Oxidative conversion of thiourea and N-substituted thioureas into formamidine disulfides with acidified chloramine-T: a kinetic and mechanistic approach

The kinetics of oxidation of thiourea and N-substituted thioureas namely: N-methylthiourea, N-allylthiourea N-phenylthiourea and N-tolylthiourea to the corresponding formamidine disulfides by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in the presence of HClO₄ has been investigated at 278 K. The reactions follow identical kinetics for all thioureas, being first order each with respect to [CAT]_o, [Thiourea]_o and [H⁺]. Ionic strength of the medium and addition of p-toluenesulfonamide or halide ions have negligible influence on the rate. The solvent isotope effect has been studied using D₂O in the case of the oxidation of thiourea. Decrease in the dielectric constant of the medium by adding methanol decreases the rate. The reactions were studied at different temperatures, and the composite activation parameters have been computed. An isokinetic relationship was observed with β=314 K, indicating that enthalpy factors control the reaction rate. Under comparable experimental conditions, the rate of oxidation of thioureas increases in the order: N-allylthiourea>N-phenylthiourea>N-methylthiourea>thiourea>N-tolylthiourea. A mechanism involving the interaction of conjugate acid (CH₃C₆H₄SO₂NHCl) and substrate giving an intermediate complex, in a slow step, has been suggested. The derived rate law is in agreement with the observed kinetics.     

Synthesis of Soluble,Curable, and Thermally Stable Aromatic Polyamides Bearing Thiourea and Pendent 4-Pyridylformylimino Groups

A new aromatic dicarboxylic acid monomer 4-pyridylformylimino-N-(phenyl,2′,5′ – dicarboxylic acid) (PPDC) containing pyridine and azomethine units was synthesized through a simple one-step condensation reaction between 2-aminoterephthalic acid and 4-pyridinecarboxaldehyde. A series of new polyamides was prepared through the direct one-pot phosphorylation polycondensation of PPDC with simple aromatic commercial diamines and diamines bearing phenylthiourea groups. The polyamides were characterized by FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. Thermal stability of the polymers was evaluated using thermogravimetric analysis. The polyamides with inherent viscosities in the range of 0.30–0.51 dL/g showed an outstanding solubility in various solvents such as 1-methyl-2-pyrrolidone (NMP), dimethly sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimetylacetamide (DMAc), and pyridine. The cured polyamides displayed significantly higher thermal stability than the uncured polyamides. The conductivity of the polyamides, when blended with 20% by weight of doped polyanilines, was in the range 3.09–4.21 × 10^?3 S cm^?1.     

还原染料的还原体系探讨

本文详细介绍了还原染料还原工艺中保险粉及其他传统还原体系的利弊,阐述了当前还原染料新型还原技术的特点及需要解决的问题。     

硫脲浸金技术研究现状

针对氰化浸金存在环境不友好、生产周期长的不足,诸多非氰浸金方法得以研究和应用。综合阐述了硫脲浸金技术的研究现状,主要有酸性硫脲浸金体系、碱性硫脲浸金体系、硫脲浸出贵液回收等,展望了今后的研究重点。     

一锅法合成6-甲基-2-硫脲嘧啶的工艺研究

采用了一锅法合成工艺,以乙酰乙酸乙酯和硫脲为起始原料,经过脱水、脱醇缩合成环得到6-甲基-2-硫脲嘧啶,其结构经1H NMR、IR和MS表征。最佳反应条件为:硫脲90 mmol,n(硫脲):n(乙酰乙酸乙酯):n(氢氧化钾)=1:2.30:2.32时,产物收率为96.64%。     

Sensory Arrays of Covalently Functionalized Single‐Walled Carbon Nanotubes for Explosive Detection

Chemiresistive sensor arrays for cyclohexanone and nitromethane are fabricated using single‐walled carbon nanotubes (SWCNTs) that are covalently functionalized with urea, thiourea, and squaramide containing selector units. Based on initial sensing results and ¹H NMR binding studies, the most promising selectors are chosen and further optimized. These optimized selectors are attached to SWCNTs and simultaneously tested in a sensor array. The sensors show a very high level of reproducibility between measurements with the same sensor and across different sensors of the same type. Furthermore, the sensors show promising long‐term stability, which renders them suitable for practical applications.     

硫脲络合重量法测定镍钛铂合金中铂

镍钛铂合金中铂含量与合金材料的理化性能有着密切的联系,也是重要的交易指标之一。采用盐酸-硝酸混合酸以及硫酸分解样品,在加热至冒硫酸烟时,铂-硫脲络合物形成硫化物沉淀,从而与其他元素分离,经过滤,灼烧,恒重,计算得到铂含量;使用电感耦合等离子体原子发射光谱法(ICP-AES)测定滤液中铂含量,其含量很低,对样品中铂含量没有贡献,无需补差,即铂已经完全沉淀。试验结果表明,盐酸与硝酸体积比为5∶1时样品溶解速度最快;硫酸(1+1)加入总量为80mL,硫脲用量为2.0g时,铂可以沉淀完全并易于过滤。按照实验方法测定2个镍钛铂样品中铂,结果的相对标准偏差(RSD,n=10)分别为0.17%和0.12%;与氯铂酸铵重量法进行比对,并采用F检验和t检验,结果表明两种方法在显著性水平为0.10时没有显著性差异。加标回收率在99%~102%之间。     

非氰提金技术研究进展

随着难处理金矿的占比不断增加以及人们对环保问题的日益重视,氰化法受到了技术和环保两方面的制约,非氰方法成为金、银提取的必然趋势。非氰方法包括湿法工艺和火法工艺两大类。系统介绍了湿法非氰方法中卤素法、硫脲法、硫代硫酸盐法、硫氰酸盐法和环保提金剂的原理及发展状况;火法非氰方法主要介绍了具代表性的高温氯化焙烧工艺和造锍捕金工艺,其适用对象分别为铁含量高的含金物料和含砷、硫、碳等难处理金精矿。通过综合分析得出贵金属提取的重要趋势是火法—湿法工艺结合,即先通过火法充分富集贵金属,再利用湿法工艺高效回收。     

化学镀Ni-P-S阴极的析氢性能

用化学镀的方法得到Ni-P-S电极,研究镀液中添加不同硫脲量对电极析氢活性的影响,电极在碱性溶液中具有较高的析氢活性,通过稳态极化曲线测量,得到在1mol／L NaOH溶液中不同实验条件下电极的析氢反应动力学参数。     

硫脲冻融循环法分离硫酸铅−黄钠铁矾共沉淀物中的铅

采用硫脲冻融循环法分离硫酸铅?黄钠铁矾共沉淀物中的铅.研究结果表明,在硫脲冻融循环过程中,共沉淀物中混杂的硫酸铅逐渐在黄钠铁矾表面聚集,同时通过冷冻浓缩作用促进硫酸铅与硫脲反应,形成硫脲铅(Pb-tu)新物相.随着冻融循环次数的增加,黄钠铁矾周围的硫酸铅不断转化为Pb-tu,直至反应完全.12次冻融循环后,黄钠铁矾和P...