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本文应用脉冲Fourier交换核磁共振仪直接测定了若干种钴(Ⅲ)螯合物的~(59)Co-NMR谱。观察了溶剂、浓度、温度对~(59)Co谱的影响。以~(59)Co谱鉴别了螯合物的旋光和几何异构体,对于Co(±pn)_3Cl_3配合物,△(λλλ)和Λ(δδδ)峰在较低场,δ_(mer)大于δ_(fac),其次为△(λλδ)和Λ(δδλ)。分辨出Co(en)_3Cl_3从D_0至D_(12)十三个同位素异构体~(59)Co峰,每一个H/D交换使~(59)Co峰向高场移动5.4ppm,讨论了影响同位素位移方向、大小的诸因素及同位素位移的加和性,并讨论了化学平衡同位素效应。 相似文献
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在溶解度参数理论中,聚合物-溶剂的相互作用参数X_1计算式为: X_1=V_1/RT(δ_1-δ_2)~2+β (1)式中V_1为溶剂的摩尔体积,δ_1和δ_2分别为溶剂和聚合物的溶解度参数。经验常数β是作为对Flory组合熵的改进而计入X_1中的。 相似文献
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合成了 trans-PtHX(AsPh_3)_2(X=Cl~-、Br~-、I~-、SCN~-)四个配合物,除 trars-PtHCl(AsPh_3)_2外,其余三个为新配合物。用 NMR 和 IR 谱鉴定了结构和 trans-PtHSCN(AsPh_3)_2 的键合异构。研究了配体(X)对铂-氢化学位移(δ_H)和铂-氢偶合常数(J_(Pt-H))的影响、铂-氢键键长与铂-氢化学位移(δ_H)的关系以及铂-氢化学位移(δ_H)与铂-氢伸展振动频率的相关性。发现 trans-PtHCl(AsPh_3)_2 在不同溶剂中的重结晶产物,其 Pt-H 键的红外伸展振动频率不同,而 ~1HNMR 谱(在 CDCl_3 中)完全一样。 相似文献
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电子密度离域化问题即氮的孤对电子离域化问题,通常用动态核磁来研究,测量沿着这个键转动的势垒。在不同的温度下进行测量以得到活化热焓△H和活化熵△S。要确定氮的化学位移和其电子离域间的关系,进而推广到有机化合物的衍生物 相似文献
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《化学研究与应用》2021,33(9)
采用热重分析仪研究酚醛树脂保温板粉体热解行为。采用lnln法探讨等温热解过程动力学,采用Eyring方程探讨热解活化热力学参数。结果表明:酚醛树脂保温板粉体,在800℃内,非等温热解分为四个阶段,各阶段失重率依次为9%、10%、24%、25%;低于523K和高于573K时等温过程热解失重率低于523-573K温度段。lnln法获得酚醛树脂保温板粉体热解表观活化能为40.36 kJ·mol~(-1);Eyring法获得热分解的摩尔活化焓△H~≠、摩尔活化熵△S~≠分别为35.87 kJ·mol~(-1)和-202 J·mol~(-1)·K~(-1),摩尔活化自由能△G~≠值在讨论温度范围内皆为正,表明热解过程需要引入热量并且为非自发分解反应,热解需要经历活化络合态且络合态系统比初始状态更有序。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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《Tetrahedron》2014,70(21):3377-3384
The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献