X射线衍射定量相分析新方法

在基体清洗法的基础上提出一种新的X射线衍射定量分析方法，该方法是利用混合样品X射线衍射谱图中的全部衍射峰数据，把清洗剂同样品中所包含的所有待测物相的纯相按比例混合，在同一水平下同时测定各物相与清洗剂对应的几个K值，结合JCPDS卡中的各相标准谱峰的相对强度分布数据进行最小二乘方程组的抛弃平均法回归分析，求得混合物样品中各相间的全谱峰匹配强度比，用于混合物样品的X射线衍射定量相分析，有利于提高定量相分析的精度，通过对四组分混合物样品的分析，实验结果和理论完全一致。     

粘胶纤维微细结构的定量研究

<正> 前言粘胶人造丝超分子结构与物理性能之间的关系,直到最近仍然是许多学者所关心的重要课题。但是,粘胶纤维的 x 射线衍射图谱中各晶相衍射峰和非晶相散射峰互相重叠,一直无法分开,妨碍了对其微细结构进行定量研究。70年代以来,发展了用电子计算机分解谱线叠加峰的数学方法,使解决该问题成为可能。     

X射线衍射法钾混盐无标样定量相分析

采用EVD、TOPAS应用软件和TOPAS结构数据库以及无机晶体结构数据库,对一些混合盐样品(如钾混盐、尾矿等)进行了X射线粉末衍射无标样定量相分析全谱拟合模拟研究。在用Rietveld分析法对上述样品中无机盐成分的X射线衍射谱进行模拟过程中,选择基本参数函数为峰形函数,并通过March-Dolase择优取向校正拟合,提高了拟合精度。测得钾混盐样品中钾盐镁矾相含量为72.44%,岩盐相含量为27.56%,误差值Rwp(17.45),Rp(12.21)和拟合度S(4.91)均有所降低。     

X射线衍射定量相分析的检测限

X射线衍射定量相分析可以获得混合物中各物相的含量。混合物中各相的含量,由於吸收效应,一般不与其衍射线强度成正比关系,但含量与强度仍成一定的比例关系。在物相定性和定量分析中,人们对检测限是很感兴趣的。例如在常见的产物鉴定和相变研究中,通常需要知道物相的纯度。解决这个问题惯用的办法是将微量相含量一次一次减少地加入到基体中去,配制一系列不同标样,观察其衍射线强度;衍射线刚好消失时对应的含量,即为检测     

样品质量控制对X射线衍射测量结果的影响

以生物材料羟基磷灰石（HA）为样品模型,系统研究了HA样品在不同质量状态下对X射线衍射测试结果的作用。通过考察样品状态确认（块体、层状和粉末等）、实验方法选择（粉末多晶衍射和薄膜掠入射衍射等）以及环境条件控制（温度、湿度及X射线下辐照时间等）等因素,评价样品的质量控制对X射线衍射（XRD）检测数据准确性与真实性的影响。结果表明,与HA块状样品相比,经过研磨过筛处理后的粉末试样XRD特征峰强度显著增强,差异可增加至1倍以上。针对HA多层状生长样品,结合掠入射和常规粉末衍射可精准实现各层物相解析。HA粉末样品的粒径、样品量及对应的装填方式会影响XRD检测结果,粒径37μm的HA粉末样品的特征峰强是粒径137μm样品1倍左右;而少量样品的中部空置制样,可导致特征峰峰位由31.8（°）偏移至31.4（°）,峰强从11213.68降到601.65。另外,对于稳定性不佳或对环境温湿度敏感的试样,采取合适的保存和检测方式,可有效预防和避免错误的检测与结果分析。因此,全面的质量控制对高质量的XRD检测数据获取和确保实验数据质量至关重要。     

X射线吸收分析法简介

近十余年来,X射线化学分析法已被广泛采用。利用X射线进行化学分析,有三类不同方法:衍射分析法,发射光谱分析法和吸收分析法。衍射分析法常称物相分析,它是根据晶态物质的X射线衍射花样的特征和衍射线的强度来进行定性与定量分析的。分析结果直接给出样品中所含晶体的种类、数目及其相对含量。非晶态物质沒有一定的衍射花样,故不能用此法分析。发射光谱分析法(包括初级发射光谱法及熒光X光谱分析法)的原理与通常的光学光谱分析法相同,是根据各种元素所固有的特征X射线的波长及强度来进行定性定量分析的,分析结果给出样品中所含元素的种类及含量。上述二法本刊已先后作过介绍,本文之目的是要对吸收分析法的原理、设备及应用作一简要介绍。     

X射线光电子能谱中的分峰处理

文章详细介绍了X射线光电子能谱分峰操作的流程,对谱图中单峰和多峰的荷电位移、数据平滑、背景扣除、谱峰确认和多高斯拟合操作的数学流程进行了图解。我们认为,具有足够连续宽度和强度的峰值处才可以被判定为峰;谱图中可以进行含量定量的谱峰强度应在背景涨落的10倍以上;最后得到的分峰结果,还应进行统计检验。     

电子计算机自动X射线物相分析进展

利用X射线粉末衍射谱进行物相分析,由于不破坏样品,过程简单,结果准确可靠而成为化学化工、金属、地质及其它材料学科中最广泛使用的方法。 X射线物相分析是把待鉴定样品的衍射谱与一套物相已知的标准衍射谱进行对比,以确     

A1掺杂对尖晶石型Li[Mn（Al）]2O4结构的影响

采用共沉淀法按不同Al掺杂比例x[x=n(Al):n(Mn Al)=0,0.025,0.050,0.100,0.150,0.200]制得了Al(OH)3和Mn3O4混合物，将其与LiNO3按一定比例混合，在空气中于700℃烧结得Li[Mn(Al)]2O4样品，X射线衍射和Raman光谱结果表明，在0≤x≤0．20范围内均得到了单相的尖晶石型样品，随着x的增加，晶胞参数减小，晶格振动能量增加，Mn(Al)-O的结合增强，结构稳定性增强。     

Al掺杂对尖晶石型Li[Mn(Al)]2O4结构的影响

采用共沉淀法按不同Al掺杂比例x[x=n(Al)∶n(Mn+Al)=0, 0.025, 0.050, 0.100, 0.150, 0.200]制得了Al(OH)3和Mn3O4混合物, 将其与LiNO3按一定比例混合, 在空气中于700 ℃烧结得Li[Mn(Al)]2O4样品. X射线衍射和Raman光谱结果表明, 在0≤x≤0.20范围内均得到了单相的尖晶石型样品, 随着x的增加, 晶胞参数减小, 晶格振动能量增加, Mn(Al)-O的结合增强, 结构稳定性增强.     

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%.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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 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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.