石墨炉原子吸收光谱法测定痕量钒的研究

本文采用石记原子吸收光谱对钒吸收线的特征，普通石墨管和热解石墨管中钒的原子化行为，灰化和原子化条件，基体效应等进行了研究，综合应用基体改进剂，光控升温和解石墨管技术，提高了电热原子吸收测定钒的灵敏度，特征质量为２４ｐｇ／０．００４４Ａ。     

用N-263从钒溶液中回收钒

测定了N－263对钒的饱和萃取容量，考察了萃取容量与溶液中钒阴离子离子状态的关系及各种因素对N－263萃取钒的影响，作了萃取平衡图，拟定了用萃取法从含钒溶液中提取钒的工艺流程。     

间硝基氯磺酚与钒（Ⅴ）的显色反应研究及应用

研究了间硝基氯磺酚与钒的显色反应。试验表明，以六次甲基四胺为缓冲溶液，钒（Ⅴ）与间硝基氯磺酚能形成稳定的络合物，其最大吸收波长λｍａｘ＝６２５ｎｍ，表观摩尔吸光系数ε＝３．６９×１０４，钒（Ⅴ）与间硝基氯磺酚的络合比为１∶３，钒含量在０～２１ｍｇ／２５Ｌ范围内符合比尔定律，用本法测定合金钢中的钒，结果令人满意。     

碱熔-电感耦合等离子体原子发射光谱法测定废弃加氢脱硫(HDS)催化剂中的钒

本文建立了碱熔-电感耦合等离子体原子发射光谱法（ICP-OES）测定废弃加氢脱硫（HDS）催化剂中钒的方法,来协助加氢脱硫（HDS）催化剂回收实验的进行。试验采用过氧化钠熔解试样,用盐酸浸取后定容,稀释试液后控制盐酸酸度为10%,并选择钒292.401 nm为分析谱线。试验结果表明,为了消除基体效应的影响,需要使试液中钠元素、盐酸的含量和标准溶液中的钠元素、盐酸的含量相同。钒质量浓度在1.00-20.00 μg/mL时与发射强度呈线性关系,相关系数均为1。按照上述方法测定了5个废弃加氢脱硫（HDS）催化剂样品中的钒,并采用格拉布斯检验方法检验11次,测定结果无异常值,加标回收率为99%-101%。该方法有效解决了废弃加氢脱硫（HDS）催化剂中钒测定的难题,可用于测定钒质量分数为0.50%-10.00%的HDS催化剂,同时对其他产品中钒的测定提供一种新思路。     

离子色谱法测定钒酸根离子的研究

研究了离子色谱测定钒酸根离子的方法。用紫外－可见检测器对钒酸根离子进行了检测,并考察了Ｖ（Ⅴ）－ＰＡＲ显色反应的影响因素,确定了检测钒酸根离子的最佳条件。以此法测定钒酸根离子的检出限为４．０×１０~（－３）ｍｇ／Ｌ,相对标准偏差为１．８％,测定合成水样结果与电感藕合等离子体原子发射光谱分析法（ＩＣＰ－ＡＥＳ）测定结果相比较并进行ｔ和Ｆ检验,无显著性差异。     

催化离子选择电极联合测定天然水中钒铁钼的方法研究

利用在硫酸介质中过氧化氢氧化碘化物的反应，加入抗坏血酸产Ｌａｎｄｏｌｔ反应，钒、铁、钼可催化此反应，以碘离子选择电极为监测器，由诱导期测得钒、铁、钼总量，用ＥＤＴＡ掩蔽铁测得钒和钼量，最后用柠檬酸掩蔽铁和钼测得钒量；利用差减法分别求得钒、铁、钼量。将方法用于天然水中钒、铁、钼的测定，结果令人满意。     

溴酸钾氧化α—萘红催化光度法测定痕量钒

１引言在环境化学中，钒是重要的微量元素，而样品中钒含量通常很低。近年来有不少动力学测定痕量钒的方法报道，多用钒催化ＫＢｒＯ３氧化某指示剂褪色，活性剂能改善测定灵敏度，用过的活化剂有酚、抗坏血酸、柠檬酸等。我们曾用酒石酸作活性剂，以钒催化ＫＢｒＯ３氧化二甲基黄，得到了很高灵敏度。本文所用的α－萘红是一种酸碱指示剂，我们将其作为动力学分析的新指示剂，溴酸钾氧化，钒催化，以草酸钠作为新活化剂，提高了灵敏度，并且通常干扰钒测定的Ｆｅ３＋、Ｃｕ２＋、Ｍｎ２＋等可有效抑制，提高了选择性，用于水及食品中痕量钒…     

脉冲加热-红外吸收光谱法测定钒铝合金中氢

对脉冲加热-红外吸收法测定钒铝合金中氢的分析方法进行了研究。通过实验对分析功率、称样量和校正标样等测试条件进行了讨论。实验表明钒铝合金中的氢易释放,对于AlV85样品中氢,热提取法和熔融法测定结果一致;但AlV50样品中氢,热提取法的结果略高于熔融法,故实验中选用热提取法测定钒铝合金中氢量。热提取法用0.75g金属锡作助熔剂,于4.0kW分析功率条件下测定钛标准样品中氢来确定氢工作曲线的校正系数,在1.5kW分析功率下测定钒铝合金中氢,测定结果与高频感应-热导法(用5g钢标准样品对氢的测定进行校正)结果吻合。对3个钒铝合金中氢量进行了测定,结果的相对标准偏差为2.2%～6.5%(n=8)。     

用新显色剂PMNHA分光光度测定钒钛铁矿及其冶炼炉渣中的钒

建立了一个高选择性和简便的用显色剂N-苯基-1-甲氧基-2-萘甲酰氧肟酸(PMNHA)分光光度测定钒的方法。该试剂的三氯甲烷溶液能迅速地从2.25—4.50M盐酸中萃取钒(V)的紫色配合物。其配合物最大吸收在540nm,钒(V)与PMNHA的摩尔比为1:2,很多外来离子,特别是大量的钛不干扰钒的测定。钒含量在0—28ppm范围遵守比耳定律。本文拟定的测钒操作方法,简单、快速、准确,用若干标样核对,测得结果与推荐值很符合。     

硫酸亚铁铵滴定法测定低品位石煤钒矿中的五氧化二钒

建立硫酸亚铁铵滴定法测定低品位石煤钒矿中五氧化二钒含量的方法。将石煤钒矿样品在920℃下灼烧20 min进行预处理,以驱除石煤钒矿石中的含碳化合物和有机物,通过酸度调节,实现滴定终点的突跃。用硫酸亚铁铵滴定法测定样品中五氧化二钒的含量。测定结果的相对标准偏差为0.43%(n=10),用该法测定国家标准物质和实验室内控样品,测定值与参考值一致。该方法具有较高的准确度和良好的精密度,适宜于低品位石煤钒矿中五氧化二钒含量为0.5%以上样品的测定。     

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.     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.