5-Br-DMPAP-PVA124体系双波长光度法同时测定废水中钴和镍

研究了在PVA124存在下，用5-Br-DMPAP作显色剂，应用双波长吸光光度法同时测定钴和镍。选择镍波长对588／554nm，钴波长对473／582nm，当pH为9时，镍含量在0～8μg／25m1，钴含量在0～12μg／25ml范围内符合比耳定律。此法用于废水中微量钴和镍的同时测定，取得了较满意的结果。     

双波长分光光度法测定钴和镍

双波长分光光度法应用于性质相近离子的同时测定,要求在吸收光谱曲线上有良好的同吸收点。(4-(2-吡啶偶氮)间苯二酚(PAR)与钴(Ⅱ)镍(Ⅱ)离子所形成络合物的稳定吸收光谱曲线,为应用双波长分光光度法的测定,提供了有利的条件。我们以PAR为显色剂,在柠檬酸盐介质中,用751型分光光度计,顺利地实现了钴和镍共存时双波长分光光度法的测定。方法简便,为湿法冶金及钴和镍共存体系中钴,镍的分别测定提供了良好的方法。     

荧光分光光度法测定水中痕量钴和镍

试验合成了一种荧光试剂对-氨-苯基卟啉(TAPP),该试剂与钴(Ⅱ)离子和镍(Ⅱ)离子反应发生荧光淬灭,据此试验了以其为探针测定痕量钴(Ⅱ)和镍(Ⅱ)的荧光分光光度法。在pH7.2的Tris-盐酸缓冲介质中,在一定量的十二烷基硫酸钠(SDS)存在下,通过测定样品溶液和空白溶液在激发波长392 nm和发射波长516 nm处的发射荧光强度F_s及F_0,计算得反应液荧光强度减弱程度△F,其结果表明:△F与钴(Ⅱ)和镍(Ⅱ)的浓度均在2.0×10~(-7)～1.0×10~(-5)mol·L~(-1)范围内呈线性关系,方法的检出限(3S/N)分别为2.0×10~(-8)mol·L~(-1)和4.0×10~(-8)mol·L~(-1)。此方法用于自然水体和污水中钴(Ⅱ)和镍(Ⅱ)的测定,回收率分别在97.0%～108.5%和97.0%～106.5%之间。     

两次双波长分光光度法同时测定原油中的镍和钒

采用系数补偿和双峰双波长的两次双波长分光光度法,以5-B r-PADAP为显色剂、Triton X-100为增溶增敏剂,同时测定原油中N i(Ⅱ)和V(Ⅴ)。N i(Ⅱ)和V(Ⅴ)的线性范围分别为:0~15μg/(25 mL)和0~10μg/(25mL),回收率分别为95.0%~103.0%、96.0%~101.5%,测定结果的相对标准偏差分别为0.39%、3.33%。     

激光热透镜光谱分析法同时测定铜、钴和镍研究

基于2-(5-NO2-吡啶-2-偶氮)-1-羟基-8-氨基萘-3，6-二磺酸与铜(Ⅱ)、钴(Ⅱ)和镍(Ⅱ)反应酸度的差异及热透镜信号强度的加和性，建立了激光热透镜光谱法同时测定铜、钴和镍的新方法。测定铜、钴和镍的线性范围依次为0～200ng/mL、0～200ng/mL和0～100ng/mL，检出限依次为2ng/mL，2．5ng/mL和1ng/mL。方法已用于合成样品及人发样中铜、钴和镍的同时测定。     

K系数分光光度法同时测定钴矿中铜、钴、镍

探讨了在pH 8.00时,溴化十六烷基三甲基铵在存下,铜(Ⅱ)、钴(Ⅱ)和镍(Ⅱ)与二甲酚橙显色的反应条件.建立了K系数分光光度法同时测定钴矿中铜、钴、镍的分析方法.铜、钴、镍含量分别在0～800 μg·L-1,0～1.60 mg·L-1,0～1.20 mg·L-1范围内符合比耳定律.方法用于钴矿试样的分析,测得铜、钴、镍的相对标准偏差分别为3.5%,4.9%,3.4%,回收率分别为103.3%,92.6%,99.0%.     

分光光度法同时测定微量铁和钴

在碱性介质中,铁(Ⅱ)和钴(Ⅱ)可与硫代巴比妥酸-NO2-体系反应分别形成一种稳定的兰色和黄色配合物,铁(Ⅱ)配合物在656nm和386nm具有吸收峰,钴(Ⅱ)配合物只有一个吸收峰位于423nm,体系的吸光度A6Fe56、A4F2e3、AC42o3与铁、钴含量在一定的范围内呈良好的线性关系,且铁(Ⅱ)、钴(Ⅱ)配合物在423nm波长处的吸光度具有良好的加和性,建立了一种同时测定微量铁和钴的新的分光光度法。方法的线性范围分别为铁0～50μg/(25mL)、钴0～25μg/(25mL)。将该法应用于水样中微量铁和钴的同时测定,其结果分别与原子吸收光谱法和紫尿酸光度法相吻合,加标回收率分别为98%～102%和94%～106%,相对标准偏差(RSD)分别为1.0%～1.8%和3.1%～4.7%(n=5)。     

薄层色谱法测定痕量的镍(Ⅱ)、铜(Ⅱ)、镉(Ⅱ)、钴(Ⅱ)、锌(Ⅱ)的研究

在pH值为9.5～9.9的氨-氯化铵的缓冲溶液中,镍(Ⅱ)、铜(Ⅱ)、镉(Ⅱ)、钴(Ⅱ)、锌(Ⅱ)形成氨合络合物,而银(Ⅰ)、铋(Ⅲ)、铁(Ⅲ)、铁(Ⅱ)、汞(Ⅱ)、汞(Ⅰ)、锰(Ⅱ)、铅(Ⅱ)、锡(Ⅳ)、锡(Ⅱ)、钒(Ⅴ)、铝(Ⅲ)、钛(Ⅳ)等生成各种形式的沉淀。用甲醇-乙醇-氯化铵-氨-水体系(pH9.0～9.1),在硅胶H薄层板上,可以实现镍(Ⅱ)、铜(Ⅱ)、镉(Ⅱ)、钴(Ⅱ)、锌(Ⅱ)的分离。双硫腙显色后,用CS-930双波长薄层扫描仪测定含量。线性范围:锌0.01～0.20微克,铜0.01～0.25微克,镍、镉、钴0.01～0.30微克。     

非离子表面活性剂存在下2-[2-(5-溴苯并噻唑)偶氮]-5-二甲氨基苯甲酸分光光度法测定微量镍

本文合成了新显色剂,2-〔2-(5-溴苯并噻唑)偶氮〕-5-二甲氨基苯甲酸(5-Br-BTAMB),研究了在Triton X-100存在下它与镍的显色反应。发现在Triton X-100存在下,镍(Ⅱ)与5-Br-BTAMB形成稳定的蓝色配合物,其组成为Ni(Ⅱ):5-Br-BTAMB=1:2,最大吸收波长为655nm,表观摩尔吸光系数为1.47×10~5L·mol~(-1)·cm~(-1),镍的浓度在0～10μg/25ml范围内服从比尔定律。本方法灵敏度高,选择性好。大多数金属元素不干扰镍的测定,只有钴、铜和钯有干扰,其中铜和钯的干扰可用硫脲掩蔽,用于测定铝合金中微量镍取得满意结果。     

镍(Ⅱ)-PAN-吐温80分光光度法测定原油中的镍

以 1 (2 吡啶偶氮 ) 2 萘酚 (PAN) -吐温 80为显色体系测定原油中的镍。配合物的最大吸收波长为 5 6 8nm ,表观摩尔吸光系数为 5 .3× 10 4L/ (mol·cm)。镍含量在 0～ 14 μg/ (2 5mL)范围内服从朗伯 -比耳定律。以三乙醇胺和硫脲作为掩蔽剂 ,可消除原油中铁 (Ⅲ )、钴 (Ⅱ )、铜 (Ⅱ )、钒 (V)等离子的干扰。人工合成样品的平均回收率为10 2 .12 % ,测定结果的相对标准偏差为 1.83%。两种原油样品中镍含量测定结果的相对标准偏差分别为 1.37%、2 .12 % ,加标回收率分别为 97.6 7%、98.76 %。     

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.     

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%).     

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.     

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.