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81.
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A new fluorescent ‘‘on–off' chemosensor for Hg2+initiated by a derivative of rhodamine B was designed and synthesized. Compound 1 exhibited high sensitivity and selectivity for Hg2+over other commonly coexistent metal ions in aqueous media. Upon the addition of Hg2+, the spirocyclic ring of probe is opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm is observed. The colorimetric and fluorescent response to Hg2+can be conveniently detected by the naked eye, which provides a facile method for visual detection of Hg2+. From the molecular structure and spectral results of 1, an irreversible, hydrolysis, desulfurization reaction mechanism is proposed. 相似文献
84.
Uridine 5′-oxyphosphorane was synthesized by the reaction of 2′, 3′-di-O-acteyluridine 5′-diisopropyl phosphite with tetrachloro-1, 2-benzoquinone. 相似文献
85.
Kui Lu Guang-Zhong Tu Xiang-Feng Guo Xiao-Bin Sun Yan Liu Yu-Ping Feng Yu-Fen Zhao 《Journal of Molecular Structure》2002,610(1-3):65-72
A stable penta-coordinated serine-carboxylic-phosphoric anhydride may be synthesized at temperatures below −18 °C. Above that temperature, the product was shown to isomerize to another penta-coordinated phosphorus compound, which was proven by the change in the magnitude of observed P–C coupling constants. The mechanism for the anhydride to ester isomerization might provide a clue to the proposal of high-energy supply for biochemistry. Organic bases were shown to exert little influence on the rate of isomerization. 相似文献
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87.
In this paper, 5?-O-tosyl-2,3?-anhydrothymidine has been synthesized and its crystal structure was analyzed. The crystal belongs to the triclinic system, space group P1, with a = 5.397(2), b = 6.1886(18), c = 3.507(5) ?, α ?= 87.74(2), β ?= 89.84(4), γ ?= 73.79(2)°, C17H18N2O6S, Mr = 378.39, Z = 1, V = 432.8(3) ?3, Dc = 1.452 g/cm3, F(000) = 198 and Flack = -0.11(14). No intermolecular hydrogen bonds exist in the crystal, and the angle between benzene ring and pyrimidine planes is 32.23°. 相似文献
88.
Xu PX Hu AF Hu D Gao X Zhao YF 《Rapid communications in mass spectrometry : RCM》2008,22(19):2977-2983
Several O-2',3'-isopropylideneuridine-O-5'-phosphoramidate monoesters were synthesized and analyzed by negative ion electrospray ionization tandem mass spectrometry (ESI-MS(n)). Two kinds of novel rearrangement reactions were observed due to the difference in the amino acid in the nucleoside phosphoramidate monoesters, and possible mechanisms were proposed. One involves a five-membered cyclic transition state. The other is formation of a stable five-membered ring intermediate by Michael addition. Results were confirmed by tandem mass spectrometry and isotopically labeled hydrogen atoms. Furthermore, the internal hydrogen exchange between active hydrogen and methyl acrylate in the heated capillary of the mass spectrometer was found. The characteristic fragmentation behavior in ESI-MS may be used to monitor this kind of compounds in the biological metabolism. 相似文献
89.
90.
Yu-Fen HUANG Hai-Long ZHANG Zheng-Zheng YANG Ming ZHAO Mu-Lan HUANG Yan-Li LIANG Jian-Li WANG Yao-Qiang CHEN 《物理化学学报》2017,33(6):1242-1252
The catalytic activities for NO oxidation achieved by different amounts of CeO2-modified Pt/SiO2-Al2O3 catalysts Pt/SiO2-Al2O3-wCeO2 (the mass fraction w being 0%, 5%, 10%, 15%, 30%), prepared using step-wise impregnation, were investigated in the presence and absence of CO and C3H6. The results showed that the NO oxidation activity could be efficiently improved by modification of CeO2, wherein the 15%-CeO2-modified catalyst exhibited the maximum NO conversion of 61% even in the presence of CO and C3H6, which were proved to inhibit NO2 formation in this study. A series of characterization methods were performed over the as-prepared samples to correlate their surface and structural characteristics with their enhanced NO oxidation activities. CO-chemisorption illustrated that appropriate CeO2-loading was effective for enhancing Pt dispersion, thus enhancing Pt surface-to-volume ratio, confirmed by transmission electron microscope (TEM) images. X-Ray Diffraction (XRD) further suggested that ceria addition could suppress the growth of the Pt crystal, resulting in higher surface Pt atomic ratio. Further, H2 temperature-programmed reduction (H2-TPR), together with TEM results, implied that the presence of ceria could enhance the interaction between metal and supports, thus facilitating reducibility of both active platinum and ceria. Hence, this study displays that ceria could act as a dispersion promoter and a reducibility booster, both of which are beneficial to NO oxidation activity. The improved NO oxidation activity is significant for the efficient purification of diesel integrated catalytic system. 相似文献