Comparative studies on the electrochemical and physicochemical behaviour of three different benzimidazole motifs as corrosion inhibitor for mild steel in hydrochloric acid

This paper examines the anticorrosion characteristics of three different benzimidazole derivatives towards mild steel in 0.5?M hydrochloric acid at temperature ranges from 303 to 323?K. The benzimidazole derivatives used for the screening studies are 2-(2-methyl-1H-benzimidazol-1-yl) acethydrazide (EMBAH), 2-(2-ethyl-1H-benzimidazol-1-yl) acethydrazide (EEBAH) and 2-(2-propyl-1H-benzimidazol-1-yl) acethydrazide (EPBAH). The corrosion inhibition was investigated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization studies. The adsorption interaction between metal and inhibitor followed Langmuir adsorption isotherm. The Gibb’s free energy values clarify the spontaneous nature of adsorption process. The temperature dependence of inhibition efficiency was explained by considering thermodynamic parameters of adsorption and kinetic parameters of corrosion. These inhibitors showed good efficiency at lower as well as moderately higher temperatures. Quantum chemical calculations were done using DFT at the B3LYP/6-31G¹ level to study the electronic properties of the molecules for correlating the inhibitive effect and molecular structure.     

MnO2 Nanoparticles as Efficient Oxidant for Ultrasound-Assisted Synthesis of 2-substituted Benzimidazoles under Mild Conditions

In this article, a novel method for synthesis of 2-substituted benzimidazoles using MnO₂ nanoparticles as a convenient oxidant agent in ethanol-water (1:1) as solvent under ultrasound irradiation was demonstrated. In this protocol the desired products were purely obtained in high yields. The main advantages of this research are: mild procedure, simplicity of method, easily work-up, high yields, and short reaction times. The MnO₂ nanoparticles were synthesized through a solid-state reaction route using simple strarting materials. Furthermore, their structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR).     

1,1-双(1H-苯并咪唑-2-基)-1-十三碳烯的合成及其性能

以邻苯二胺和丙二酸为原料,在3 mol/L盐酸催化下合成双(1H-苯并咪唑-2-基)甲烷中间体,然后与月桂醛通过Knoevenagel缩合反应合成了双苯并咪唑衍生物——1,1-双(1H-苯并咪唑-2-基)-1-十三碳烯。利用元素分析、FTIR和~1HNMR对合成产物的结构进行了表征,考察了常规碱催化剂对目标产物收率的影响,并通过UVVis和荧光光谱(FL)测定了目标化合物的光学性能。结果表明:六氢吡啶催化效果最好,产物收率可达76.33%。目标化合物在243、315和361 nm 3处有紫外吸收峰,可有效覆盖日光紫外线UVA和UVB波段;目标化合物溶液在λem=464.5 nm处有蓝紫色荧光,固体薄膜在λ_(em)=476.5 nm处有蓝紫色荧光,荧光量子产率为0.47。标题化合物荧光增白效果与常用荧光增白剂VBL相当。     

Novel aminated benzimidazo[1,2-a]quinolines as potential fluorescent probes for DNA detection: Microwave-assisted synthesis, spectroscopic characterization and crystal structure determination

A synthesis of novel benzimidazo[1,2-a]quinolines, substituted with piperidine, pyrrolidine and piperazine nuclei has been accomplished using an uncatalyzed amination protocol under microwave heating. All compounds were characterized by means of ¹H, ¹³C NMR, IR, UV/Vis and fluorescence spectroscopy. Crystal and molecular structures of 2-chloro- and 2-piperidinyl-benzimidazo[1,2-a]quinoline-6-carbonitrile were determined by X-ray diffractometry. These molecules are essentially planar. Their molecular assembly is characterized by the existence of weak intermolecular hydrogen bonds of C-H⋅⋅⋅N type and π-π aromatic interactions. The π-π aromatic stacking observed in the solid state structures of the 2-chloro- and 2-piperidinyl- derivatives are not analogous. The spectroscopic properties of these amino substituted benzimidazo[1,2-a]quinolines as their hydrochloride salts in the presence of ct-DNA were studied by means of fluorescence spectroscopy. Comparison of binding properties of amino substituted benzimidazo[1,2-a]quinoline hydrochloride salts to ct-DNA revealed significantly enhanced fluorescence emission intensity and thus offer the potential applications as a DNA-specific fluorescent probes.     

Rapid multiresidue and multi-class screening for antibiotics and benzimidazoles in feed by ultra high performance liquid chromatography coupled to tandem mass spectrometry

An analytical strategy was developed for high-throughput screening of multiple antibiotics and two benzimidazoles in feed. Generic sample processing was applied without any purification step. After methanol extraction, the samples were centrifuged, concentrated, and analysed by ultra-high-performance liquid chromatography hyphenated to tandem mass spectrometry in the multiple reaction monitoring mode. Qualitative validation was carried out for more than 50 antibacterials of various classes, including aminocoumarin, amphenicols, beta-lactams, lincosamide, macrolides, diaminopyrimidine, quinolones, sulfonamides, streptogramin, pleuromutilin, polypeptide, quinoxaline, and tetracyclines, and also some benzimidazoles in feed at μg/kg level. Validation was done in accordance with the guidelines laid down in European Commission Decision 2002/657/CE for qualitative screening methods.This convenient, reliable, and sensitive method has been used successfully to monitor antibiotic residues in feeds.     

苯并咪唑类化合物缓蚀性能的量子化学研究

采用量子化学密度泛函理论(DFT)的B3LYP法,基于6-31G(d)和6-311+G(d,P)基纰水平,研究5种苯并咪唑类化合物:苯并咪唑(BIM)、2-丙基苯并咪唑(2-PBIM)、2-戊基苯并眯唑(2-ABIM)、2-己基苯并咪唑(2-HBIM)和2-对氯苄基苯并咪唑(2-CIBBIM)的缓蚀性能与分子结构的关系,讨论量子化学计算结果与缓蚀性能的关系.结果表明,缓蚀剂的缓蚀效率与分子的最稳定质子化形式的最高占据轨道的能量EHOMO、质子化分子的硬度(η)及咪畔环上氮原子的净电荷相关性较好.通过缓蚀剂分子质子化能(PA)及咪唑环上N原子净电荷的分析,可以认为苯并咪唑类缓蚀剂在酸性环境中足以其吡啶N发生质子化形式存在,且通过咪唑环上大π键与金属之间发生作用.     

Dietary intake of pesticides: State of Kuwait total diet study

The State of Kuwait conducted a total diet study (TDS) to determine the dietary intakes of selected pesticides. This paper reports the results of this study. A national food consumption survey was performed and core food lists for different population groups were established representing the total diet of the Kuwaiti population. Food items (table-ready) were purchased/prepared and analysed for their contents of organophosphate/organochlorine carbamate, benzimidazole and phenylurea pesticides according to the US FDA Pesticide Analytical Manual (PAM I). Dietary intakes of these pesticides are presented for 19 population groups, which range from infants to elderly adults. The intakes of selected population groups are compared with representative findings from the US FDA/TDS and data published from other countries. In general, the average daily intakes were well below acceptable limits, but higher than those reported from developed countries.     

Adsorption characteristics of corrosion inhibitors from corrosion rate measurements

Corrosion rate data have been used for the determination of the adsorption parameters of the Frumkin isotherm in the system steel/acid solution/inhibitor. The inhibitors are derivatives of benzimidazole. The maximal amount of adsorbed inhibitor, the interaction parameter a and the equilibrium constant B of the isotherm are found simultaneously by using the SOLVER option of Excel. The statistical analysis of the results shows that this isotherm describes well the adsorption behaviour in the systems studied.