Heteropolyacid-catalyzed synthesis of chloromethyl methyl ether

An efficient (in terms of experiment and time) synthetic procedure for chloromethyl methyl ether (MOM-Cl) is described using heteropolyacids as catalysts.     

High extraction efficiency fiber coated with calix[4] open-chain crown ether for solid-phase microextraction of polar aromatic and aliphatic compounds

The calix[4] open-chain crown ether, 5,11,17,23-tetra-tert-butyl-25,27-di(2-allyloxyethoxyl)-26,28-dihydroxycalix[4]arene was synthesized and used for preparation of solid-phase microextraction (SPME) fibers of enhanced extraction efficiency. The new SPME coating made from calix[4] open-chain crown ether and hydroxyl-terminated silicone oil was developed with the aid of vinyltriethoxylsilane as bridge using sol-gel method and cross-linking technology. The efficiency of the novel fiber in the extraction of polar aromatic and aliphatic compounds, such as phenols, alcohols, and volatile fatty acids, was also investigated. Due to the introduction of the polar open-chain crown ether in calix[4]arene molecules, the calix[4] open-chain crown ether fiber showed much better selectivity and sensitivity to these polar compounds in comparison with calix[4]arene fiber. It also had superior extraction efficiency when compared to commercial poly(dimethylsiloxane)-divinylbenzene and polyacrylate fibers. Parts per billion to parts per trillion level detection limits were achieved for most of the analytes through SPME in conjunction with GC and flame ionization detector. The linear ranges were two to four orders of magnitude, and the RSD values were below 7% for all analytes. The novel fiber was applied to determine volatile alcohols and fatty acids in wine samples. The volatile-free wine prepared in this work was used to assure similar chemical environment for analytes in both calibration solutions and in real wine samples, thus compensating for possible matrix interferences. The established internal standard method using 4-methyl-2-pentanol as internal standard showed satisfactory accuracy and precision.     

取代苯酚中共振增强的分子内氢键

根据晶体结构资料，计算了59个邻位取代苯酚中分子内氢键的几何．在STO－3G水平上计算了一些分子中原子部分电荷．结果表明，酚基氧与苯环上碳之间的键长，酚基上氢原子的部分电荷，酚基所在位置处的苯环环内角与取代苯酚的酸常数pKa均有近似线性关系，当邻位上存在硝基或羰基时，内氢键由于共振而得到显著的增强，据此可说明这一类酚的显著酸性     

Application of particles as pseudo-stationary phases in electrokinetic chromatography

Since the introduction of micelles by Terabe et al. (1984), many different species have been employed as carriers for electrokinetic chromatography. As it is not possible to separate uncharged solutes or ions with equal mobility in capillary electrophoresis, these phases are added to introduce or improve selectivity.

This review surveys the application of particles as pseudo-stationary phases. Up to now only very few applications exist based either on polymer particles for the separation of catechols and primary amines or silica-based material. With these particles separations are shown for phenols, polycyclic aromatic hydrocarbons and naphthalene derivatives. The characteristic properties of particles as pseudo-stationary phases and their benefits as well as their limitations are discussed.     

Facile syntheses of substituted 2,3-dihydrofurans and benzofurans by palladium-catalyzed reactions of propargylic carbonates with nucleophiles

Substituted 2,3-dihydrofurans and benzofurans are synthesized by the palladium-catalyzed reaction of 5-methoxycarbonyloxy-3-pentyn-1-ols and 1-(2-hydroxyphenyl)-3-methoxycarbonyloxy-1-propyne with nucleophiles, respectively. Various substituted propargylic carbonates and nucleophiles are efficiently transformed to their corresponding products. Additionally, a reaction using substrates containing a nucleophilic phenoxy group within the same molecule also produces the corresponding dihydrofuran.     

Sensitive measurement of ultratrace phenols in natural water by purge-and-trap with in situ acetylation coupled with gas chromatography-mass spectrometry

A novel purge-and-trap method coupled with gas chromatography-mass spectrometry (GC-MS) is developed for the analysis of trace and ultratrace phenols based on their derivatization with acetic anhydride. Parameters affecting the extraction efficiency, such as purge temperature, concentration of sodium chloride, purge time, and volume of derivatization reagent, were investigated. The optimized conditions were addition of 150 μL acetic anhydride, purge time of 25 min at the purge temperature of 60 °C with 30% NaCl. The linear range was 0.2–100 μg L⁻¹ for phenols. The limits of detection (LODs) ranged from 0.08 to 0.15 μg L⁻¹ and the relative standard deviations (RSDs) for most of the phenols at the 10 μg L⁻¹level were below 10%. Natural water samples collected from a pool were successfully analyzed using the proposed method. The recovery of spiked water samples was 72.9–84.2%.     

酚类化合物在二氧化锡微粒修饰碳纤维电极上的氧化及检测

采用金属有机化学气相沉积技术制备了SnO2 修饰碳纤维微柱电极 ,讨论了电极的表面结构和稳定性 ,并利用循环伏安法分析了酚类化合物在电极上的电化学行为。该电极对酚类化合物有明显的电催化活性 ,并能防止酚类物质在碳纤维电极表面的电聚合。以 3 氯苯酚为测试物 ,其检测的线性浓度范围为 2× 10 -6～ 1.2× 10 -5mol/L     

载溴树脂溴化酚类的研究

用简便方法制备得载溴树脂并用于酚类的溴化,当采用不同摩尔比的载溴树脂时,有选择地得到一溴、二溴及三溴代物,并有较高的产率,同时该树脂具有良好的稳定性。     

Application of a quick,easy, cheap,effective, rugged and safe-based method for the simultaneous extraction of chlorophenols,alkylphenols, nitrophenols and cresols in agricultural soils,analyzed by using gas chromatography–triple quadrupole-mass spectrometry/mass spectrometry

Due to the different physico-chemical properties of phenols, the development of a methodology for the simultaneous extraction and determination of phenolic compounds belonging to several families, such as chlorophenols (CPs), alkylphenols (APs), nitrophenols (NTPs) and cresols is difficult. This study shows the development and validation of a method for the analysis of 13 phenolic compounds (including CPs, APs, NTPs and cresols) in agricultural soils. For this purpose, a quick, easy, cheap, effective, rugged and safe (QuEChERS)-based procedure was developed, validated and applied to the analysis of real samples. A derivatization step prior to the final determination by gas chromatography (GC) coupled to a triple quadrupole analyzer operating in tandem mass spectrometry (QqQ-MS/MS) was performed by using acetic acid anhydride (AAA) and pyridine (Py). The optimized procedure was validated, obtaining average extraction recoveries in the range 69–103% (10 μg kg⁻¹), 65–98% (50 μg kg⁻¹), 76–112% (100 μg kg⁻¹) and 76–112% (300 μg kg⁻¹), with precision values (expressed as relative standard deviation, RSD) ≤ 22% (except for 4-chlorophenol) involving intra-day and inter-day studies. Furthermore, 15 real soil samples were analyzed by the proposed method in order to assess its applicability. Some phenolic compounds (e.g. 2,4,6-trichlorophenol or 4-tert-octylphenol) were found in the samples at trace levels (<10 μg kg⁻¹).     

光致噻吨酮与胺类、酚类、醇类的电子转移和氢转移反应

利用激光闪光光解方法研究了一系列胺类、酚类、醇类在脱氧乙腈中猝灭噻吨酮(TX)三重态的反应,得到了相应的瞬态吸收光谱和猝灭速率常数(kq).通过对光谱演变特性的分析,推断出三重态噻吨酮与不含有活泼氢的胺发生了电子转移反应,与含有活泼氢的胺发生了电子-质子转移反应.三重态噻吨酮与酚类、醇类反应中观察到噻吨酮加氢自由基的生成,据此推断出三重态噻吨酮与酚类、醇类发生了氢转移反应.胺类的猝灭速率常数随着反应自由能变(ΔG)的增大而减小,说明电子转移影响了噻吨酮三重态的猝灭.酚类的猝灭速率常数先随ΔG增大而减小,后随酚阳离子的酸性增强逐渐增大,可能是猝灭过程中电子转移影响减弱的同时氢转移影响逐渐增强.醇类的猝灭速率常数随着醇的α-C—H键能的增大而减小,说明α-C—H键能是影响噻吨酮三重态猝灭的关键因素.比较以前研究的胺类、酚类、醇类与三重态呫吨酮(XT)、芴酮(FL)反应的结果可知,由于分子结构差异性的影响,相关的猝灭速率常数按照呫吨酮、噻吨酮、芴酮的顺序逐渐减小.