钙镁和极弱酸的二次微分示波极谱滴定

示波极谱滴定法有它独特的优点,但在某些测定中,终点指示的灵敏度尚有待进一步提高。例如,用EGTA(乙二醇二乙醚二胺四乙酸)和HEDTA(N-β羟基乙基乙二胺三乙酸)滴定Ca~(2 )、Mg~(2 )时,过量滴定剂的切口变化不够敏锐。用强碱中和滴定极弱酸时,作为相应于pH≈11的指示剂的苯胺的切口变化不易判断。高次微分及电流反馈技术能克服这些缺陷。在(d~2E/dt~2)～E图上终点切口观察灵敏得多,Ca:Mg的比例可提高到100:1。在硼酸和苯酚测定中,测定下限较一次微分法降低了一个多数量级。     

天然水中硫酸根的交流示波极谱滴定

在NH_4Ac溶液中加入标准Ba~(2+)溶液沉淀SO_4~(2-)用标准K_2CrO_4溶液滴定过量Ba~(2+)。过量的CrO_4~(2-)在交流示波极谱图上出现切口指示终点,间接求出天然水中SO_4~(2-)含量。     

钾的交流示波极谱滴定

高含量钾测定,一般采用NaB(C_6H_5)_4-Hg(Ⅱ)-EDTA容量法。由于使用金属指示剂指示滴定终点,就要求溶液无色,无沉淀物等,而且终点不甚清晰。交流示波极谱滴定法则可克眼指示剂法的不足之处。本试验于强酸性介质中,加入NaB(C_6H_5)_4,使K~ 与(C_6H_5)_4B-生成沉淀,用丙酮溶解。加入过量Hg(Ⅱ)-     

示波极谱滴定的研究(ⅩⅩⅩⅦ)——双微铂电极示波极谱滴定的原理

本文对EDTA等试剂在双微铂电极示波极谱图上产生切口的原因进行了探讨。双微铂电极示波极谱图上EDTA的切口主要来源于EDTA在铂电极上的吸附,使氧在电极上的吸附过程受阻而降低了氧的还原电流,因而使每一个电极上的E_i～t曲线发生变形。双微铂电极上所得的E～t曲线是两个E_i～t曲线的叠加.因此在E～t曲线上出现了明显的折扭.在dE/dt～E曲线上出现切口。还解释了其它一些实验现象。     

乳酸环丙沙星的示波极谱滴定

１引言 乳酸环丙沙星（ＣＰＲＬ）为第三代氟喹诺四类抗生素,目前,其含量的测定主要有非水滴定法、紫外分光光度法、ＨＰＬＣ、极谱法等,但未见有示波极谱滴定法的报道。本法用四苯硼钠（Ｎａ－ＴＰＢ）作沉淀剂,在弱酸性（ｐＨ＝５．１）条件下与乳酸环丙沙星作用生成沉淀,过滤后,用硫酸亚铊标准溶液回滴滤液中过量的Ｎａ－ＴＰＢ,以ＴＰＢ在示波极谱图［ｄＥ／ｄｔ＝ｆ（Ｅ）］中的切口消失指示滴定终点。本法仪器简单,操作方便,取样量小,图形直观,终点敏锐,用于原料药样品的测定有良好的准确度和重现性,其结果与非水滴定法…     

维生素C的交流示波极谱滴定分析

在盐酸介质中 ,用K3 [Fe(CN) 6]标准溶液直接滴定Vc,以K3 [Fe(CN) 6]在交流示波极谱图上的切口出现指示滴定终点 .本法操作简便 ,灵敏准确 ,选择性强 ,应用于单方药物制剂Vc片剂和复方药物制剂感冒敏以及强力Vc银翘片中Vc的含量测定 ,结果满意     

工业废水中微量苯酚的交流示波极谱滴定

工业废水中微量污染物苯酚用交流示波极谱滴定可简单而快速地测定。准确分取部分过滤后的试样在氯化钾底液中以苯胺作指示剂,在不断搅拌下用0.020 00 mol.L-1氢氧化钾标准溶液滴定,用汞膜电极作指示电极,银汞电极为参比电极。苯胺的示波极谱图上出现切口时即为滴定终点。根据氢氧化钾标准溶液滴定的体积计算试样中苯酚的含量。此滴定至终点的溶液的pH值经预先试验测定为11.27,而6 g.L-1苯胺溶液1 mL在氯化钾底液中当出现切口时的pH值为11.3。苯胺在此方法中的作用为指示剂,以其示波极谱图上出现切口指示滴定终点。此方法应用于废水样品分析,回收率在97.3%~104.0%之间。     

再论极弱酸(碱)水溶液的直接测定

用通常的指示剂滴定法不能直接在水溶液中用强酸(碱)滴定极弱碱(酸)。陈淑萍等曾使用汞电极为工作电极,用指示剂切口的变化来指示交流示波极谱中和滴定的终点,在水溶液中直接进行极弱酸碱的滴定。但此方法存在以下缺点:(1)汞电极不适用于强酸性及氧化性溶液;(2)实验条件苛刻,要严格控制指示剂的滴数以确定滴定体积。庄建元等为了弥补汞电极的不足,进行了钻电极上的示波极谱中和滴定,但仅用HCl滴定了氨基比     

极弱酸碱的直接电位滴定

讨论了用两点电位滴定法直接测定pKn(或pKb)在10左右的极弱酸碱的可行性。该法只需在计量点后适当位置测定两组滴定数据，即可确定滴定计量点。与线性电位滴定法比较，两者结果一致。     

弱酸弱碱非线性回归电位返滴定的研究

本文提出的方法是在被测弱酸或弱碱溶液中加入一定量过量ＮａＯＨ或ＨＣｌ材料溶液，再返滴入ＨＣｌ或ＨａＯＨ材料溶液若干次，依次用电位法测定被测溶液中质子浓度，根据有关酸碱平衡和物料平衡原理及非线性回归原理对实验数据进行处理。     

固定pH法测定两组分极弱酸（碱）混合体系

将固定pH滴定法结合求解一元线性回归方程组应用于极弱酸(碱)混合体系中各组分含量的同时测定。测定了六次甲基四胺-硫酸钠和六次甲基四胺-乙酸钠混合体系中各组分的含量,回收率为96.7％～103.2％。     

α,β-炔醛异构化高立体选择性合成(2E,4E)-十四碳共轭双烯醛

（2E，4E）－共轭双烯是许多天然产物的结构组分[1-5]，由于几何异构体的分离及提纯较困难，因此合成高几何纯度的（2E，4E）共轭双烯衍生物是一个值得探讨的课题．Trost等[1]曾报道了利用α,β-炔酮及炔胺的异构化反应合成（2E，4E）－共轭双烯衍生物的方法．     

SYNTHESES AND MASS SPECTRAL REARRANGEMENTS OF UNSATURATED BIS-SULPHIDES AND BIS-SULPHONES

Abstract

The synthesis of (E)- and (Z)-1.2-bis(p-fluorophenylsulphenyl)stilbenes (2a and 2b) and 1,2-bis(p-fluorophenylsulphonyl)stilbenes (3a and 3b) was carried out and their configurations were consistent with their stereospecific synthesis. The isomeric 1,1-bis(p-fluorophenylsulphenyl)- and 1,1-bis(p-fluorophenylsulphonyl)-2,2-bis(phenyl)ethylenes (8 and 9) were also synthesised and configurations were established by degradative oxidation. Mass spectral rearrangements of all these compounds were examined. Mass spectra of 1,1-bis-sulphide and 1,1-bis-sulphone bears close relationship with those of (E)- and (Z)-isomeric counterparts. Smiles-type rearrangement observed in 1,2-bis-sulphides was absent in 1,2-bis-sulphones. McLafferty-type rearrangement involving hydrogen migration, from aryl group was noticed in both bis-sulphides and bis-sulphones. Vinyl migration to the sulphone oxygen predominates over aryl migration in three isomeric bis-sulphones.     

CONVENTIONAL CHEMICAL AND DIRECT ELECTROCHEMICAL SYNTHESIS OF THE CHELATES OF 2-(N-TOSYLAMINE)BENZALDOXIME AND 2-(N-TOSYLAMINE)BENZAL-O-METHYLOXIME

Abstract

The chemical and direct electrochemical syntheses of copper, cobalt, nickel and zinc chelates of 2-[N-tosylamine)benzaldoxime (L¹H₂) and 2-[N-tosylamine)benzal-O-methyloxime (L²H) are reported. On the basis of the elemental analyse IR and EPR spectra and magnetic properties, dimeric structures ML are suggested from L¹H₂ under the conditions of the chemical synthesis, while electrosynthesis leads to the monomeric complexes M(L¹H)₂. Using L²H as a ligand, only the chelates ML² ₂ are formed, regardless of the method of synthesis.

The copper dimers CuL¹ have antiferromagnetic properties, while the chelates M(L¹H)₂ and ML₂ have normal magnetic moments. In agreement with the magnetic properties and literature data on structures of four-coordinate complexes a tetrahedral structure is assigned.     

ORGANIC PHOSPHORUS COMPOUNDS 91.1 SYNTHESIS AND PROPERTIES OF 1-AMINO-2-ARYLETHYLPHOSPHONIC AND-PHOSPHINIC ACIDS AS WELL AS -PHOSPHINE OXIDES

Abstract

The preparation, physical and spectroscopic properties of l-amino-2-arylethylphosphonic, and -phosphinic acids as well as -phosphine oxides, the phosphorus analogues of phenylalanine are described, and the reactions of l-amino-2-(4-fluorophenyl) ethylphosphonates with acetals, isocyanides, esters, acid anhydrides, activated aromatic nitro- and halogen compounds, and with N-protected alanine are reported. It is shown that several of the 1-amino-2-arylethylphosphonic acids are strong inhibitors of PAL and anthocyanin synthesis and also are quite active botryticides. Among the active compounds were l-amino-2-(4-fluorophenyl)ethylphosphonic acid, 3f, and the methyl-substituted compounds 3k, 31, and 3m. The fluoroderivative 3f was also effective as a seed-dressing agent in barley showing a 100% protection against the fungus Fusarium nivale at 600 ppm.     

二氧化碳和丙烯直接合成甲基丙烯酸CuPW/TiO2催化剂的研究

用溶胶-凝胶法以磷钨酸(TPA)的铜盐溶液水解钛酸四丁酯制备了CuPW/TiO2催化剂。使用ICP、XRD、TG-DTA、IR、TPD-MS和微反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。实验结果表明杂多钨酸盐与TiO2表面通过O2-桥发生键合作用。在623 K下,杂多阴离子仍保持原有的Keggin结构。CO2在Lewis酸位Cu(Ⅱ)和Lewis碱位Cu—O—W的桥氧协同作用下形成卧式吸附态。丙烯以分子吸附态在催化剂上选择吸附。在563 K,1 MPa和空速1 500 h-1的反应条件下,丙烯的摩尔转化率为4.3%,产物MAA(甲基丙烯酸)的选择性为96%。