Thermokinetics of the Formation Reaction of Zinc Histidine Complex

The enthalph change of reaction of zinc chloride with L-α-histidine in the temperature range of 25-50℃ has been determined by a microcalorimeter.On the basis of experimental and calculated results,three thermodynamics parameters (the activation enthalpy,the activation entropy,the activation free energy),the rate constant and three kinetic parameters (the activation energy,the pre-exponential constant and the reaction order) of the reaction,and the standard enthalpy of formation of Zn(His)^2 (aq.) are obtained.The results showed that the title reaction easily took place at the studied temperature.     

Improving the Halogen–Magnesium Exchange by using New Turbo-Grignard Reagents

This Minireview describes the scope of the halogen–magnesium exchange. It shows that the use of the turbo-Grignard reagent (iPrMgCl⋅LiCl) greatly enhances the rate of the Br– and I–Mg exchange. Furthermore, this magnesium reagent allows the performance of a fast sulfoxide–magnesium exchange. Also, the use of sBuMgOR⋅LiOR (R=2-ethylhexyl) enables a Br–Mg exchange in toluene leading to various Grignard reagents in toluene. Additionally, the new exchange reagent sBu₂Mg⋅2 LiOR (R=2-ethylhexyl) further increases the rate of the halogen–magnesium exchange allowing one to perform a chlorine–magnesium exchange for aromatic chlorides bearing an ortho-methoxy substituent in toluene.     

Recent Advances in One-Electron-Oxidized CuII–Diphenoxide Complexes as Models of Galactose Oxidase: Importance of the Structural Flexibility in the Active Site

The phenoxyl radical plays important roles in biological systems as cofactors in some metalloenzymes, such as galactose oxidase (GO) catalyzing oxidation of primary alcohols to give the corresponding aldehydes. Many metal(II)–phenoxyl radical complexes have hitherto been studied for understanding the detailed properties and reactivities of GO, and thus the nature of GO has gradually become clearer. However, the effects of the subtle geometric and electronic structural changes at the active site of GO, especially the structural change in the catalytic cycle and the effect of the second coordination sphere, have not been fully discussed yet. In this Review, we focus on further details of the model studies of GO and discuss the importance of the structural change at the active site of GO.     

Theoretical Study of the Isomerization Reaction of 1-3 H Transfer on Formamidine Substituted by Halogen

The ab initio method has been used to study the 1-3 H transfer reaction on formamidine substituted by halogen. The calculation results show that the substituted halogen has two effects on the 1-3 H transfer reaction: decreasing the activation energy and stabilizing the C=N double bond owing to the conjugative effect of p-π-p of products and transition states.     

Studies on Ester Exchange Reaction

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Recent Developments in Kramers’ Theory of Reaction Rates

In this short review, we provide an update of recent developments in Kramers’ theory of reaction rates. After a brief introduction stressing the importance of this theory initially developed for chemical reactions, we briefly present the main theoretical formalism starting from the generalized Langevin equation and continue by showing the main points of the modern Pollak, Grabert and Hänggi theory. Kramers’ theory is then sketched for quantum and classical surface diffusion. As an illustration the surface diffusion of Na atoms on a Cu(110) surface is discussed showing escape rates, jump distributions and diffusion coefficients as a function of reduced friction. Finally, some very recent applications of turnover theory to different fields such as nanoparticle levitation, microcavity polariton dynamics and simulation of reaction in liquids are presented. We end with several open problems and future challenges faced up by Kramers turnover theory.     

Electrodeposition of Zinc–Nickel–CNT Composite Coatings in the Pulsed Mode

Composite electrochemical coatings based on the zinc–nickel alloy and modified with carbon nanotubes were produced in the pulsed mode. The functional properties (friction coefficient, protective capacity) of the composite coatings were examined in comparison with zinc–nickel alloys without a dispersed phase. It was found that, as carbon nanotube particles are incorporated into zinc–nickel deposits, the sliding-friction coefficient decreases by a factor of 1.30–1.40, and the range of passive-state potentials becomes 1.55–1.65 times wider.     

Synthesis of 1,2-Diazepines by the Bischler–Napieralski Reaction

A new strategy has been proposed for the synthesis of 5H-[1]benzofuro[2,3-d][1,2]diazepines containing two aryl substituents in the diazepine fragment. The key stage of the synthesis is intramolecular cyclization of the corresponding hydrazides under the Bischler–Napieralski reaction conditions.     

Some Recent Advances in the Design and Use of Molecular Balances for the Experimental Quantification of Intramolecular Noncovalent Interactions of π Systems

Herein, various molecular balances used for comparing the strengths of intramolecular noncovalent interactions are reviewed. Our overview indicates that considerable quantitative insight into the strength of noncovalent interactions can be gained through the careful design of molecular balances. Many exciting opportunities certainly exist for the design of further new balances to quantify and dissect the relative strengths of noncovalent interactions as a function of solvation and the importance of the many factors that contribute to overall molecular recognition. However, even simple model molecules can show a multiplicity of intramolecular noncovalent interactions acting in a combined fashion. It is therefore essential to undertake a detailed computational analysis to identify all possible noncovalent interactions present in a selected molecular balance prior to a quantitative experimental assessment of the strength of a particular noncovalent interaction. It is also argued that the words “torsion” and “molecular balance” seem to have become inextricably linked and, in consequence, even top pan and seesaw balances have been mistakenly referred to in these terms.     

Recent Advances and Perspectives in Transition Metal-Catalyzed 1,4-Functionalizations of Unactivated 1,3-Enynes for the Synthesis of Allenes

Classic methods for the synthesis of allenes usually introduce only one functional group into products.In this review,we highlight the recent advances and perspectives in the synthesis of allenes by transition metal-catalyzed 1,4-functionalization of unactivated 1,3-enynes.     

Recent progress in the design of G-quadruplex–based electrochemical aptasensors

Aptamer-based electrochemical sensors are now developed for the detection of a wide variety of analytes including ions, low-molecular-weight molecules, proteins, and living cells. An aptamer-based sensor is an analytical device whose bio-sensing element (i.e. the aptamer) is immobilized on a transducer surface. Aptasensors have attracted great attention because of their high selectivity, sensitivity, and stability; they could be miniaturized and are of low production cost and offer extraordinary flexibility in the design of their assemblies. This review will emphasize recent developments of aptasensors using aptamers that are able to adopt the particular G-quadruplex (G4) conformations, which are secondary DNA structures formed from guanine-rich sequences. Indeed, G4 exhibits notable recognition properties inherent to their particular structuration.     

Recent advances on the structure–properties relationship of multiblock copolymers

Multiblock copolymers represent a fascinating class of materials that sits at the very heart of industrial applications and fundamental polymer science. They are most often made of a linear succession of incompatible “soft” and “hard” segments that microphase separate at room temperature while they can be easily re-homogenized upon heating. This thermoreversible character provides them with decisive advantages with respect to other rubber-based materials such as vulcanized elastomers, making them indispensable for the development of a more sustainable polymer industry. Beyond practical opportunities, tailoring the multiblock copolymers morphology has a pivotal role to play in the fundamental understanding of the structure–properties relationship of polymer-based systems. It notably serves to comprehend complex materials such as semicrystalline homopolymers and nanocomposites. Aside from the thorough work developed on well-defined diblock copolymers for half a century, this article review aims to guide the reader into the more intricate world of multiblock copolymers by providing him/her quantitative tools to connect chemical nature, microstructure and mechanical properties.     

Anomalies in the Change of Volumetric Parameters of the Diels–Alder Reaction in Solution

In this article negative values of the activation volume in retro-Diels–Alder reactions are interpreted in terms of the different possibilities of penetration of the solvent molecules into the sterically branched structures of the adduct and activated complex. Empty spaces, inaccessible to penetration of solvent molecules, lead to increases of the molar volume of the screened adducts in solution and, consequently, to a less negative value of the Diels–Alder reaction volume. The values of partial molar volumes of anthracene, maleic anhydride and the adducts cyclopentadiene–maleic anhydride, anthracene–maleic anhydride and anthracene–tetracyanoethylene, in several solvents, were calculated from the solution density data.     

Recent topics of the natural product synthesis by Horner–Wadsworth–Emmons reaction

The Horner–Wadsworth–Emmons (HWE) reaction has become well established among existing methodologies for the highly stereoselective olefination of carbonyl compounds. The reliability of this reaction in terms of its robustness, high stereoselectivity, and broad substrate scope permit retrosynthetic disconnection of the olefin bond in α,β-unsaturated carbonyl intermediates in natural product synthesis. This review discusses recent applications of the HWE reaction in natural product synthesis, highlighting its use for carbon chain elongation, coupling reactions of synthetic segments, ring-closing reactions, tandem reactions including HWE olefination, and asymmetric reactions.     

Direct Correlation Between the H/D Exchange Reaction and Conformational Changes of the Cation in Imidazolium-Based Ionic Liquid–D2O Mixtures

We present a study on the effects of deuterated water on the conformational equilibria of the imidazolium cation in aqueous mixtures of imidazolium-based ionic liquids at room temperature. We provide spectroscopic evidence that the conformational dynamics of the imidazolium cation in D₂O are directly related to the H/D exchange reaction of the C–H group at position 2 on the imidazolium ring. The relation is supported by comparing Raman spectra obtained from solutions prepared with H₂O and D₂O.     

Synthesis of Macrocyclic Depsipeptides via the Passerini–Click Reaction Strategy

Russian Journal of Organic Chemistry - A combination of the Passerini reaction and copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC, click reaction) was used to synthesize...     

Recent strategic advances for the activation of benzylic C–H bonds for the formation of C–C bonds

Alkylarenes, obtained from abundant hydrocarbon feedstock sources, are an attractive starting material for the formation of complex molecular architectures. Conventional activation strategies of the relatively inert sp³-hybridized benzylic C–H bonds usually require relatively harsh conditions and are difficult to apply to the synthesis of fine chemicals. The present review describes recent strategic advances for the activation of benzylic C–H bonds for the catalytic formation of C–C bonds. In particular, two activation methods, i.e., strategies that generate benzylic radicals or benzyl anions, are discussed.     

Recent Trends in the Chemistry of Heterocyclic Sulfides, 1990–2000

This review selectively describes work that generally reflects the recent current state of knowledge about heterocyclic sulfides while emphasizing important developments, methods of synthesis, main reactions, and their biological activities.     

Fine-Tuning Substrate–Catalyst Halogen–Halogen Interactions for Boosting Enantioselectivity in Halogen-Bonding Catalysis

A new approach towards highly enantioselective halogen-bonding catalysis has been developed. To circumvent the intrinsic issues of the nature of the halogen-bond (XB) and the resultant unresolved limitations in asymmetric catalysis, fine-tuned halogen–halogen interactions between the substrate and XB-donor were designed to preorganize the substrate in the catalyst's cavity and boost enantiocontrol. The present strategy exploits both the electron cloud (Lewis base site) and the sigma (σ)-hole site of the halogen substituent of the substrates to form a tight catalyst–substrate–counteranion chiral complex, thus enabling a controlled induction of high levels of chirality transfer. Remarkable enantioselectivities of up to 95 : 5 e.r. (90 % ee) have been achieved in a model dearomatization reaction of halogen-substituted (iso)quinolines with tetrakis-iodotriazole multidentate anion-binding catalysts.     

Recent Advances in Metal–Organic Frameworks for Photo-/Electrocatalytic CO2 Reduction

Considerable attention has been paid to the utilization of CO₂, an abundant carbon source in nature. In this regard, porous catalysts have been eagerly explored with excellent performance for photo-/electrocatalytic reduction of CO₂ to high valued products. Metal–organic frameworks (MOFs), featuring large surface area, high porosity, tunable composition and unique structural characteristics, have been widely exploited in catalytic CO₂ reduction. This Minireview first reports the current progress of MOFs in CO₂ reduction. Then, a specific interest is focused on MOFs in photo-/electrocatalytic reduction of CO₂ by modifying their metal centers, organic linkers, and pores. Finally, the future directions of study are also highlighted to satisfy the requirement of practical applications.