Deep eutectic solvent promoted hydrothiocyanation of alkynoates leading to Z-3-thiocyanatoacrylates

A mild and efficient protocol for the selective construction of Z-3-thiocyanatoacrylates is described. Various alkynoates reacted with KSCN and H₂O by using cheap and recyclable deep eutectic solvent as the catalyst and reaction media to produce the corresponding products in excellent yields with mild reaction conditions and wide substrate scope.     

Efficient Copper(I)‐Catalyzed S‐Arylation of KSCN with Aryl Halides in PEG‐400

A simple and efficient protocol for CuI‐catalyzed C? S bond formation of aryl halides with KSCN to symmetrical diaryl sulfides was reported in PEG‐400 without any other additives. A variety of aryl halides were converted to the corresponding diaryl sulfides in good to excellent yields. The present procedure tolerated a variety of functional groups and the steric hindrance of ortho‐substituents on aryl halides did not affect the outcome.     

用冠醚和硫氰酸钾萃取光度法测定钢铁中微量铌

报道了用双(苯并-18-冠-6)和硫氰酸钾试剂萃取光度测定钢铁中的微量铌,方法的选择性好,灵敏度高,ε_(400nm)=3.85×10~4L·mol~(-1)·cm~(-1),铌在1～20μg/25ml范围内有较好的线性关系,线性回归方程A=0.936C(mg·ml~(-1))-1.425×10~(-3)。     

用勒夏特列原理分析浓度对Fe3+和SCN-显色反应的影响

Fe3+和SCN-的络合反应灵敏、颜色变化明显,考虑中学阶段教学的过渡性,侧重利用勒夏特列原理,从发生氧化还原反应、改变溶液的酸碱性、加入其他配位离子等3个角度分析浓度对该显色反应的影响。     

Pitting of Al and Al–Si alloys in KSCN solutions and the effect of light

The pitting corrosion susceptibility of pure Al and three Al-Si alloys, namely (Al-6%Si), (Al-12%Si) and (Al-18%Si) has been studied in 0.04 M KSCN solution. Measurements were carried out under the effect of various experimental conditions using cyclic polarization, potentiostatic and galvanostatic techniques. In all cases, the potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of a thin film of Al₂O₃ on the anode surface. The passive region is followed by pitting corrosion, at a certain critical potential, pitting potential (E_pit), as a result of breakdown of the passive film by SCN^? anions. Cyclic polarization measurements allowed the determination of the pitting corrosion parameters, namely the pitting potential and the repassivation potential (E_rp). Alloyed Si decreased the passive current (j_pass) and shifted both E_pit and E_rp towards more positive values. Thus alloyed Si suppressed pitting attack. The effect of illumination on passivity and the initiation of pitting corrosion on Al in KSCN solutions was also studied. It is observed that illumination of Al leads to an increase in its pitting corrosion resistance-apparent from j_pass, E_pit, and E_rp measurements in aggressive KSCN solutions.     

通过拓展大学化学实验培养学生探索创新能力——以“硫酸铜中铜含量测定(碘量法)”为例

In one of the experiments of university chemistry laboratory, which is "determination of copper content in copper sulfate (iodometry)", the effect of adding KSCN and the time of adding it were explored at different concentrations of copper sulfate. Results showed that the content of copper was not affected when KSCN was added near the end point or after the introduction of starch, while the content of copper was significantly lower when KSCN was not added or added after KI. This research can be applied in the undergraduate laboratory teaching activity. Under these circumstances, students are divided into different groups according to experimental conditions. Students are guided to compare, analyze and discuss the experimental results. In such a way, students' exploration and innovation spirits are inspired and the teaching effect is improved compared with the traditional book-oriented teaching method.     

Extraktionsspektralphotometrische Spurenbestimmung von Wolfram und Molybd?n in konz. Natriumchlorid-L?sung

Ohne Zusammenfassung

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Extraction-spectrophotometric determination of trace amounts of tungsten and molybdenum in conc. sodium chloride solutions

     

Dynamic symmetry breaking in kscn: A 39K and 14N NMR study

Abstract

The ³⁹K ½ → ?½ NMR angular rotation patterns in KSCN show no symmetry change on going through T_c . We have directly determined with ¹⁴N NMR the SCN head-tail flipping rate. The results show that the absence of a symmetry change in ³⁹K angular rotation patterns is due to the fact that the time scale for the SCN fluctuations is much longer than the characteristic time scale of this experiment. The same is true for the diffuse neutron scattering data where both above and below T_c the SCN groups appear ordered and static and disorder is restricted to domain boundaries. KSCN thus seems to be the first known example where a structural phase transition can be observed in the slow motion and not in the fast motion regime and where a dynamic breaking of the symmetry of the high temperature phase takes place.     

An efficient catalyst-free synthesis of thiiranes from oxiranes using polyethylene glycol as the reaction medium

A catalyst-free, high-yielding conversion of oxiranes into thiiranes has efficiently been carried out by treatment with KSCN or thiourea at room temperature using polyethylene glycol (PEG-400) as the reaction medium.