广西龙塘蚀变流纹岩风化作用初期稀土元素地球化学研究

广西龙塘蚀变流纹岩在风化作用初期显示稀土元素一定的富集,但与风化母岩相比,稀土元素并未显示出分异特征.研究发现初期风化样品的针铁矿有微米大小的稀土磷酸盐矿物水磷铈石产出.电子探针能谱分析表明,水磷铈石以富铈为特征,并未产生铈的分异作用,因此将其作为缺氧环境的证据是有问题的.     

硫酸钍-硫酸铈-水体系的溶解度图(25℃)

研究硫酸钍-硫酸铈-水体系在25°时的溶解度图。体系中的二条溶解曲线相交于双饱和点, 其组成为:Th(SO_4)_2,4.23％(重量);Ce_2(SO_4)_3,9.52％(重量)。当溶液中硫酸铈浓度增加时,硫酸钍的溶解度自1.82％增至4.23％。当硫酸钍的浓度增加时,硫酸铈的溶解度也自7.62％增加至9.52％。     

La1-xCexFeO3钙钛石高变催化剂的XPS研究

采用X射线电子能谱(XPS)实验技术，对具有钙钛石结构的稀土铁复合氧化物高变催化剂进行了研究。结果表明：在La1-xCsxFeO3钙钛石结构中，铈的价态为正四，镧的价态为正三，而铁为正二、正三混合价态，三价铁和二价铁的摩尔比与稀土镧铈的摩尔比具有很好的一致性；在钙钛石ABO3结构中，A位镧、铈能有效控制B位铁的价态。铁具有混合价态是La1-xCexFeO3催化剂具有较高变换催化活性的主要原因。La1-xCexFeO3表面上存在α吸附氧和β晶格氧两类氧种，随铈含量的增加，表面吸附氧增加。     

云南老王寨金矿区煌斑岩稀土地球化学特征

广泛分布于云南老王寨金矿区的煌斑岩可分为新鲜（弱蚀变）、蚀变、矿化三种,虽然碱种煌斑岩稀土含量范围、分配模式为相似的富轻稀土型,但在ＬＲＥ／ＨＲＥ、ＮＬａ／Ｙｂ等参数也存在一定的差异。新鲜煌斑岩稀土地球化学研究表明,本区煌斑岩为富集地幔不同部分熔融程度的产物;煌斑岩蚀变、矿化过程中稀土元素活动规律的质量平衡计算结果表明,该区煌斑岩的蚀变流休和矿化流体均含有一定量的稀土元素,这些流体主要为伴随煌斑岩     

抑制动力学分析法测定痕量铈

１引言研究了铈（Ⅲ）阻抑Ｈ２Ｏ２氧化水杨基荧光酮（ＳＡＦ）褪色的反应。反应对铈（Ⅲ）为一级反应，表观活化能为２８．７５ｋＪ／ｍｏｌ。据此建立了测定痕量铈的动力学分析法。测定条件为：ＳＡＦ：４．０ｘ１０－５ｍｏｌ／Ｌ，Ｈ２Ｏ２：０．０１０％，ＮａＯＨ：２．０ｘ１０－２ｍｏｌ／Ｌ，５０℃。线性范围０．０４～０．４４ｍｇ／Ｌ，检测限为０．０２ｍｇ／Ｌ。当溶液中的铈含量为０．１６ｍｇ／Ｌ时，３～８倍量的轻稀土，５～１１倍量的重稀土及同倍量铀和钍不干扰测定。２实验部分２．１试剂和仪器铈（Ⅲ）标准溶液：２０…     

邻苯二酚衍生物与稀土元素配位反应的研究（V）：3,4—二羟 …

研究了稀土元素铈（Ⅲ）离子与３，４－二羟基苯甲酸（Ｈ３Ｌ）在水溶液体系中生成羧基配位化合物的条件，表征其组成为Ｃｅ（Ｈ２Ｌ）２（ＯＨ）．３Ｈ２Ｏ。并研究了该配合物在一定条件下，铈离子由羧基配位反应变由为两个邻酚羟基配位的配合物（Ｃｅ（ＨＬ）ｎ的转型反应及氧化物铈（ＶＩ）配合物的反应。     

镧镨铈混合稀土在镁合金中替代富铈稀土可行性研究

通过用价格较低的镧镨铈混合稀土代替富铈混合稀土用于ZM3合金，稀土含量从2．5％～3．33％，通过测其抗拉强度，发现在随稀土含量的增加，其抗拉强度也相应增加，并且其抗拉强度达到GB1177-91标准，通过金相观察，并分析其原因，结果认为：就抗拉强度而言，用镧镨铈混合稀土取代富铈混合稀土是完全可行的。     

褐藻多糖铈配合物对质粒DNA及牛血清白蛋白的裂解作用

以褐藻糖胶、褐藻酸及褐藻演粉为配体，分别与四价的铈（Ce^4 ）结合，形成了水溶性的褐藻多糖铈配合物，在生理中性条件下，它们对牛血清白蛋白（BSA）均有一定的裂解作用，但对质粒DNA（Plasmide DNA）仅有褐藻淀粉铈配合物有非常明显的裂解作用。     

铈的比色测定

本文在溶液pH值为1.2时在溴酸钾存在下的硝酸介质中,使铈水解为氢氧化高铈而分离,并加入硝酸钡以消除硫酸根对铈沉淀的影响;加入硝酸铵电解质以加速铈的沉淀,在钍、铊、钨、     

稀土对铝硅合金处理效果的研究

通过添加富镧、富铈、富钇和富钕混合稀土,考察了不同混合稀土加入量、不同冷却条件及其他因素对铝硅合金变质效果和含氢量的影响。结果表明,富钇、富镧、富铈混合稀土的变质效果依次减弱,富钕无明显变质效果。富铈、富镧、富钇和富钕混合稀土都能降低铝硅合金的含氢量,其去氢作用依次递减。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

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%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.