2-(2′-羟苯基)苯并噁唑氨基衍生物电子结构和光谱性质的理论研究

采用量子化学方法优化了间位和对位2-(2′-羟苯基)苯并噁唑氨基取代衍生物(4-AHBO和5-AHBO)基态的第一单重激发态所有可能的稳定构型, 分析了这些异构体在不同溶剂中的相对稳定性. 利用含时密度泛函理论(TDDFT)的不同泛函, 计算了4-AHBO和5-AHBO各异构体在溶剂中的吸收与发射光谱, 考察了它们的电子结构和光谱特征. 结果表明, 4-AHBO(5-AHBO)的双荧光不是由同一种异构体发射的, 而是来源于不同异构体的发射: 长波区的荧光由酮式构型发射, 短波区的发射则可能由四种醇式异构体共同产生. 另外, 也解释了5-AHBO在质子溶剂中光谱异常的原因, 分析了不同氨基取代位和溶剂极性的变化对各异构体构型、光谱性质及电子结构的影响. 理论预测的光谱与实验结果一致.     

亚硝基化合物与甲醛的反应机理和溶剂效应的理论研究

采用密度泛函方法B3LYP/6-311++G(d,p)研究了亚硝基苯C₆H₅-NO和2-甲基-2-亚硝基丙烷(CH₃)₃C-NO与甲醛分别在气相和溶剂中的反应机理. 在气相中均找到两条反应通道, 即协同机理和分步机理, 均生成实验产物氧肟酸, 而且分步机理均为优势通道; 除2-甲基-2-亚硝基丙烷的反应没有协同途径外, 在溶剂中反应机理与气相中的类似. 采用导电极化连续介质模型分别研究了在乙腈与水溶液中反应的溶剂化效应, 发现这些溶剂可降低反应的活化能, 但降低的程度比较小, 反应速率变化不大.     

Biomass Valorization Using Natural Deep Eutectic Solvents: What’s New in France?

With the growing interest in more environmentally friendly solvents and processes, the introduction of Natural Deep Eutectic Solvents (NaDES) as low cost, non-toxic and biodegradable solvents represent a new opportunity for green and sustainable chemistry. Thanks to their remarkable advantages, NaDES are now arousing growing interest in many fields of research such as food, health, cosmetics and biofuels. Around the world, NaDES are seen as a promising alternative to commonly used petrochemical solvents. The objective of this review is to draw up a panorama of the existing skills on NaDES in French laboratories and industries for the valuation of natural products. This review therefore focuses on current applications, skills and perspectives, in order to analyze the place of French research in the use of NaDES for the valorization of biomass since 2015.     

Solvent Dependence of Photophysical and Photochemical Behaviors of Thioxanthen-9-one

The photophysical and photochemical behaviors of thioxanthen-9-one (TX) in different solvents have been studied using nanosecond transient absorption spectroscopy. A unique absorption of the triplet state \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} is observed, which involves two components, \begin{document}$ ^3 $\end{document}n\begin{document}$ \pi $\end{document}\begin{document}$ ^* $\end{document} and \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} states. The \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} component contributes more to the \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} when increasing the solvent polarity. The self-quenching rate constant \begin{document}$ k_{ \rm{sq}} $\end{document} of \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} is decreased in the order of CH\begin{document}$ _3 $\end{document}CN, CH\begin{document}$ _3 $\end{document}CN/CH\begin{document}$ _3 $\end{document}OH (1:1), and CH\begin{document}$ _3 $\end{document}CN/H\begin{document}$ _2 $\end{document}O (1:1), which might be caused by the exciplex formed from hydrogen bond interaction. In the presence of diphenylamine (DPA), the quenching of \begin{document}$ ^3 $\end{document}TX\begin{document}$ ^* $\end{document} happens efficiently via electron transfer, producing the TX\begin{document}$ ^\cdot $\end{document}\begin{document}$ ^- $\end{document} anion and DPA\begin{document}$ ^{\cdot} $\end{document}\begin{document}$ ^+ $\end{document} cation radicals. Because of insignificant solvent effects on the electron transfer, the electron affinity of the \begin{document}$ ^3 $\end{document}n\begin{document}$ \pi $\end{document}\begin{document}$ ^* $\end{document} state is proved to be approximately equal to that of the \begin{document}$ ^3 $\end{document}\begin{document}$ \pi\pi^* $\end{document} state. However, a solvent dependence is found in the dynamic decay of TX\begin{document}$^{{ \cdot ^ - }}$\end{document} anion radical. In the strongly acid aqueous acetonitrile (pH = 3.0), a dynamic equilibrium between protonated and unprotonated TX is definitely observed. Once photolysis, \begin{document}$ ^3 $\end{document}TXH\begin{document}$ ^{+*} $\end{document} is produced, which contributes to the new band at 520 nm.     

气相色谱法测定茶叶中克螨特、哒螨酮残留量

提出了测定茶叶中克螨特、哒螨酮残留的气相色谱方法.试样经丙酮提取,正己烷反萃取,弗罗里硅土柱进行净化,用不同极性的淋洗剂分段收集.以气相色谱-电子捕获检测器(GCECD)方式测定哒螨酮,气相色谱-火焰光度检测器(硫滤光片)[GC-FPD(S)]方式测定克螨特,外标法定量.试验表明:试样中加入0.25～10 mg·kg-1浓度水平的克螨特,回收率为84%～102%,方法的测定下限为0.25 mg·kg-,同一样品中6次测定克螨特残留量的相对标准偏差小于5%.试样中加入0.01～0.5 mg·kg-1浓度水平的哒螨酮,回收率为90%～103%,方法测定下限为0.01 mg·kg-1,同一样品中6次测定哒螨酮残留量的相对标准偏差小于5%.     

用气-质联用技术检测葱、蒜、韭菜中多种农药残留量时试样预处理方法

采用气相色谱及质谱联用技术,测定葱、蒜及韭菜等蔬菜中多种农药残留量时,在粉碎试样之前,用磷酸或微波加热处理试样,可使蒜酶钝化并消除其基体干扰。试验结果显示,或用磷酸处理,或经微波加热处理,均能有效消除高背景的干扰。试样在粉碎前经磷酸预处理,在所测定的75种农药中有90％以上农药的回收率达到70％～120％之间。     

静态顶空/气相色谱-质谱联用快速测定茶粉中残留溶剂

在基质改性剂H2O,平衡温度55℃,进样针温度60℃,传输线温度65℃,平衡加热时间30min,顶空气体进样量0.2mL等顶空取样条件下,建立了静态顶空取样,气-质联用技术快速测定茶粉中残留溶剂乙酸乙酯、氯仿的方法。结果表明该方法简单快速、准确度高、重复性好。     

气相色谱法测定土壤中有机氯杀虫剂

建立了利用加速溶剂萃取和GC-ECD联用技术,对土壤中六六六、滴滴涕、艾氏剂、狄氏剂、硫丹Ⅰ、硫丹Ⅱ、硫丹硫酸盐内氯甲桥奈、内氯甲桥奈醋醛、七氯、环氧七氯17有机农药进行了分析,通过对回收率、重现性及精密度的测定,其实验具有操作简便,时间短,应用范围广的优点.     

溶剂浮选-紫外分光光度法测定厚朴中总厚朴酚

建立了一种测定厚朴中总厚朴酚的新方法,即采用溶剂浮选法分离富集厚朴中的总厚朴酚,用紫外分光光度法测定其含量。考察了浮选溶剂、试液pH、氮气流速、浮选时间及电解质NaCl等因素对浮选效果的影响,优选出最佳浮选条件。采用所述方法对不同产地厚朴样品中总厚朴酚含量进行测定,样品加标回收率为94.9%-100.8%,RSD为2.8-4.1%。     

Diels-Alder Addition of Dicyclopentadiene with Cyclopentadiene in Polar Solvents

Diels-Alder addition of dicyclopentadiene and cyclopentadiene in polar solvents has been studied to produce tricyclopentadiene（TCPD） that is a potential high-density fuel precursor. GC and MS analysis shows that the adducts contain two isomers, namely exo- and endo-TCPD. Theoretical simulation shows that although the transition state of endo-TCPD has a lower activation energy, exo-TCPD is thermodynamically preferred. Polar solvents can accelerate the reaction rate and improve the exo/endo ratio of TCPD because the transition state of exo-TCPD has a higher polarity than that of endo-TCPD. The solvent effect follows the order of polarity： benzyl methanol〉cyclohexanone〉toluene. The conversion rises when the temperature ranges from 120 to 150 ℃, but the selectivity of TCPD slightly decreases. Increasing the pressure can improve the conversion but the exo/endo ratio of TCPD is unchanged. The apparent kinetics in different solvents was determined via nonlinear regression. The activation energies are 99.47, 101.15, and 107.32 kJ/mol for benzyl methanol, cyclohexanone, and toluene, respectively. The optimal reaction conditions are as follows： benzyl methanol as solvent, temperature 150 ℃, and pressure 900 kPa. After an 11-hour reaction, a conversion of 58.0%, a TCPD selectivity of 95.7%, and an exo/endo ratio of 1/5.3 has been obtained.