基团电负性与含氧有机物的标准生成热

本文利用作者提出的基团电负性,建立了一个计算含氧有机物标准生成热的简单方法: △fH°(RZ)=△fH°(CH_3Z)-(0.48 n~(1/2)+17.18)x_G-20.13n+69.71式中,△fH°(RZ)和△fH°(CH_3Z)分别为含氧有机物RZ和CH_3Z的标准生成热;Z-OE_e、OM_e、OH、COCH_3、CHO、CO_2H、CO_2Me、CO_2Et.CONH_2;x_G为基团Z的电负性;n是直链烷基R中的碳原子个数,48个可比较值的平均偏差为0.3kCal/mol。     

(1,3,5-C3P3H3)M与(1,3,5-C3P3H3)2M (M=Ti,V, Cr)配合物的结构与芳香性

运用密度泛函理论研究了(1,3,5-C3P3H3)M和(1,3,5-C3P3H3)2M (M=Ti,V,Cr)的结构、键合能以及芳香性.结果表明:低自旋的(1,3,5-C3P3H3)M和(1,3,5-C3P3H3)2M基态结构分别具有C3v和D3h对称性.金属与配体间为共价作用,二者之间存在σ、π和σ三种成键方式.V的三明治配合物的解离方式与Ti和Cr的三明治配合物不同,前者为分步解离,后两者则为一步解离.其中(1,3,5-C3P3H3)2Cr(D3h)的第一解离能最大,配合物最稳定.这些三明治和半三明治配合物都具有中心芳香性、内芳香性和外芳香性,且中心芳香性均大于自由配体(1,3,5-C3P3H3)的中心芳香性,芳香性主要贡献来源于π键和金属原子的孤对电子.内芳香性按照Ti、V、Cr的顺序依次增大,且内芳香性明显要大于外芳香性.高自旋的半三明治(1,3,5-C3P3H3)Ti(C3,5A1)与单重态(1,3,5-C3P3H3)Ti (C3v,1A1)相比,配体的变形性增大,稳定性增加,且C平面中心芳香性和内芳香性均增大,但P平面的中心芳香性却降低.     

使用反应图评价高师学生有机物转化知识结构

以高师本科化学专业二年级95名学生为教学对象,探讨反应图作为学生有机物转化知识结构评价工具的可行性。研究发现:(1)学生制作的反应图能够定量反映学生的有机物转化知识结构;(2)不同有机化学学业水平的学生群体的反应图、有机物转化知识结构存在差异;(3)学生的反应图总分与期中考试成绩有显著的弱相关。     

2,4-二硝基氯苯碱性水解胶团催化的活化能

研究了阳离子表面活性剂氯化十六烷基吡啶(CPC)和十六烷基三甲基氯化铵(CTAC)胶团对2,4-二硝基氯苯(DNCB)碱性水解的催化作用和小分子极性有机物丁醇的加入对该反应的影响,计算了反应活化能.结果表明:(1)CPC和CTAC胶团对DNCB碱性水解都有明显的催化作用;(2)加入少量叔丁醇略有利于提高催化效果;(3)在CPC和CTAC胶团溶液中DNCB碱性水解反应的活化能约为49kJ/mol,比纯水中的91kJ/mol低得多,说明反应机制可能存在差异.     

环丙烯基自由基H-F力的abinitio研究

环丙烯基自由基是我们熟知的最小环状化合物。人们用不同的理论方法对它进行了预测。一般认为平面构型(D_(3h)对称性)要经受Jahn-Teller畸变以消除π轨道的简并性,畸变过程如图1所示。我们研究了此类三元环自由基引起的键的“弯曲效应”,以便对这类“张力”分子的成键特性及Jahn-Teller畸变、芳香性等给出某些理论信息,探讨其理论计算结果所能阐明的问题。     

用分子形貌理论探讨杂环化合物的键长、极化率和芳香性

本文使用MELD精密从头计算中的CISD/3-21+G(d,p)方法,计算杂环化合物的单电子所受到的作用势(PAEM)和分子形貌(MF),探讨这些分子的化学键的单电子势垒(Dpb)与各自相应的化学键键长的关系,得出化学键的单电子势垒可以用来表征化学键的强弱;探讨这些分子的杂环内的单电子势垒(Dpr)与分子极化率的关系,可知该势垒可以描述分子的变形性;绘出杂环化合物的分子形貌,计算垂直于分子平面方向上的边界轮廓界面的电子密度,探讨该分子界面电子密度的均匀度与杂环化合物芳香性的关系,进而为杂环芳香化合物的芳香性提出一个定量的标度.     

纳滤膜在水处理中的最新应用进展

纳滤膜(NF)是新的分离膜品种,对溶质的截留性能介于超滤膜(UF)和反渗透膜(RO)之间。纳滤膜的特性是表面带有电荷并具有纳米级的微孔,能够去除高价离子和分子量大于200的溶解性的有机物。特殊的分离效果使纳滤技术单独或者和其它技术联用应用于水处理领域,主要包括:(1)饮用水制备和深度净化;(2)海水淡化;(3)废水处理,例如生活污水、垃圾渗滤液等等。本文综述了纳滤技术在上述水处理领域中的应用进展及现存问题。     

三维荧光光谱法表征污水中溶解性有机污染物

采用三维荧光光谱法研究了生活污水中溶解性有机物的荧光特性.基于对污水中腐殖酸类、蛋白质类、表面活性剂类、植物油类等有机物三维荧光特性研究结果,提出了表征污水中有机物种类、组成和含量的三维特征荧光参数:(1)特征荧光强度(Fex/em)表征污水中某一类溶解性有机物含量;(2)特征荧光强度综合指标(各类有机物的特征荧光强度之和,∑Fex/em)表示有机物的综合含量;(3)Fex/em/∑Fex/em表示不同种类有机物所占的比值.与传统有机物综合指标相比,三维特征荧光参数信息丰富、测定迅速、灵敏度高,能够方便地实现对水质的实时在线监测,从而更好地指导污水处理工艺运行、管理和控制,保证处理效果.     

过渡金属团簇Nbn、Con(n≤4)和NbxCoy(x+y≤8)的芳香性

采用杂化密度泛函(DFT)方法优化了过渡金属纯团簇Nbn, Con(n≤4)和二元铌钴团簇NbxCoy(x+y≤8)的结构, 并计算了较稳定结构的NICS(核独立化学位移)值, 分析这些过渡金属团簇的成键情况, 讨论不同轨道对各过渡金属团簇芳香性的贡献, 发现在过渡金属团簇中, 除了具有s、p轨道贡献的σ、π芳香性外, 很重要的地d轨道的参与而形成的δ芳香性.     

过渡金属团簇Nbn、Con（n≤4）和NbxCoy（x＋y≤8）的芳香性

采用杂化密度泛函(DFF)方法优化了过渡金属纯团簇Nbn,Con(n≤4)和二元铌钴团簇NbxCoy(x+y≤8)的结构.并计算了较稳定结构的NICS(核独立化学位移)值,分析这些过渡金属团簇的成键情况,讨论不同轨道对各过渡金属团簇芳香性的贡献,发现在过渡金属团簇中,除了具有s,p轨道贡献的σ、π芳香性外,很重要的地d轨道的参与而形成的δ芳香性.     

Conductivity of island metal films covered with organic molecules

Experimental data were obtained on the effect of adsorbed organic molecules (naphthalene, stearone, benzene, xylene, aluminum oxyquinoline and mixtures of some aliphatic compounds) on the conductivity of gold island films. Nanoisland structures were realized which exhibit non-linear conduction current–voltage characteristics and a sharp switching effect in the presence of adsorbed organics. The conditions for the occurrence of the voltage-controlled negative resistance in such nanocomposite systems are discussed. Some data are also given on electroluminescence of the nanocomposites. Two theoretical models are suggested to describe the conduction current–voltage characteristics of organic molecular structures under various conditions.     

镧系收缩效应对稀土-煤相互作用的影响及煤中有机态稀土的赋存形式研究

通过酸洗脱灰及腐殖酸提取等方法对伊敏褐煤进行处理,并应用ICP-MS对处理前后的样品进行了稀土元素测定。在对脱灰前后稀土元素与灰分和C、H、O等有机组成元素的相关性以及稀土元素在腐殖酸中的赋存特征分析的基础上,认为煤中稀土元素-有机质相互作用受煤化作用过程中的脱氧、脱氢和增碳作用控制。稀土与煤中各类官能团相互作用形成四类有机态稀土元素复合物,第一类是与被烷基侧链高度取代的芳香结构单元形成的复合物;第二类是与氢化芳香结构单元形成的复合物;第三类是与低取代度的芳香结构单元形成的复合物;第四类是与含氧官能团作用形成的复合物,后两类的稳定性差。这些有机态稀土元素复合物的稳定性在总体受镧系收缩效应控制的基础上,还受稀土元素化学价态的影响;重稀土与有机质形成的有机态稀土元素复合物的稳定性大于轻稀土。轻稀土在原煤中和腐殖酸的结合不稳定,且具有与镧系收缩相反的效应;轻稀土在脱灰煤中和腐殖酸的结合,与中稀土、重稀土在原煤和脱灰煤中腐殖酸结合规律相同,都体现了良好的镧系收缩效应。     

Trifluoromethanesulfonic acid in organic synthesis

The review analyzes data published in the past decade on the use of trifluoromethanesulfonic acid (triflic acid, CF₃SO₃H, TfOH) in organic synthesis, in particular in electrophilic aromatic substitution (Friedel–Crafts) reactions, formation of carbon–carbon and carbon–heteroatom bonds, isomerizations, syntheses of carboand heterocyclic structures, and other reactions, as well as in natural and organometallic compounds chemistry. The high protonating power and low nucleophilicity makes trifluoromethanesulfonic acid capable of generating from organic molecules cationic species which can be detected by spectral methods (NMR, IR spectroscopy, etc.), and their transformations can be studied. Experimental simplicity and efficiency of reactions promoted by trifluoromethanesulfonic acid make it a convenient reagent for the synthesis of new organic compounds.     

Understanding otolith biomineralization processes: new insights into microscale spatial distribution of organic and mineral fractions from Raman microspectrometry

It is generally accepted that the formation of otolith microstructures (L- and D-zones) and in particular the organic and mineral fractions vary on a daily basis. Raman microspectrometry provides a nondestructive technique that can be used to provide structural information on organic and mineral compounds. We applied it to thin otolith sections of hake in order to address the following issues: (1) the simultaneous characterization of variations in the organic and mineral fractions both in the core area and along successive otolith microstructures; (2) elucidation of significant differences between these fractions; (3) quantification of the effects of etching and staining protocols on otolith structures. The primordium appeared as a punctual area depicting higher luminescence and greater concentrations in organic compounds containing CH groups. Sulcus side showed similar composition suggesting that the contact of the otolith with the macula and its orientation in otosac occur rapidly (about 10 days). The characterization of L- and D-zones in the opaque zones indicated that both structures contained organic and aragonitic fractions with cyclic and synchronous variations. Contrary to the results obtained after EDTA etching, L-zones depicted greater concentrations in organic compounds containing CH groups, whereas D-zones appear richer in aragonite. This organic fraction seemed to be revealed by Mutvei’s staining and was affected by EDTA etching which suggests that it corresponds to the soluble fraction of organic matrix. Such results indicate that L- and D-zones differ in their respective organic constituents. Raman microspectrometry thus appears as a powerful technique to acquire quantitative information that is required for a better understanding of otolith biomineralization. Figure Raman microspectrometry is a powerful technique for studying otolith biomineralization     

Convenient Synthesis of 1-Thiohydroxypyrene by Newman-Kwart Rearrangement

1-Thiohydroxypyrene(1) and its two intermediates, 1-pyrenyl-O-thiocarbamate(2) and 1-pyrenyl-S-thio- carbamate(3), were synthesized using 1-hydroxypyrene as the starting material. The key synthetic step is Newman-Kwart rearrangement. The results indicate that the Newman-Kwart rearrangement is more effective in suitable solvent than conventional method based on pure organic compound. The structures of compounds 1―3 were characterized by FTIR, NMR, GC-MS and elementary analysis. The crystal structures of two new compounds(2 and 3) were determined by single crystal X-ray diffraction analysis. The whole synthetic process is simple, mild and with high yield.     

Structures of substituted di-aryl-1,3,4-oxadiazole derivatives: 2,5-bis(pyridyl)- and 2,5-bis(aminophenyl)-substitution

Crystal structures of four different di-aryl-1,3,4-oxadiazole compounds (aryl = 2-pyridyl-, 3-pyridyl-, 2-aminophenyl-, 3-aminophenyl-) are determined. Crystallization of di(2-pyridyl)-1,3,4-oxadiazole yielded monoclinic and triclinic polymorphs. The structures are characterized by the occurrence of π–π interactions. Additionally, in case of the aminophenyl compounds intra- as well as intermolecular hydrogen bonds are found that influence the packing motif as well. Since these molecules are often used as ligands in metal–organic complexes similarities and differences of the molecular conformation between the molecules in the pure crystals and that of the ligands in the complexes are discussed.     

A simple accurate model for prediction of deflagration temperature of energetic compounds

A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO₂, –ONO₂, or –CNO₂ groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol.     

X-ray diffraction investigation of siloxanes. III. Structure and configuration of cyclic tetra-and pentasiloxanes bearing different organic substituents at silicon atoms

Single crystal X-ray diffraction is applied to elucidate the structures of six tetra-and one penta-siloxane compounds differing in the nature and position of silicon-sitting organic substituents (Me — methyl, Ph — phenyl, mPh — methoxyphenyl, 2mPh — dimethoxyphenyl, 3mPh — trimethoxypehnyl, and C₄H₆N — butironitrile). Charge states of atoms in the siloxane molecules are calculated, and the effect of oxygen-containing radicals on the Si-O bond lengths and Si-O-Si bond angles affecting the configurations of the tetra-and pentasiloxane cycles is shown.     

A survey of interactions in crystal structures of pyrazine‐based compounds

The important role of pyrazine (pz) and its derivatives in fields such as biochemistry and pharmacology, as well as in the study of magnetic properties, is surveyed. Recognition of these properties without extensive investigations into their structural properties is not possible. This review summarizes interactions that exist between these organic compounds by themselves in the solid state, as well as those in coordination polymers with metal ions and in polyoxometalate‐based hybrids. Complexes based on pyrazine ligands can generate metal–organic framework (MOF) structures that bind polyoxometalates (POMs) through covalent and noncovalent interactions. Some biological and magnetic properties involving these compounds are considered and the effect of hydrogen bonding on their supramolecular architectures is highlighted.