Cup-shaped E,E-stilbenophane: synthesis,crystal structure and supramolecular chemistry

A new E,E-stilbenophane was synthesised and characterised. The crystal structure of this cyclophane shows that this molecule has a cup-shaped structure, which hosts a phenyl ring of neighbouring molecule as guest in its cavity with a π–π distance of about 3.7 Å. Moreover, the NMR spectra and theoretical analysis (gauge-independent atomic orbitals (GIAO) and quantum theory of atoms in molecules (QTAIM)) suggest that the silver recognition by E,E-stilbenophane host molecules is based on cation–π interactions in which the π-electrons of the double bonds play a major role.     

Correlations of ion structure with multiple fragmentation pathways arising from collision‐induced dissociations of selected α‐hydroxycarboxylic acid anions

Under conditions of collision‐induced dissociation (CID), anions of α‐hydroxycarboxylic acids usually fragment to yield the distinctive hydroxycarbonyl anion (m/z 45) and/or the complementary product anion formed by neutral loss of formic acid (46 u). Further support for the known two‐step mechanism, involving an ion‐neutral complex for the formation of the hydroxycarbonyl anion from the carboxyl group, is herein provided by tandem mass spectrometric results and density functional theory computations on the glycolate, lactate and 3‐phenyllactate ions. A fourth, structurally related α‐hydroxycarboxylate ion, obtained by deprotonation of mandelic acid, showed only loss of carbon dioxide upon CID. Density functional theory computations on the mandelate ion indicated that similar energy inputs were required for a direct, phenyl‐assisted decarboxylation and a postulated novel rearrangement to a carbonate ester, which yielded the benzyl oxide ion upon loss of CO₂. Rearrangement of the glycolate ion led to expulsion of carbon monoxide, whereas the 3‐phenyllactate ion showed the loss of water and formation of the benzyl anion and the benzyl radical as competing processes. The fragmentation pathways proposed for lactate and 3‐phenyllactate are supported by isotopic labeling. The relative computed energies of saddle points and product ions for all proposed fragmentation pathways are consistent with the energies supplied during CID experiments and the observed relative intensities of product ions. The diverse reaction pathways characterized for this set of four α‐hydroxycarboxylate ions demonstrate that it is crucial to understand the effects of structural variations when attempting to predict the gas‐phase reactivity and CID spectra of carboxylate ions. Copyright © 2013 John Wiley & Sons, Ltd.     

《新编高聚物的结构与性能》编写心得——(1)教材乃教学之本

教材乃教学之本,一本好的教材会影响好几代学生。本文以《新编高聚物的结构与性能》的编写为例,提出教材编写要建立在深入、持久的教学研究基础上,写专业课教材一定要有自己的科研工作,教材撰写者应尽量反映本国学者科研成果,编写教材要有不怕慢、只怕停的坚韧性等四个原则。此外,还探讨了教材编写中存在的问题。     

Site-specific C content by quantitative isotopic C Nuclear Magnetic Resonance spectrometry: A pilot inter-laboratory study

Isotopic ¹³C NMR spectrometry, which is able to measure intra-molecular ¹³C composition, is of emerging demand because of the new information provided by the ¹³C site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic ¹³C NMR as a routine tool. This paper describes the first collaborative study of intra-molecular ¹³C composition by NMR. The main goals of the ring test were to establish intra- and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic ¹³C NMR was then assessed on vanillin from three different origins associated with specific δ¹³C_i profiles. The standard deviation was, on average, between 0.9 and 1.2‰ for intra-variability. The highest standard deviation for inter-variability was 2.1‰. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of δ¹³C_i in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results.     

Skin Constituents as Cosmetic Ingredients. Part II: A Study of Bio‐Mimetic Monoglycerides Behavior at the Squalene‐Water Interface by the “Pendant Drop” Method in a Dynamic Mode

This work aims at presenting the viscoelastic behavior of bio‐mimetic monoglycerides used as emulsifier in a mixture made of two non‐miscible liquids, squalene and water. The measurement of the interfacial tension, carried out by the “pendant drop” method in “dynamic” mode, made it possible to characterize these amphiphilic molecules according to the value of their elastic modulus, ?, as well as their relaxation time, τ_R.

The analysis of these parameters, as well as those developed in the previous publication [L. Blasco et al. (2006) Skin constituents as cosmetic ingredients. Part I: A Study of bio‐mimetic monoglyceride behavior at the squalene‐water interface by the “pendant drop” method in a static mode. J. Dispers. Sci. Technol., 27(6).] shows that the hydrocarbon chain structure, such as its length, the presence of one or more unsaturations, hydroxyl function, affects the behavior of surfactant molecules at the squalene/water interface.     

Quantitation of perfluoroalkyl acids,parabens and cotinine from single low volume serum sample by validated analytical method

ABSTRACT

In this paper, we present the results of an analytical method that has been recently developed, validated and successfully applied in a biomonitoring approach. In the environmental pollutant studies it is desirable that the analytical method can determine multiple classes of compounds from a single, small volume sample. The presented analytical method with a simple sample pre-treatment allows the quantitation of 13 perfluoroalkyl acids (PFAAs), 6 parabens and cotinine (used as nicotine biomarker) from a single, small volume of 100 µL serum sample by liquid chromatography-triple quadrupole mass spectrometer (LC-MS/MS). The limits of quantitation (LOQ) for PFAAs, parabens and cotinine were 0.10–0.50, 0.20–0.80 and 0.10 ng/mL, respectively. Besides sensitivity the method has excellent trueness/accuracy and repeatability. The trueness of the method for the determination of PFAAs ranged from 95% to 106% and the repeatability (as RSD %) from 0.6% to 5.6%. The accuracy and RSD for parabens were 73–120% and 1.3–9.7%, respectively, and 100–106% and 1.3–3.5 % for cotinine. Biomonitoring data reveals the presence of several PFAAs and parabens in serum samples of Finnish population. The total concentrations for PFAAs and parabens were from 2.0 to 33 ng/mL and from <LOQ to 1100 ng/mL, respectively. Nearly all non-smokers had the serum cotinine concentration below 1.0 ng/mL, which can be suggested as the cut point for cotinine concentration to identify smoking.     

Synthesis and mesomorphic investigation of calamitic liquid crystalline system ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB): A temperature dependent micro-Raman study and DFT calculations

A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of CH in-plane bending and CO stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the CH in-plane bending to shift lower and CO stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal → smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.     

Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7·H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates

Calcium pyrophosphate hydrate (CPP, Ca₂P₂O₇·nH₂O) and calcium orthophosphate compounds (including apatite, octacalcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetrahydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological interest. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca₂P₂O₇·H₂O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X‐ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetrahydrated calcium pyrophosphate β phase (CPPT‐β) is discussed.     

面向高阶思维培养的自主型实验教学模式的设计与实践*

基于教育现代化、发展“互联网+教育”、培养创新性人才的指导思想,结合“超星学习通”网络平台与实验课堂的优势,设计了面向高阶思维培养的“预习自测-讲授讨论-自主实践-总结反思”的四段自主型实验教学模式,并应用于化学与化工类专业分析化学实验课程的教学实践。该实验教学模式增加了学生自主学习时间,培养了学生“分析、综合、评价和创造”等高阶思维能力,提高了实验课程的教学效率,为高等院校实践实验教学的改革提供了参考依据。     

PBL教学模式在中美高校化学实验课教学中应用的对比研究

因课程设置、学情等不同, PBL教学模式在中美高校化学实验课的实施过程中各具特色。本文从教材、课程考核、师资培训、研究机构和基金等4个角度客观分析PBL教学模式在中美2国高校化学实验课应用中的差异,并在此基础之上提出,应该客观公正地看待这种差异,树立文化自信。