Addition of some α-halo ethers to unsaturated compounds

Summary The addition was carried out of 2-acetoxyethyl chloromethyl ether and of 2-chloroethyl chloromethyl ether to isobutene, to allyl chloride, to styrene, and to allyl acetate and also of 2-acetoxyethyl chloromethyl ether to butadiene and to ethyl cinnamate.     

How mobile NMR can help with the conservation of paintings

The conservation of paintings is fundamental to ensure that future generations will have access to the ideas of the grand masters who created these art pieces. Many factors, such as humidity, temperature, light, and pollutants, pose a risk to the conservation of paintings. To help with painting conservation, it is essential to be able to noninvasively study how these factors affect paintings and to develop methods to investigate their effects on painting degradation. Hence, the use of mobile nuclear magnetic resonance (NMR) as a method of investigation of paintings is gaining increased attention in the world of Heritage Science. In this mini-review, we discuss how this method was used to better understand the stratigraphy of paintings and the effect different factors have on the painting integrity, to analyze the different cleaning techniques suitable for painting conservation, and to show how mobile NMR can be used to identify forgeries. It is also important to keep in mind its limitations and build upon this information to optimize it to extend its applicability to the study of paintings and other precious objects of cultural heritage.     

A second-order perturbation theory route to vibrational averages and transition properties of molecules: general formulation and application to infrared and vibrational circular dichroism spectroscopies

A general formulation to compute anharmonic vibrational averages and transition properties at the second-order of perturbation theory is derived from the Rayleigh-Schro?dinger development. This approach is intended to be applicable to any property expanded as a Taylor series up to the third order with respect to normal coordinates or their associated momenta. The equations are straightforward to implement and can be easily adapted to various properties, as illustrated for the case of electric and magnetic dipole moments. From those, infrared and vibrational circular dichroism spectra can be readily obtained. This fully automatic procedure has been applied to several chiral molecules of small-to-medium sizes and compared to the standard double harmonic approximation and to experimental data.     

Size-Exclusion Chromatography: A Twenty-First Century Perspective

Now in its sixth decade, size-exclusion chromatography (SEC) remains the premier method by which to determine the molar mass averages and distributions of natural and synthetic macromolecules. Aided by its coupling to a variety and multiplicity of detectors, it has also shown its ability to characterize a host of other physicochemical properties, such as branching, chemical, and sequence length heterogeneity size distribution; chain rigidity; fractal dimension and its change as a function of molar mass; etc. SEC is also an integral part of most macromolecular two-dimensional separations, providing a second-dimension size-based technique for determining the molar mass of the components separated in the first dimension according to chemical composition, thus yielding the combined chemical composition and molar mass distributions of a sample. While the potential of SEC remains strong, our awareness of the pitfalls and challenges inherent to it and to its practice must also be ever-present. This Perspective aims to highlight some of the advantages and applications of SEC, to bring to the fore these caveats with regard to its practice, and to provide an outlook as to potential areas for expansion and growth.

     

杨石先对农药化学学科的重要贡献及其学术思想

杨石先先生一生献身于我国的教育事业与化学学科的发展,在62年中为我国培养了无数高质量的科教人才。他除了长期担任南开大学校长之外, 还创建了我国大学第一个专职研究所,即元素有机化学研究所。他率先开展了我国元素有机化学与农药化学的科学研究,领导了元素有机化学国家重点实验室的建立,是我国元素有机化学和农药化学的奠基人和开拓者。他倡导用有机化学的专业知识,科学和系统地开展农药化学研究,组建队伍获得20项科研成果,发表上百篇科学与论述性论文,为我国开展自主创新农药研究事业作出重要贡献。在农药化学学科的学术思想中,他强调要弄清该学科的交叉性、系统性和内在规律性,倡导要学习国际先进经验,要结合国情自主创新,要为国家经济服务,要对世界农药科技做出贡献。他毕生对人才培养给予了特别的重视,为我国科技事业持续发展作出了重大贡献。     

半夏淀粉的理化特性

研究了不同产地的4种半夏淀粉的理化特性,包括直链淀粉含量、膨胀度、溶解性、持水性、淀粉粒大小和形貌、结晶类型、热特性和糊化特性等。结果表明,这些半夏淀粉中直链淀粉含量为18.60%～23.91%;膨胀度21.53%～23.09%;溶解度11.5%～32.3%;持水性100.3%～119.0%。淀粉粒单粒球形,卵形或圆半球形,直径2～20μm,复粒由2～3个分粒组成,其结晶类型均为C型,结晶度15.0%～37.9%。用差示扫描量热仪测得的转变温度TO、TP和TC分别为71.58～77.75℃、83.03～83.84℃和89.41～90.99℃,热焓为4.316～5.809 J/g。用快速粘度分析仪测定了4种半夏淀粉的糊化特征值:峰值粘度、热糊粘度、冷糊粘度、稀懈值和回复值分别为149.5～226.2、97.7～127.2、141.8～194.3、50.4～99.0和44.2～67.2 RVU。糊化温度77.8～79.9℃,峰值时间8.3～8.7 min。     

Manganese Kβ X-ray emission spectroscopy as a probe of metal-ligand interactions

A systematic series of high-spin mononuclear Mn(II), Mn(III), and Mn(IV) complexes has been investigated by manganese Kβ X-ray emission spectroscopy (XES). The factors contributing to the Kβ main line and the valence to core region are discussed. The Kβ main lines are dominated by 3p-3d exchange correlation (spin state) effects, shifting to lower energy upon oxidation of Mn(II) to Mn(III) due to the decrease in spin state from S = 5/2 to S = 2, whereas the valence to core region shows greater sensitivity to the chemical environment surrounding the Mn center. A density functional theory (DFT) approach has been used to calculate the valence to core spectra and assess the contributions to the energies and intensities. The valence spectra are dominated by manganese np to 1s electric dipole-allowed transitions and are particularly sensitive to spin state and ligand identity (reflected primarily in the transition energies) as well as oxidation state and metal-ligand bond lengths (reflected primarily in the transition intensities). The ability to use these methods to distinguish different ligand contributions within a heteroleptic coordination sphere is highlighted. The similarities and differences between the current Mn XES study and previous studies of Fe XES investigations are discussed. These findings serve as an important calibration for future applications to manganese active sites in biological and chemical catalysis.     

和医学相关有机化合物绿色鉴别实验的设计*

为了将医用化学实验中“有机化合物的鉴别”实验更加密切地与医学相关专业结合,并提高实验操作的安全性,降低化学试剂的毒性与刺激性,甄选出一系列与医学密切相关的有机化合物作为待鉴别试剂,同时设计绿色环保、安全低毒、现象明显、操作简便、成本低廉的鉴别方法,为学生实验方案的设计提供指导。以期提高医学生学习的积极性与主动性,促进学生灵活运用知识分析问题、解决问题,为相关教学工作的改进提供借鉴意义。     

Designing for sustainability with biocatalytic and chemoenzymatic cascade processes

Cascade reactions have been widely recognized to cut costs, decrease solvent usage, and reduce cycle times in chemical processes. Recently, biocatalytic cascades have altered how we design synthetic routes to complex molecules to achieve sustainable commercial processes for pharmaceutical, agricultural, and fine chemical industries. With advancements in protein engineering and an increase in the number of enzyme classes available to chemists, industrial and academic groups alike have endeavored to expand the scope of biocatalysis from single reactions to multi-enzyme cascades to rapidly build complex molecular structures. Recent reports have drawn inspiration from biosynthetic pathways and have applied engineered enzymes to in vitro enzymatic cascades. Furthermore, combining transition-metal catalysis and enzymes in one-pot chemoenzymatic cascades likewise serves to broaden the scope of biocatalysis, enabling traditional chemical reactions to be performed under mild aqueous conditions. In this article, we review recent biocatalytic and chemoenzymatic cascades from 2019 to 2021.     

“The Fitness of Their Union”: Travel and Health in the Letters of Humphry and Jane Davy

The letters of Humphry Davy and his circle, to be published shortly, shed new light on his marriage to Jane Apreece. This paper examines the journeys undertaken by the couple, together and separately, with particular attention to the therapeutic benefits they sought from travel. I argue that their increasingly divergent itineraries reflected a growing understanding that Humphry and Jane had different humoral temperaments or constitutions, leading them to seek different climatic conditions to cure their ailments. While Jane’s temperament was classified as melancholic, requiring her to travel to warmer and sunnier climes during the English winter, Humphry’s was believed to be sanguine, meaning he had to avoid excessive heat along with stimulating food and drink. He relied on classical ideas about individuals’ different humoral constitutions, and the therapies appropriate to them, while measuring atmospheric variables to determine the best places to restore his health. The Davys’ letters reveal the beliefs about bodily differences and atmospheric conditions that shaped their therapeutic travels.     

Precision of Flash Pyrolysis-GC-MS Analysis: Experimental Evaluation of the Sources of Variability

The present study was carried out to evaluate the precision and to identify significant sources of variability in flash pyrolysis-GC-MS experiments. The analysis of variance has been applied to the example of polyethylene pyrolysis to estimate the impact of several controlled factors: sample handling, flash pyrolysis filament ageing and calibration. It was demonstrated that to get the best precision in experimental results, it is recommended to set the operator to reduce the impact of sample handling procedure and the filament to avoid variability due to changes in filament characteristics. In comparison, filament ageing and filament calibration are shown to influence in a limited extent the experimental results.     

Functional molecules in electronic circuits

Molecular electronics is a fascinating field of research contributing to both fundamental science and future technological achievements. A promising starting point for molecular devices is to mimic existing electronic functions to investigate the potential of molecules to enrich and complement existing electronic strategies. Molecules designed and synthesized to be integrated into electronic circuits and to perform an electronic function are presented in this article. The focus is set in particular on rectification and switching based on molecular devices, since the control over these two parameters enables the assembly of memory units, likely the most interesting and economic application of molecular based electronics. Both historical and contemporary solutions to molecular rectification are discussed, although not exhaustively. Several examples of integrated molecular switches that respond to light are presented. Molecular switches responding to an electrochemical signal are also discussed. Finally, supramolecular and molecular systems with intuitive application potential as memory units due to their hysteretic switching are highlighted. Although a particularly attractive feature of molecular electronics is its close cooperation with neighbouring disciplines, this article is written from the point of view of a chemist. Although the focus here is largely on molecular considerations, innovative contributions from physics, electro engineering, nanotechnology and other scientific disciplines are equally important. However, the ability of the chemist to correlate function with structure, to design and to provide tailor-made functional molecules is central to molecular electronics.     

Gas chromatographic determination of some glycol ethers and glycol ether acetates by FID,O-FID,and MS detection. Preliminary applications in simultaneous monitoring of these chemicals in biological matrices

Twelve compounds, commonly used as industrial solvents and belonging to the chemical class of glycol ethers and glycol ether acetates, were investigated. Several analytical conditions, applied to single or connected capillary columns of different length and polarity coating and connected to FID, O-FID and MS detection systems, were assayed. Tests on heptafluorobutyryl derivatives were also attempted to improve the analytical sensitivity. The aims were to establish gas chromatographic methods suitable for analysis of reference standard compounds and to verify their applicability to biological matrix analysis for pharmacokinetic and toxicological studies, since these chemicals have been shown to be hazardous in laboratory animals and are presumed to be dangerous in man.     

Advanced Reprocessing Developments in Europe Status on European Projects ACSEPT and ACTINET-I3

Nuclear energy has more than ever to demonstrate that it can contribute safely and on a sustainable way to answer the international increase in energy needs. Actually, in addition to an increased safety of the reactors themselves, its acceptance is still closely associated to our capability to reduce the lifetime of the nuclear waste, to manage them safely and to propose options for a better use of the natural resources. Spent fuel reprocessing can help to reach these objectives. At the European level, ACSEPT and ACTINET-I3 have worked together to improve our knowledge in actinide chemistry and advanced separation process development.     

成都经济生态区大气降尘中镉赋存形态的研究

采用Tessier连续提取法对成都经济生态区不同区域的24个大气降尘样中镉的赋存形态进行了研究。研究结果表明,大气降尘中的镉主要以残留态形态存在;各形态镉在总镉中所占百分比含量由大到小排列顺序依次是:残留态,碳酸盐结合态,交换态,铁锰结合态,有机结合态;交换态镉、碳酸盐结合态镉这两种具有较高生物有效性的形态镉在总镉中所占的平均百分比含量分别是6.420%和8.917%;铁锰氧化物结合态、有机结合态、残留态镉这三种形态镉生物有效性很低,分别在总镉中所占的平均百分比含量分别是3.419%、2.365%和78.907%。通过分析可得出,汽油和煤的燃烧以及工厂排放镉能加大城市大气降尘的镉污染。     

中职本科贯通应用型人才培养的无机化学教学探索

中职本科贯通生的中职阶段学习与普通高中学习存在着较大的区别,由于对基础知识未进行过系统强化训练,中职学生的理论知识较为薄弱;但由于较早进相关工厂见习或顶岗操作,其形象思维能力较强。在无机化学教学中,根据中职本科贯通生的特点,多采取探究式教学,让学生根据工厂生产中遇到的情况用自己的语言来描述一些概念和定义,"发现"一些原理,有利于培养应用型人才。     

Free-energy component analysis of 40 protein-DNA complexes: a consensus view on the thermodynamics of binding at the molecular level

Noncovalent association of proteins to specific target sites on DNA--a process central to gene expression and regulation--has thus far proven to be idiosyncratic and elusive to generalizations on the nature of the driving forces. The spate of structural information on protein--DNA complexes sets the stage for theoretical investigations on the molecular thermodynamics of binding aimed at identifying forces responsible for specific macromolecular recognition. Computation of absolute binding free energies for systems of this complexity transiting from structural information is a stupendous task. Adopting some recent progresses in treating atomic level interactions in proteins and nucleic acids including solvent and salt effects, we have put together an energy component methodology cast in a phenomenological mode and amenable to systematic improvements and developed a computational first atlas of the free energy contributors to binding in approximately 40 protein-DNA complexes representing a variety of structural motifs and functions. Illustrating vividly the compensatory nature of the free energy components contributing to the energetics of recognition for attaining optimal binding, our results highlight unambiguously the roles played by packing, electrostatics including hydrogen bonds, ion and water release (cavitation) in protein-DNA binding. Cavitation and van der Waals contributions without exception favor complexation. The electrostatics is marginally unfavorable in a consensus view. Basic residues on the protein contribute favorably to binding despite the desolvation expense. The electrostatics arising from the acidic and neutral residues proves unfavorable to binding. An enveloping mode of binding to short stretches of DNA makes for a strong unfavorable net electrostatics but a highly favorable van der Waals and cavitation contribution. Thus, noncovalent protein-DNA association is a system-specific fine balancing act of these diverse competing forces. With the advances in computational methods as applied to macromolecular recognition, the challenge now seems to be to correlate the differential (initial vs. final) energetics to substituent effects in drug design and to move from affinity to specificity.     

Determination of gaseous and particulate carbonyls in air by gradient-elution micellar electrokinetic capillary chromatography

A new continuous-flow gradient-elution micellar electrokinetic capillary chromatography method is developed for the determination of airborne carbonyls after derivatization with 2,4-dinitrophenylhydrazine. A total of 16 carbonyls can be determined with detection limits ranging from 0.94 to 8.50 mg/L, working range from 4.72 to 346 mg/L, and repeatabilities (relative standard deviation, n=5) from 1.23 to 4.6% or 3.93 to 7.6% for migration time and peak area, respectively. Coupling with denuder-filter sampling, a preliminary survey has been conducted to determine gaseous and particulate carbonyls from air sampled at a roadside station. The method is shown to have sufficient sensitivity for 1-h sampling of ambient carbonyls with detection limits ranging from 0.045 to 1.2 microg/m3 and working range from 0.11 to 43.3 microg/m3 at a flow rate of 10 Lpm. The method requires minimal modification of commercially available capillary electrophoresis equipment and can differentiate gaseous and particulate carbonyls to provide essential information and objective data for adopting effective measures to combat the discharge of carbonyl compounds to the atmosphere.     

Hygienic aspects related to burial

Burial grounds are generally provided by local authorities in cemeteries (subject to planning consent and to compliance with any considerations for environmental health). Their design has been submitted to studies of hydrogeological characteristics of soil with regard to its ability to purify wastewater coming from corpse decomposition, its ability to avoid the infiltration of pollutants in groundwater, and its ability to skeletonize buried corpses within the given times foreseen by the law in force. Greater environmental awareness has necessitated that new and existing burial grounds are assessed to determine the environmental load which they could release to soil or any downstream component. This problem arises in countries where there is a high density of built-up areas, a custom of disposing of the dead by burial, a lack of available spaces and suitable soils to designate as burial grounds. This paper reports some results from a study carried out on ground lands of Italy in order to revise articles 82 and 83 of the Decree No 285 of 1990 in force in relation to burial grounds. Soil permeability to water and air is a parameter of critical importance in relation to purification and/or diffusion of leachates from inhumed corpses in the soil, and in relation to its influence on the time necessary to completely skeletonize a human corpse.