Cyclopentane-1,3-dione Bis (4-Methylthiosemicarbazone) Monohydrochloride as a Spectrophotometric Reagent for the Determination of Bromate in Perchloric Acid Medium

Abstract

Cyclopentane-1,3-dione bis (4-methylthiosemicarbazone) monohydrochloride produces coloured solutions with bromate ions in perchloric acid medium. The yellow colour obtained (molar absorptivity 1.8×10⁴ 1.mol^?1.cm^?1 at a wavelength of 400 mm) has been used for the spectrophotometric determination of trace amounts of bromate.     

Propane Phosphonic Acid Anhydride: A Mild Reagent for β-Lactam Synthesis

The use of propane phosphonic acid anhydride (T3P) as an acid activating reagent was demonstrated in the syntheses of cis β-lactams from the reactions of a glycine Dane salt and various imines.     

Nitric Acid on Silica Gel: A Useful Nitrating Reagent for Activated Aromatic Compounds

Phenols and arylmethyl ethers are rapidly mononitrated by nitric acid adsorbed in silica gel at room temperature in high yields.     

Studies on the Total Synthesis of Crotocembreneic Acid and Neocrotocembreneic Acid:A Perchloric Acid-induced Lactonization Reaction of Epoxy Ester

Cembranoids, a large family of diterpenoid natural products characterized by the presence of fourteen-membered ring, have been isolated from various marine sources as well as some terrestrial organisms since the 1960's1. Crotocembraneic acid 1 and neocrotocembraneic acid 2 have been isolated from the stem bark of Croton oblongifolius Roxb. (Euphorbiaceae)2. In our studies on the total synthesis of 1 and 2, we find a novel perchloric acid-induced lactonization reaction of epoxy ester 9 (Scheme…     

3,4-Dihydroxybenzoic Acid As A Reagent for the Spectrophotometric Determination of Titanium

Abstract

The reaction between titanium(IV) and 3,4-dihydroxybenzoic acid in aqueous media results in an intensely colored complex which is stable for at least 8h. It allows the spectrophotometric determination of titanium in silicate rocks. The proposed method, in pH 4.0–6.0, shows a molar absorptivity of 1.43.10⁴ L.mole^?1.cm^?1 at 380 nm. Beer's Law is obeyed up to 3.0 μg/mL of titanium(IV). The interference of iron(III) can be eliminated by reduction to iron(II) with hydroxylamine hydrochloride. The method was applied to the determination of titanium in various standard rocks and the results indicated that the accuracy and precision are satisfatory.     

酸性条件下多苯基取代环戊二烯的氧化扩环反应

报道了空气(或氧气)存在的条件下,由高氯酸引发多苯基取代环戊二烯发生新颖的碳-碳键断裂扩环反应,在此反应中,氧原子插入到环戊二烯环中形成相应的六元环吡喃盐类化合物.分别用红外光谱、核磁共振氢谱、碳谱、质谱以及元素分析对所得化合物进行了表征.     

The Mechanism of the Polymerization of Styrene by Perchloric Acid

Abstract

The kinetics of the polymerization of styrene, initiated by anhydrous perchloric acid in carbon tetrachloride solution and in mixtures of methylene chloride and carbon tetrachloride, have been studied by NMR and GLC methods. In carbon tetrachloride the reaction is zeroth order. The kinetics, together with the known effects of dielectric constant and pressure on the reaction rate, suggest that the rate-determining step may be the formation of a carbonium perchlorate ion-pair, associated with neutral molecules of styrene.     

Surface and Subsurface Oxygen on Platinum in a Perchloric Acid Solution

The oxidation of polycrystalline platinum in perchloric acid is studied by cyclic voltammetry at a potential scan rate of 0.1 V s^–1 in various potential cycling ranges. The earlier model for the formation of a barrier layer of strong complexes consisting of subsurface oxygen O_ss, platinum atoms, and anions adsorbed on the latter is shown to correctly describe experimental results on the platinum oxidation in sulfuric and perchloric acids. The regularities in these acids are on the whole similar. A weaker adsorption of perchlorate anions as compared with bisulfate facilitates chemisorption of oxygen at 0.7–0.85 V and hinders exchange by sites Pt O at 0.85–1.35 V. A prolonged potential cycling with a cathodic limit of 0.27 V and low anodic limits leads to the accumulation of surface complexes O_ss–Pt _n –ClO₄, which hinder both the oxygen chemisorption and the exchange Pt O below 1 V. At more positive potentials, the complexes are destroyed and oxygen penetrates into subsurface platinum layers.     

ICP-AES 法间接测定高氯酸二乙基联吡啶中的高氯酸根

研究了ICP－AES法间接测定高氯酸二乙基联吡啶中高氯酸根含量的方法,选择了氯化四苯Lin（TPPCl）与高氯酸根发生沉淀的条件及ICP－AES测定四苯Lin的最佳条件,在氯化四苯Lin过量的情况下,在水中难溶的高氯酸二乙基联吡啶可以定量转化成TPPClO4晶形沉淀,通过测定反应剩余的TPPCl,可计算得到样品中高氯酸根的含量,方法的相对标准偏差0.74%,回收率99.5%-100.6%。同时以TPPCl为沉淀剂,用重量法测定了样品中高氯酸根含量,结果与ICP－AES法一致。     

Chromic Acid Adsorbed on Aluminium Silicate: A New Reagent for Oxidation of Primary Alcohols to Aldehydes

That chromic acid adsorbed on aluminium silicate is a new reagent suitable for oxidation of primary alcohols to corresponding aldehydes is described.     

Rhodamine B Piperazinoacetohydrazine: A Water‐Soluble Spectroscopic Reagent for Pyruvic Acid Labeling

A new water‐soluble reagent, rhodamine B piperazinoacetohydrazine (RBPH), with improved spectroscopic and reaction properties, has been developed and characterized for pyruvic acid labeling. The reagent RBPH is designed and synthesized by using rhodamine B as a spectroscopic unit, and hydrazine as a carbonyl‐specific labeling unit; the two units are connected by a well‐chosen linker of piperazine, which prohibits the formation of the nonfluorescent spirocyclic structure of rhodamine B, thereby keeping the spectroscopic response of the reagent in a stable state. Such a design enables RBPH not only to maintain its excellent spectroscopic properties over a wide pH range, but also to exist as a stable cation with high water solubility. Moreover, the hydrazino group of RBPH is expected to react selectively with carbonyl compounds under mild conditions through the rapid formation of hydrazones. These important features make RBPH of great potential use in the labeling of aldehydes or ketones in various biosystems, and such an application of RBPH as a precolumn derivatizing reagent has been successfully demonstrated on the analysis of pyruvic acid in human serum by high‐performance liquid chromatography with common UV/Vis detection.     

Chromic Acid Adsorbed on Kieselguhr: A New Reagent for the Oxidation of Primary Alcohols to Aldehydes

A new reagent, chromic acid adsorbed on kieselguhr, suitable for the oxidation of primary alcohols to the corresponding aldehydes is described.     

Spectrophotometric Determination of Thorium with Disodium Salt of Arsenazo-III in Perchloric Acid

A rapid and sensitive spectrophotometric method has been developed for the determination of thorium using 0.04% Arsenazo-III in a 2M perchloric acid solution. Absorbance was measured in 1 cm cell and the complex has a sensitive absorption peak at 654 nm. The complex is formed instantly in perchloric acid and remains stable for 45 minutes with constant absorbance. Beer's law is obeyed in the range 1–60 g·g^–1 of thorium concentration with a molar absorptivity at 654 nm = 3.07·10⁵ M^–1·cm^–1 at 24±2°C. The foreign ions interference in thorium determination have been checked. The cations were tested at >60-fold excess of thorium, Mn(II), Fe(III), Co(II) and Ni(II) interfere negatively, whereas only Ce(III) has increased the absorbance. Among the anions, cyanide, phosphate, thiocyanate and acetate at 150-fold excess of thorium cause significant interference. However, thorium can bedetermined in the presence of nitrate, chloride, oxalate, tartrate, ascorbate, thiosulphate and citrate. The method has been applied on certified reference material for thorium determination after extractive separation and the result was found in good agreement with the certified value. The method has been also applied successfully to determine thorium at g·g^–1 level in local ore samples with a precision of ±0.04%.     

甲酸-乙酸-水-氯化钙体系汽液平衡盐效应的研究

本文采用Otsuki-Williams式汽液平衡釜测定了甲酸-乙酸-水体系及甲酸-乙酸-水-氯化钙体系在98658.28Pa下汽液平衡数据。氯化钙的加入量为0.5mol/(kg溶剂)。结合盐效应的作用情况,对相图进行了分析。研究结果表明:氯化钙的加入对体系起了物理化学作用,它与盐溶、盐析现象有关。     

Photopolymerization of Acrylonitrile by Potassium TrisoxalatocobaItate(III) in Aqueous Perchloric Acid

Results of a kinetic study on photopolymerization of acrylonitrile by potassium trisoxalatocobaltate(II1) in aqueous perchloric acid medium (pH = 1) by use of light of 365 nm wavelength at 30 |Mg 0.1°C are presented. All reactions were carried out under completely deaerated conditions. Certain important features of the photopolymerization are described. The rate of polymerization R_p was followed by gravimetric estimation of polymer formed and rate of disappearance of complex - R_c by spectrocolorometric estimation of complex disappearing. R_p was found to be directly proportional to [M]^3/2, k_ε ^1/2, and I^1/2, where P[M], k_ε, and I refer to concentration of acrylonitrile, light absorption fraction of the complex, and light intensity, respectively. -R_c was found to be directly proportional to k_ε and I. A reaction scheme is drawn and kinetic expressions derived on the basis of that scheme are given.     

m-Aminophenylarsonic Acid as a Reagent for the Extraction Preconcentration of Phenol

The azocoupling reaction of phenol with the diazonium salt of m-aminophenylarsonic acid was used for the determination of phenol in water at a level of maximum permissible concentrations. The resulting compound is stable in a wide pH range, which made it possible to develop a procedure for the determination of phenol with the preconcentration of the azo compound by extraction to isobutanol at pH 2 and subsequent back extraction to the aqueous phase at pH 10. The high concentration coefficient of phenol (65) provides for determination of phenol down to 0.9 g/L.     

N-m-Tolyl-o-Methoxybenzohydroxamic Acid (m-T-o-MBHA) as a Specific Reagent for Vanadium

Abstract

A high selective and sensitive spectrophotometric method is described for the determination of traces of vanadium(V) using N-m-tolyl-o-methoxybenzohydroxamic acid. The violet complex extracted into chloroform (λ_max = 545 nm) is stable for several days. As little as 0. 05 μg of vanadium is detectable.