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141.
Mohammad M. Mojtahedi Mohammad Saeed Abaee Mohammad Mehdi Zahedi Mohammad R. Jalali A. Wahid Mesbah Werner Massa Roholah Yaghoubi Mehdi Forouzani 《Monatshefte für Chemie / Chemical Monthly》2008,139(8):917-921
A remarkably efficient procedure for the synthesis of styrylcyclohex-2-enone derivatives at room temperature is described
using a mild reaction medium consisting of lithium perchlorate and N-(trimethylsilyl)diethylamine. Several compounds of this class are synthesized conveniently and rapidly. Spectroscopic and
X-ray diffraction experiments confirm the proposed structures.
Correspondence: Mohammad M. Mojtahedi and Mohammad Saeed Abaee, Organic Chemistry Laboratory, Chemistry and Chemical Engineering
Research Center of Iran, P.O. Box 14335-186, Tehran, Iran. 相似文献
142.
Giuseppe Bartoli 《Tetrahedron letters》2008,49(16):2555-2557
A new protocol for the Knoevenagel condensation between β-diketones and aliphatic and aromatic aldehydes promoted by Mg(ClO4)2 under mild conditions is reported. 相似文献
143.
L-脯氨酸独有的亚胺基使其在生物医药领域具有许多独特的功能,并广泛用作不对称有机化合物合成的有效催化剂。本文在碱性介质中研究了二(氢过碘酸)合银(III)配离子氧化 L-脯氨酸的反应。经质谱鉴定,脯氨酸氧化后的产物为脯氨酸脱羧生成的 γ-氨基丁酸盐;氧化反应对脯氨酸及Ag(III) 均为一级;二级速率常数 k′ 随 [IO4-] 浓度增加而减小,而与 [OHˉ] 的浓度几乎无关;推测反应机理应包括 [Ag(HIO6)2]5-与 [Ag(HIO6)(H2O)(OH)]2-之间的前期平衡,两种Ag(III)配离子均作为反应的活性组分,在速控步被完全去质子化的脯氨酸平行地还原,两速控步对应的活化参数为: k1 (25 oC)=1.87±0.04(mol·L-1)-1s-1,∆ H1≠=45±4 kJ · mol-1, ∆ S1≠=-90±13 J· K-1·mol-1 and k2 (25 oC) =3.2±0.5(mol·L-1)-1s-1, ∆ H2≠=34±2 kJ · mol-1, ∆ S2≠=-122 ±10 J· K-1·mol-1。本文第一次发现 [Ag(HIO6)2]5-配离子也具有氧化反应活性。 相似文献
144.
An efficient method for the synthesis of trifluoromethyl derivatives of endohedral gadolinium-containing metallofullerenes
was proposed. High-purity (98–99%) trifluoromethyl derivatives Gd@C82(CF3)5 (two isomers) and Gd2@C80(CF3) have been synthesized for the first time. They were isolated and characterized by HPLC, MALDI-TOF mass spectrometry, and
UV-Vis spectroscopy.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1457–1462, July, 2008. 相似文献
145.
Polymer bottlebrushes with monodisperse oligoproline side chains were efficiently synthesized, and the conformation of the peptide side chains in different solvents was investigated. Polymers with number-average degrees of polymerization (DPn) of 89 and 366 were obtained by polymerization of the macromonomer in iPrOH/MeCN (1:1) and hexafluoroisopropanol, respectively. Circular dichroism (CD) spectra of the bottlebrush polymers in the neutral and charged states reveal that the oligoproline side chains attain stable polyproline II (PPII) helical conformations not only in aqueous solution, but also in aliphatic alcohol solutions. Dense attachment of oligopeptides onto a linear polymer chain did not lead to an increase in helix content. The possible effects of the main-chain length on the conformational stability were examined. The switching between the polyproline I (PPI) and PPII helical conformations for the oligoproline side chains in aliphatic alcohol solutions is believed to be inhibited by the overcrowded structure in the polymer bottlebrushes. 相似文献
146.
采用差示扫描量热法(DSC)、热重和微分热重(TG-DTG)及固相原位反应池/快速扫描傅立叶变换红外联用技术(hyphenated in situ thermolysis/RSFTIR)研究了纳米结晶体Ni0.5Zn0.5Fe2O4与高氯酸铵(AP)组成的混合物的热行为和分解反应动力学。结果表明:Ni0.5Zn0.5Fe2O4使得AP的低、高温分解放热峰温分别提前17.44 K和27.74 K,并使得对应的分解热分别增加3.7 J·g-1和193.7 J·g-1。Ni0.5Zn0.5Fe2O4并不影响AP的晶转温度和晶转热。Ni0.5Zn0.5Fe2O4使得AP的TG曲线出现3个阶段,并使得后2个失重阶段的初始和终止温度都有所提前。凝聚相分解产物分析表明Ni0.5Zn0.5Fe2O4加速了凝聚相AP的分解及氨气的释放。含Ni0.5Zn0.5Fe2O4的AP的高温分解反应的动力学参数Ea=238.88 kJ·mol-1,A=1018.59 s-1,动力学方程可表示为dα/dt=1018.99(1-α)[-ln(1-α)]3/5e-2.87×104T。始点温度(Te)和峰顶温度(Tp)计算得出AP的热爆炸临界温度值分别为:574.83 K和595.41 K。分解反应的活化熵(ΔS≠)、活化焓(ΔH≠)和活化能(ΔG≠)分别为:109.61 J·mol-1·K-1、236.49 kJ·mol-1及172.58 kJ·mol-1。 相似文献
147.
Back Cover: Imaging Glycosylation In Vivo by Metabolic Labeling and Magnetic Resonance Imaging (Angew. Chem. Int. Ed. 4/2016)
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Dr. André A. Neves Dr. Yéléna A. Wainman Dr. Alan Wright Dr. Mikko I. Kettunen Dr. Tiago B. Rodrigues Sarah McGuire Dr. De‐En Hu Flaviu Bulat Dr. Simonetta Geninatti Crich Dr. Henning Stöckmann Dr. Finian J. Leeper Prof. Kevin M. Brindle 《Angewandte Chemie (International ed. in English)》2016,55(4):1566-1566
148.
Elisabeth W. Leib Robert M. Pasquarelli Malte Blankenburg Martin Müller Andreas Schreyer Rolf Janssen Horst Weller Tobias Vossmeyer 《Particle & Particle Systems Characterization》2016,33(9):645-655
Zirconia microspheres synthesized by a wet‐chemical sol–gel process are promising building blocks for various photonic applications considered for heat management and energy systems, including highly efficient reflective thermal barrier coatings and absorbers/emitters used in thermophotovoltaic systems. As previously shown, pure zirconia microparticles deteriorate at working temperatures of ≥1000 °C. While the addition of yttrium as a dopant has been shown to improve their phase stability, pronounced grain growth at temperatures of ≥1000 °C compromises the photonic structure of the assembled microspheres. Here, a new approach for the fabrication of highly stable ceramic microparticles by doping with lanthanum, gadolinium, and a combination of those with yttrium is introduced. The morphological changes of the particles are monitored by scanning electron microscopy, ex situ X‐ray diffraction (XRD), and in situ high‐energy XRD as a function of dopant concentration up to 1500 °C. While the addition of lanthanum or gadolinium has a strong grain growth attenuating effect, it alone is insufficient to avoid a destructive tetragonal‐to‐monoclinic phase transformation occurring after heating to >850 °C. However, combining lanthanum or gadolinium with yttrium leads to particles with both efficient phase stabilization and attenuated grain growth. Thus, ceramic microspheres are yielded that remain extremely stable after heating to 1200 °C. 相似文献
149.
建立了水果中高氯酸盐的高效液相色谱-串联质谱分析检测方法。样品采用1%乙酸提取,C18固相萃取柱净化,Waters IC-Pak Anion HR(4.6 mm×75 mm)色谱柱洗脱,流动相为乙腈-100 mmol/L乙酸铵溶液(体积比60∶40),流速0.7 m L/min;液相色谱-三重四极杆质谱联用技术-电喷雾负离子监测模式检测,采用18O标记高氯酸根离子作为内标进行基质校正,内标法定量。结果表明:高氯酸盐在0.1~10.0μg/L范围内线性关系良好,定量下限为1.0μg/kg;在1.0,2.0,10μg/kg 3个加标水平下的回收率为92.5%~110%,相对标准偏差(RSD)为1.4%~5.4%。实际样品检测表明该方法准确可靠,适合于水果中高氯酸盐的测定。 相似文献
150.
Amphiphilic Ditopic Bis‐Aqua Gd‐AAZTA‐like Complexes Enhance Relaxivity of Lipidic MRI Nanoprobes
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Dr. Giuseppe Gambino Prof. Lorenzo Tei Dr. Fabio Carniato Prof. Mauro Botta 《化学:亚洲杂志》2016,11(15):2139-2143
Two amphiphilic mono‐ and dimeric GdAAZTA‐like chelates composed of stable bis‐aquo GdIII complexes (q=2) linked to one (for the monomer) or two dodecyl aliphatic chains (for the dimer) were synthesized. Both chelates showed high relaxivity when incorporated into the lipid bilayer of liposomes or after interaction with human serum albumin (HSA). The ditopic complex shows a significantly decreased internal motion relative to the monomeric complex, associated with an enhanced relaxivity (r1≈60 mm ?1 s?1, at 30 MHz and 310 K). The presence of two metal‐bound water molecules in fast exchange and the restricted rotational freedom make the relaxivity of this system the highest measured for paramagnetic liposomes. 相似文献