读者园地

问 :金属材料中测定磷的方法有哪些 ?江苏读者———张宏　　答 :目前 ,大多数测定磷的方法是以形成磷钼杂多酸为基础的吸光光度法 ,其中包括直接光度法和萃取光度法。方法基于在酸性溶液中 ,使磷转化为正磷酸 (Ｈ3ＰＯ4 ) ,再与钼酸盐作用 ,形成 12 磷钼杂多酸。由于磷钼杂多酸呈淡黄色 ,其吸收峰位于近紫外区 ,而过量的钼酸盐在紫外区也有强烈吸收 ,因而通常选择合适的还原剂并在适宜的还原条件下 ,将磷钼杂多酸还原成磷钼杂多蓝。磷钼杂多蓝最大吸收位于可见区或近红外区 ,灵敏度较高 ,故得到广泛应用。当有钒、铋、锑等离子存在时 ,正…     

光度法测定磷铜中间合金中磷的氧化条件讨论

吸光光度法测定磷 ,无论是磷钼黄法还是磷钼蓝法 ,或是磷钒钼三元络合物法 ,都要求磷以正磷酸分子参加化学反应 ,所以把磷的各种低价化合物氧化为五价的正磷酸是光度法测定磷的首要条件。如不少分析方法中测定铜合金中磷也采取了用各种氧化剂氧化磷呈正磷酸尔后测定。测定磷铜中间合金中磷 ,文献 [1～ 3]均采用磷钒钼三元络合物方法 ,该法简单、快速、准确、重复性好 ,倍受分析工作者欢迎。分析方法采用混合酸(ＨＮＯ3∶ＨＣｌ∶Ｈ2 Ｏ =32 0∶12 0∶5 6 0 )溶样 ,滴加Ｈ2 Ｏ2 氧化磷 ,加ＨＣｌＯ4 冒烟使磷进一步完全氧化为正磷酸 ,再进行…     

磷钼钒杂多酸光度法测定钒

磷钼钒杂多酸早已用于磷的光度分析,其它应用尚未见报道。本文提出利用磷钼钒杂多酸光度测定高速钢中常量的钒,共存元素中铬、钴的影响以试样空白扣除,钨的负干扰可采用经验系数补正,样中1％Si和1％Nb不干扰测定。方法简便、快速、准确。本文还提出了在一定条件下形成磷钼钒酸、磷钨钒酸和磷钨钼酸的经验规律。 1 试剂与仪器 钼酸铵溶液:53g·L~(-1) 盐磷混酸:1.19g·ml~(-1)盐酸+1.74g·ml~(-1)磷酸=3+2 钒标准溶液:0.900mg·ml~(-1)(里偏钒酸铵配制并以滴定法标定) 721型分光光度计 2 分析方法称取试样0.1000g于200ml锥形瓶中(同时称一份不含钒的钢样作试剂空白A_0),加盐磷混酸1.5ml,硫酸(1+1)8ml,加热溶解,滴加浓硝酸助溶,继续加热     

分光光度法测定稀土磷矿浸出液中磷的含量

采用钼钒酸铵分光光度法对含稀土磷矿浸出液中磷的测定进行了研究,通过实验考察了显色剂用量、硝酸酸度对测定磷的影响,同时还考察了方法的准确度与精密度。实验结果表明,方法的精密度良好,相对标准偏差均小于3%,并与重量法测定磷进行对比分析,两者测定结果基本一致。方法可以准确地检测伴生稀土磷矿浸出液中磷,为考察稀土磷矿湿法冶金过程中的磷浸出率提供了一种简便、快速准确的分析方法。     

钼蓝分光光度法测定钼铝与钒铝合金中的硅

采用硝酸、氢氟酸分解试样,钼蓝分光光度法测定钒铝、钼铝合金中的硅量。对试样分解、光度法测定条件及共存元素的干扰等进行了试验。将该法应用于6个钒铝、钼铝试样中硅量(0.04%~0.46%)的测定,结果的相对标准偏差(n=11)在1.2%~4.6%之间,加标回收率为97.4%~102.2%。同时进行了多家实验室间数据比对,结果一致。     

分光光度法测定钢铁中的磷

在利用磷钼蓝分光光度法测磷的含量时,由于磷钼蓝颜色极不稳定,致使测定结果不准确。为此,在显色后的溶液中加硫脲使颜色的稳定时间延长,提高了测试结果的准确性。     

杂多酸在葡聚糖凝胶表面吸附研究

本文研究了硅钼、黄、硅钼兰、磷钼兰四种杂多酸在葡聚糖凝胶表面的吸附行为，测定了吸附等温线，探讨建立相应的葡聚糖凝胶分光光度法的可能性。     

磷钼黄分光光度法测定磷系阻燃粘胶纤维中磷含量

建立了分光光度法测定磷系阻燃粘胶纤维中磷含量的方法,对测定条件进行优化。提出采用硫酸―过氧化氢湿法消解磷系阻燃粘胶纤维的消解体系,使用磷钼黄分光光度法测定磷含量。结果表明:在最优化条件下,磷元素在0.00 mg/L~10.0 mg/L范围内呈线性关系,相关系数为R~2=0.999 8,加标回收率为83.3%~111%,测定结果的相对标准偏差为2.0%~2.4%。该方法用于测定阻燃粘胶纤维中磷含量操作简单、快速、准确。     

分光光度法测定低合金钢中钒

正钒在0.5~1.20mol·L~(-1)的磷酸介质中与2-(5-溴-2-吡啶偶氮)-5-二乙氨基苯酚(5-Br-PADAP)和过氧化氢生成三元配合物,其稳定性很高,一旦生成就不会被乙二胺四乙酸-柠檬酸铵破坏。低合金钢中常见的铁、铝、铬、锰、镍、铜、钛、钼等常量元素形成的配合物较易被分解,据此采用分光光度法测定钒。本工作对5-Br-PADAP-H_2O_2三元配合物测定钒的条件进行了探讨,与钽试剂一氯甲烷萃取光     

土壤速效磷的流动注射光度分析

磷作为作物生长发育必需的营养元素 ,历来被作为土壤肥力水平高低的标志之一。发达国家几乎每年都对土壤的养料状况进行测定 ,根据测定值及土壤与气候条件制订施肥建议。而土壤中速效磷的测定通常采用ＮａＨＣＯ3提取 ,磷钼蓝法和磷钼蓝萃取分光光度法[1 ] 测定。也有采用阴离子交换树脂提取法和同位素交换法[2 ] 。同位素交换法不适于测定高固磷土壤 ,分光光度法手工操作 ,耗时长 ,也不能实现自动分析。本文采用乙基紫 钼酸铵 ＯＰ络合显色的反应体系[5,6] ,流动注射分析技术 ,确立了土壤中速效磷的快速自动分析方法。用于实际样品分析 ,结…     

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.     

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.     

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.     

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.