulated processes in polymers, and electronic conduction in amorphous semiconductors obey the MN rule. In the present article, we report the MN rule in the non-isothermal crystallization in glassy Se80Te20 and Se75Te20M5 (M = Ag, Cd, In, Sb) alloys. We have observed MN rule between pre-exponential factor K o and activation energy of crystallization E c in the present case for thermally activated non-isothermal crystallization. 相似文献
66.
The structural and chemical properties with non-isothermal crystallization kinetics of PET–ZnO nanocomposites have been reported in this article. ZnO nanoparticles have been synthesized via chemical route with average diameter 19 nm which made confirm by transmission electron microscopy and X-ray diffractometer (XRD) techniques. PET–ZnO nanocomposites have been prepared by solution casting method. The structural and chemical changes occurred in poly (ethylene terephthalate) after inclusion of ZnO nanoparticles have been studied with the help of XRD and Fourier transform infrared spectroscopy, respectively. It was observed from differential scanning calorimeter that ZnO nanoparticles work as nucleating agent for heterogeneous nucleation in PET matrix under non-isothermal crystallization process. The combined Avrami and Ozawa models have been proved adequate to explain non-isothermal crystallization kinetics of PET–ZnO nanocomposites, and also, ZnO nanoparticles have been caused to reduce crystallization activation energy in pristine PET as per the applied Kissinger model. 相似文献
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69.
Shekhar KC Roshan K. Dhungana Namrata Khanal Prof. Ramesh Giri 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8124-8128
We report a Ni-catalyzed regioselective α-carbonylalkylarylation of vinylarenes with α-halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α-halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ-diarylcarbonyl derivatives with α-secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug. 相似文献
70.
A. Saraswat L. K. Sharma S. Singh I. R. Siddiqui R. K. P. Singh 《Russian Journal of Organic Chemistry》2013,49(9):1287-1290
Anodic fluorination of 4-methoxy-1-naphthol and 4-nitroanisole has been investigated in a mixed nonaqueous solvent using Et3N · 5 HF as supporting electrolyte as well as fluorine source. In order to avoid the formation of polymer on the anode, pulse electrolysis was carried out without exchanging the electrodes. The proposed procedure ensures excellent yield at room temperature, shortest reaction time, and easy work-up which provide additional advantages in the context of green chemistry. Experimental parameters of the reaction are discussed. 相似文献