溶剂浮选缔合物光度法测定痕量硒

根据亚硒酸 ( H2 Se O3)氧化 I-生成 I2 ,I2 与 I-配阴离子 ,I-3 ,配阴离子I-3 与孔雀绿阳离子 ( MG+ )发生离子缔合反应 ,用 N2 气将此缔合物浮选的三元缔合物用光度法测定硒。方法的 ε为 2 .2× 1 0 6L· mol-1· cm-1,RSD为2 .7% ,检出限为 4.7× 1 0 -10 g· m L-1     

硒(Ⅳ)-硫氰酸钾-甲基紫萃取光度法测定痕量硒

研究了硒(Ⅳ)与硫氰酸钾和甲基紫(MV)的显色反应,发现在pH=1.85的HCl介质中,[Se(SCN)_6)~(2-)与MV形成不溶解于水的三元离子缔合物,该缔合物可溶解于苯等有机溶剂,在苯溶液中,该缔合物的最大吸收峰位于600nm处,其摩尔吸光系数为1.18×10~5L/(mol·cm),硒(Ⅳ)浓度在0.0～6.0μg/25mL范围内符合比耳定律。该方法应用于合成水样和环境水样中硒的测定,结果准确、可靠。     

氮气-苯浮选光度法测定痕量锰

提出了根据 Mn( )氧化 I-生成 I2 ,I2 与 I-反应生成 I-3 配阴离子 ,I-3 配阴离子与孔雀绿阳离子发生离子缔合反应 ,用苯和 N2 将此缔合物浮选 ,以光度法测定此缔合物间接测量锰新方法。表观摩尔吸光系数为(ε=5.0 4× 1 0 5 L· mol-1· cm-1) ,测定 5.0μg/2 0 0 m L的锰 ( n=6 ) RSD为 1 .8%。已用于水中锰的测定。     

高灵敏分光光度法测定食品中痕量硒—硫氰酸盐—罗丹明B—Tween20体系

本文研究了Se(Ⅳ)-SCN-RhB-吐温20高灵敏显色反应体系。Se(Ⅳ)与SCN~-和RhB~+形成三元离子缔合物,并吸附了染料琉氰酸盐,表观摩尔吸光系数2.0×10~6L·mol~(-1).cm~(-1),是碱性染料类分光光度法中最灵敏的。Se含量在0～2μg/25ml范围内遵从比尔定律。利用巯基棉分离干扰离子,选择性高。测定了食品中总硒,结果满意。     

苯并-18-冠醚-6和溴百里香酚蓝离子对萃取光度法测定钾

报道了以苯并 18 冠醚 6 K+ 与溴百里香酚蓝显色体系光度法测定钾的研究。一定条件下 ,苯并 18 冠醚 6与钾离子形成络合阳离子 ,与阴离子溴百里香酚蓝形成离子对缔合物 ,被萃入氯仿中。该离子对缔合物于 4 10nm处有最大吸收 ,测定钾的摩尔吸光系数为 1.6× 10 4 L·mol- 1·cm- 1,钾含量在 0 .0 5～ 2 .5 μg·ml- 1范围内呈线性关系 ,相对标准偏差为 2 .2 %。应用于土壤、植物和血清中痕量钾的测定 ,与原子吸收光谱法相比 ,结果满意     

5-Br-PADAP为显色剂吸光光度法测定微量重铬酸根的研究

研究了 2 (5 溴 2 吡啶偶氮 ) 5 二乙氨基酚 (5 Br PADAP)在硫酸介质中质子化后与Cr2 O2 - 7形成二元离子缔合物的最佳条件 ,提出了测定微量Cr2 O2 - 7的吸光光度新方法 ,表观摩尔吸光系数ε580 =1.1× 10 5L·mol- 1·cm- 1。Cr2 O2 - 7浓度范围为 0～ 6 .2 4 μg·ml- 1。缔合物组成比为n(5 Br PADAP)∶n(Cr2 O2 - 7) =1∶1,方法应用于合金钢中铬的测定 ,结果满意     

丁基罗丹明B-硫氰酸盐-吐温-20体系高灵敏分光光度法测定微量硒的研究

本文叙述了在吐温-20存在下用硫氰酸盐和丁基罗丹明B形成缔合型三元配合物测定微量硒(Ⅳ)。配合物的最大吸收波长为600nm,硒含量在0—5μg/25ml服从朗伯比尔定律,其ε_(600)=6.4×10~5,重现性好,选择性高,是目前测定微量硒的一种高灵敏度的新的分光光度法,已用于水样中微量硒的测定。     

二氧化氯-碘化物-吖啶红高灵敏显色反应及其分析应用

在稀磷酸介质中 ,二氧化氯 ( Cl O2 )氧化 I- 形成 I3- ,I3- 进一步与吖啶红( ADR)阳离子形成离子缔合物 [ADR][I3]。在聚乙烯醇存在下 ,以试剂空白作参比 ,该离子缔合物的吸收波峰和波谷分别位于 5 82 nm和 5 2 6nm处 ,除波峰和波谷处吸光度与 Cl O2 的浓度有线性关系外 ,波峰和波谷的吸光度绝对值叠加也与 Cl O2 的吸光度呈直线关系。常规方法测定时 ,ε582 =1 .3× 1 0 5L· mol- 1· cm- 1;双波长法测定时 ,ε582 +52 6 =2 .9× 1 0 5L· mol- 1· cm- 1,对 Cl O2 的检出限分别为 0 .8μg/L和 0 .5μg/L。方法已成功地用于自来水中 Cl O2 的测定     

微乳液增敏光度法测定中草药中微量硒

研究了在非离子微乳液介质中,硫氰酸盐罗丹明B 明胶体系分光光度法测定微量硒的方法。实验表明,当微乳液组成为V(OP乳化剂) +V(正戊醇) +V(正庚烷) +V(水) =1 5 0 +0 1 1+0 41 +97 98时,体系的表观摩尔吸收系数达1 3 0 1×1 0 6 L·mol- 1·cm- 1,灵敏度比在OP溶液中有显著提高,使该法成为少有的超高灵敏度测定硒的光度法之一。Se (Ⅳ)含量在0～0 0 5 μg·mL- 1范围内符合比耳定律,对0 0 2 μg·mL- 1Se(Ⅳ)平行测定1 1次,测得相对标准偏差为0 945 %。应用于中草药中微量硒的测定结果令人满意     

银与碘化物和罗丹明B在水溶液中显色反应的研究

基于(AgIs)~2-络阴离子在聚乙烯醇存在下的水溶液中,与罗丹明 B 产生的离子缔合反应,提出了一个高灵敏度分光光度法测定银的方法.形成离子缔合物的适宜酸度范围是0～0.04N 硝酸(pH7～1.4).以连续变化法和平衡移动法确定离子缔合物的组成是[RB]_2[AgI_s].离子缔合物溶液的最大吸收位=j=600nm处,摩尔吸光系数为1.65×10~5·mol·~(-1)cm~(-1).方法有较好的选择性.在某些掩蔽剂存在下可用于钢中微量银的测定.     

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%.     

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.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.