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Density functional theory (DFT) was used to study the mechanism of Diels–Alder (DA) reaction between 2‐Methyl‐ 1,3 Butadiene (MBD) with B12N12, B6N6C12 and B6C12N6 fullerens in the gas phase. In this mechanism, B‐N bonds of four‐membered and six‐membered rings of nanocages were chosen to react with MBD. Due to the existence of two types of B‐N bonds, two competitive pathways (a and b) were investigated. The effect of the substitution of carbon atoms instead of boron and nitrogen atoms on the stability of the structures and the regioselectivity of the DA reaction was examined. The potential energy of all structures and the activation barrier for all reaction pathways was evaluated. The chemical reactivity of fullerens using the molecular quantum descriptors was assessed. To evaluate the global electron density transfer in transition states (TS) structures, the natural bond orbital (NBO) analysis was performed. [ABSTRACT FROM AUTHOR]

Silymarin has been utilized as a traditional, complementary, and integrative medicine for centuries, despite a poor molecular‐level understanding of its interactions with other medicinal compounds and enzyme structures. However, recent studies indicate that this supplement, as with many others, should be considered with caution because it has the potential to interact with many drugs, medical plants, and foods. Silymarin is composed of several compounds that are either enantiomeric or have similar structures. Thus, this study presents the electronic structure properties and reactivity characteristics of silymarin components and warfarin through density functional theory modeling at the M06‐2X/6–311 + G(d,p) level of theory. The ligand‐protein interactions of the compounds with human serum albumin, cytochrome P450 (CYP2C9, CYP2C19, CYP2D6, and CYP3A4) enzymes, and alanine transaminase were presented using molecular docking. The critical residue‐based interactions of silymarin components and warfarin were fingerprinted. Furthermore, their drug‐likeness and toxicity characteristics were compared to those of warfarin and the well‐known flavonoids, taxifolin, and quercetin. The possibility of inhibiting the target enzymes to reduce the effectiveness of warfarin has been highlighted. [ABSTRACT FROM AUTHOR]

Benzophenone and its derivatives are widely used as UV filters and UV‐ink photoinitiators. The photoinitiating properties of benzophenones depend on their degree of conjugation and delocalization within the molecule. By understanding how conjugation, delocalization, and different substituents affect these properties, benzophenone derivatives can be customized for specific applications. Using quantum mechanical calculations based on B3LYP/6‐311++G(d, p) density functional theory (DFT), chemical reactivity, stability, and photoinitiating capabilities of 4‐(4‐methylphenylthio)benzophenone are analyzed. This includes studying its physical and chemical properties in the gas phase, as well as its excited state electronic transitions, vibrational characteristics, and spectroscopic properties both in gas phase and in various solvents. The DFT‐computed infrared spectra match experimental results. The UV/Visible spectra shows absorption towards longer wavelengths due to extended delocalization of π‐electrons. In different solvents with varying polarity, the absorption spectra exhibit high‐intensity peaks, shift in excitation energy and wavelengths based on the polarity of the solvent. This knowledge allows for the development of novel initiators with customized light absorption, excited state lifetimes, and reaction selectivities, which can enhance processes like UV‐curing, photopolymerization, and other light‐driven reactions. [ABSTRACT FROM AUTHOR]

The reactivity of 22 unsaturated molecules undergoing attack by a methyl radical (⋅CH3) have been elucidated using the condensed radical general‐purpose reactivity indicator (condensed radical GPRI) appropriate for relatively nucleophilic or electrophilic molecules. Using the appropriate radical GPRI equation for electrophilic attack or nucleophilic radical attack, seven different population schemes were used to assign the most reactive atoms in each of the 22 molecules. The results show that the condensed radical GPRI is sensitive to the population scheme chosen, but less sensitive than the radical Fukui function. Therefore, the reliability of these methods depends on the population scheme. Our investigation indicates that the condensed radical GPRI is most accurate in predicting the dominant products of the methyl radical addition reactions on a variety of unsaturated molecules when the Hirshfeld, Merz–Singh–Kollman, or Voronoi deformation density population schemes are used. Furthermore, for all populations schemes in the majority of instances where the radical Fukui function failed the radical GPRI was able to identify the most reactive atom under certain reactivity conditions. [ABSTRACT FROM AUTHOR]

It would be very beneficial to have a method for joining of ceramics to titanium reliably. Although several techniques have been developed and tested to prevent extensive interfacial chemical reactions in titanium‐ceramic systems, the main problem of the inherent brittleness of interfaces was still unsolved. To overcome this problem also in dental applications, we decided to make use of an interlayer material that needs to meet the following requirements: First, it has to be biocompatible, second, it should not melt below the bonding temperatures, and third, it should not react too strongly with titanium, so that its plasticity will be maintained. Considering possible material options only the metals: gold, platinum, palladium, and silver, fulfill the first and second requirements. To find out—without an extensive experimental testing program—which of the four metals fulfills the third requirement best, the combined thermodynamic and reaction kinetic modeling was employed to evaluate how many and how thick reaction layers are formed between the interlayer metals and titanium. With the help of theoretical modeling, it was shown that silver fulfills the last requirement best. However, before starting to test experimentally the effect of the silver layer on the mechanical integrity of dental ceramic/Ag/Ti joints it was decided to make use of mechanical analysis of the three‐point bending test, the result of which indicated that the silver layer increases significantly the bond strength of the joints. This result encouraged us to develop a new technique for plating silver on titanium. Subsequently, we executed numerous three‐point bending tests, which demonstrated that silver‐plated titanium‐ceramic joints are much stronger than conventional titanium‐ceramic joints. Hence, it can be concluded that the combined thermodynamic, reaction kinetic, and mechanical modeling method can also be a very valuable tool in medical research and development work. [ABSTRACT FROM AUTHOR]

In this study, we introduce a novel definition for the electrophilic descriptor. Following the proposal of other researchers, the foundation of our approach lies in expanding the change in the energy of an electronic system using a third‐order Taylor series, leading to the integration of hyperhardness into the formulation of the electrophilic descriptor. To validate our results, we conducted a comparative analysis of reactivity sequences among 35 electrophilic systems with known reactivities, as reported in external experimental studies. The electrophilic descriptor demonstrated a remarkable ability to accurately replicate the relative reactivities of the compounds under consideration, surpassing predictions based solely on the electrophilicity index. These findings underscore the significance of incorporating hyperhardness as a crucial reactivity descriptor. Additionally, our study provides interesting insights into the interpretation of this concept. [ABSTRACT FROM AUTHOR]

Compartmentalization and binding‐triggered conformational change regulate many metabolic processes in living matter. Here, we have synergistically combined these two biorelevant processes to tune the Diels‐Alder (DA) reactivity of a synthetic self‐complexing host‐guest molecular switch CBPQT4+‐Fu, consisting of an electron‐rich furan unit covalently attached to the electron‐deficient cyclobis(paraquat‐p‐phenylene) tetrachloride (CBPQT4+, 4Cl−) host. This design allows CBPQT4+‐Fu to efficiently compartmentalize the furan ring inside its host cavity in water, thereby protecting it from the DA reaction with maleimide. Remarkably, the self‐complexed CBPQT4+‐Fu can undergo a conformational change through intramolecular decomplexation upon the addition of a stronger binding molecular naphthalene derivative as a competitive guest, triggering the DA reaction upon addition of a chemical regulator. Remarkably, connecting the guest to a thermoresponsive lower critical solution temperature (LCST) copolymer regulator controls the DA reaction on command upon heating and cooling the reaction media beyond and below the cloud point temperature of the copolymer, representing a rare example of decreased reactivity upon increasing temperature. Altogether, this work opens up new avenues towards combined topological and supramolecular control over reactivity in synthetic constructs, enabling control over reactivity through molecular regulators or even mild temperature variations. [ABSTRACT FROM AUTHOR]

A simple composite scheme developed for the calculation of accurate reaction barriers, and benchmarked against small systems, is applied here to compute barriers in the BH28 data set published in 2019 by Karton. This set comprises more complex transition states, with up to 7 non‐hydrogen and 10 hydrogen atoms, which barriers calculated at the SVECV‐f12 level are compared to the accurate CCSDT(Q)/CBS values obtained by Karton. A mean absolute difference of 2.4 kJ mol−1 and a root mean square difference of 1.9 kJ mol−1 were obtained, underlying the chemical accuracy of the protocol. [ABSTRACT FROM AUTHOR]

Marine organisms have been found to produce compounds that have the potential to serve as templates for novel therapeutics. Among these compounds, peptides are of particular interest due to their intermediate size between amino acids and proteins. Kahalalides are a family of structurally complex cyclic peptides with potent cytotoxic and antitumor activities, making them promising candidates for cancer therapy. In this study, we investigate the chemical reactivity of Kahalalides A–F using Conceptual Density Functional Theory to gain insight into their bioactivity from a molecular perspective. Our investigation includes characterizing and isolating the peptides, determining their local and global properties and predicting the active reaction sites. We also calculate Bioactivity Scores to predict their biological targets. Overall, this study contributes to the discovery of new therapeutic peptides from natural sources by providing insights into their chemical reactivity and potential biological targets. [ABSTRACT FROM AUTHOR]

Molecular quantum mechanical modeling, accelerated by machine learning, has opened the door to high‐throughput screening campaigns of complex properties, such as the activation energies of chemical reactions and absorption/emission spectra of materials and molecules; in silico. Here, we present an overview of the main principles, concepts, and design considerations involved in such hybrid computational quantum chemistry/machine learning screening workflows, with a special emphasis on some recent examples of their successful application. We end with a brief outlook of further advances that will benefit the field. [ABSTRACT FROM AUTHOR]

Thiazolidinedione (TZD) is one of the privileged heterocyclic rings and has shown many biological applications in medicinal chemistry and drug discovery. This review covers the synthetic approaches of TZD and its derivatives, different synthetic techniques for affording the desired regioselectivity and stereoselectivity, and the techniques that would enhance reaction conditions such as microwave, one‐pot, or ultrasound synthesis. It focuses on synthetic challenges of glitazones and the transformation of other heterocycles to TZD. Moreover, the chemical and biological behavior of TZD through the substitution in the N3 position, modification of the C5 position, annealing in complex heterocyclic systems, and hybridization with other pharmacologically attractive moieties are discussed. All reactions mentioned are provided as possible with different reaction conditions, mechanisms, derivatives scope, yield and clarified by applications of such reactions in the construction of potential medicinal agents. The review also answers questions about rapid racemization of glitazones, their toxicity, considering TZD as pan‐assay interference compounds (PAINS) or not, and the influence of saturation of 5‐position of TZD in their biological activities. This review is a comprehensive guide to make informed decisions for construction of TZD derivatives with biological potentials. [ABSTRACT FROM AUTHOR]

The ability to predict chemical reactivity of a molecule is highly desirable in drug discovery, both ex vivo (synthetic route planning, formulation, stability) and in vivo: metabolic reactions determine pharmacodynamics, pharmacokinetics and potential toxic effects, and early assessment of liabilities is vital to reduce attrition rates in later stages of development. Quantum mechanics offer a precise description of the interactions between electrons and orbitals in the breaking and forming of new bonds. Modern algorithms and faster computers have allowed the study of more complex systems in a punctual and accurate fashion, and answers for chemical questions around stability and reactivity can now be provided. Through machine learning, predictive models can be built out of descriptors derived from quantum mechanics and cheminformatics, even in the absence of experimental data to train on. In this article, current progress on computational reactivity prediction is reviewed: applications to problems in drug design, such as modelling of metabolism and covalent inhibition, are highlighted and unmet challenges are posed. [ABSTRACT FROM AUTHOR]

L-ergothioneine is a low-molecular weight natural product, the chemical structure of which comprises oxygen-, nitrogen- and sulfur-containing functional groups. This gives L-ergothioneine specific physicochemical properties and allows a better understanding of its chemical reactivity, which is primarily due to the 2-thio-imidazole group. Here, a review is provided of how different modes of chemical reactivity account for the reported molecular biological activities of L-ergothioneine. By matching the physicochemical properties to the biological properties of L-ergothioneine, a new perspective of the function and the mode of action of this enigmatic molecule emerges. [ABSTRACT FROM AUTHOR]

Within substitution reactions, the Bimolecular Nucleophilic Substitution (SN2) reaction mechanism is one of the most frequently found and studied ones. Among other factors, the easiness of the SN2 pathway is classically considered to be determined by steric hindrance. However, the diffuse nature of the latter inevitably darkens these and other arguments holding the pillars of chemical intuition. In this work, we employ the steric energy (EST) descriptor, formulated within the Interacting Quantum Atoms approach, to offer insights regarding this problem. The steric demands of the substrate, nucleophile and leaving group were studied using the gas‐phase SN2 reaction with different organic skeletons (CH3, CH3CH2, (CH3)2CH, (CH3)3C, (CH3)3CCH2) and halogens (F, Cl, and Br) as test‐bed systems. Our results show that, according to EST, the SH experienced along these simple reactions fits, in the general case, the trends predicted by a meticulous and rigorous application of chemical intuition. However, steric clash alone should not be considered as the only argument used to explain the easiness of the SN2 reaction over different electrophiles. [ABSTRACT FROM AUTHOR]

Phosphorene or 2D black phosphorus (2D bP) has attracted increasing attention within material scientists in the last decade due to its electronic and photophysical properties as a pristine material. Furthermore, the high chemical reactivity of 2D bP enables the engineering of the outermost superficial layers. This tailored functionalization allows to obtain 2D bP‐based systems such as heterostructures with multiple and/or nonstandard functional properties that can be straightforwardly exploited for real‐setting applications. The aim of this review is to summarize the state of the art on the different strategies in the functionalization of 2D bP such as chemical reactivity with organic molecules, decoration with metal and metal‐oxide nanoparticles, passivation with thin layers of metal oxides or polymers, van der Waals coupling with different inorganic 2D materials, blending into polymeric composites. The main physical and chemical properties of all the considered heterostructures and as‐realized derivatives of 2D bP, with a particular focus on the increase of stability in air, are described. Finally, the functional characteristics of each system which are correlated to and involved in the development of specific real‐setting applications, spanning from catalysis, to electronics and optoelectronics, to energy conversion and storage and biodiagnostics, are highlighted. [ABSTRACT FROM AUTHOR]

According to the local hard‐soft acid – base (HSAB) principle, the generalized local softness has been investigated based on the electrophilic reactions of H2O, HF, HCl and HBr to alkenes, and the effect of the softness on the chemical reactivity was studied in terms of the ab initio and atom‐bond electronegativity equalization method plus σπ (ABEEM‐σπ) method. Studies show that the finite difference approximation with ab initio method cannot always be used to predict the regioselectivity of the investigated reactions in terms of the local HSAB principle. But ABEEM‐σπ model could well describe chemical reactivity according to the local HSAB principle. A significant characteristic of the ABEEM‐σπ method is that the double bond is explicitly considered and partitioned. The square sums of differences of the local softness of the reaction center atoms, that is, Δs, or ΔSG with the generalized local softness and ∆sχ with the electronegativity, have been studied on the considered electrophilic additions. Studies indicate that ΔSG can be utilized not only to predict regioselectivity rules but also to rationalize the chemical reactivity of these addition reactions, and the generalized local softness is more suitable for the investigation of chemical reactivity between two chemical species. [ABSTRACT FROM AUTHOR]

Ionic liquids and deep eutectic solvents are of growing interest as solvents for the resource‐efficient synthesis of inorganic materials. This Review covers chemical reactions of various deep eutectic solvents and types of ionic liquids, including metal‐containing ionic liquids, [BF4]−‐ or [PF6]−‐based ionic liquids, basic ionic liquids, and chalcogen‐containing ionic liquids. Cases in which cations, anions, or both are incorporated into the final products are also included. The purpose of this Review is to raise caution about the chemical reactivity of ionic liquids and deep eutectic solvents and to establish a guide for their proper use. [ABSTRACT FROM AUTHOR]

In this paper, the kinetics of acylation reaction of o‐phenylenediamine/p‐phenylenediamine and benzoic anhydride were determined in microreactors, respectively. A kinetic model was established, all kinetic parameters including reaction orders, reaction rate constants, pre‐exponential factors, and activation energies were acquired. Validation experiments showed experimental data fit well with calculated data at different reactant concentrations and residence times. The comparisons of the reaction rate constants and activation energies were summarized to show the difference of chemical reactivities of phenylenediamines. According to the calculation of the kinetic model, the optimized reaction conditions were listed to meet the monoacylation selectivity equal to 97.0%. [ABSTRACT FROM AUTHOR]

A simple composite scheme is presented and benchmarked against the 38 reactions in Truhlar's HTBH38/08 and NHTBH38/08 databases. Mean unsigned deviation (MUD) for the complete set of 68 independent barriers is 0.40 kcal mol−1, compared to 1.31 kcal mol−1 for G4 and 1.62 kcal mol−1 for the M06‐2X‐D3 method. The MUD of the new scheme on the barriers in the DBH24/08 subset (12 out of the 38 reactions in the other sets) is 0.27 kcal mol−1, better than that obtained at the expensive CCSD(T,full)/aug‐cc‐pCV(T+d)Z level (0.46 kcal mol−1) and comparable to the most exact (and costly) Wn calculations (MUD = 0.14 kcal mol−1). The method was further tested against a subset of reactions, for which the geometry and energies of all species were determined at the much more demanding CCSD(T)‐F12//pVQZ‐F12 level. The SVECV‐f12 procedure on this database results in RMSE and MUD values of only 0.21 and 0.16 kcal mol−1. [ABSTRACT FROM AUTHOR]

This paper presents a brief summary of the difficulty that resides in the definition of the elusive concept of local chemical hardness. We argue that a definition of local hardness should be useful to a reactivity principle and not just as a mere definition. We then continue with a formal discussion about the benefits and difficulties of using the Fukui potential, which is interpreted as an alchemical derivative (alchemical hardness), as descriptor of local hardness of molecules. Computational evidence shows that the alchemical hardness is at least as good a descriptor as the combination of other two well‐stabilized descriptors of local hardness, such as the Fukui function and grand canonical local hardness. Although our results are auspicious for the alchemical hardness as descriptor of local hardness, we finish by calling the attention of the community on the importance of discussing the raison d'être of a local hardness function and its main characteristics. We suggest that an axiomatic construction of local hardness could be they way of constructing a local hardness which is both useful and free of arbitrariness. [ABSTRACT FROM AUTHOR]

This work relates a unique one‐pot procedure to assembly novel 2‐pyrazolin‐5‐one derivative functionalized through an isocyanide based formal [4+1] cycloaddition. A new, unexpected multicomponent reaction occurred when a pyrazolone was condensed with an aldehyde, an isocyanide, and water or alcohol components. Nine novel molecules with an embedded alkyl carboxamide group were obtained in moderate yield. Surprisingly, an unforeseen orthoamide intermediate was isolated and characterized, proving the plausible mechanism for the opened imidate obtained by formal [4+1] cycloaddition. This one‐pot approach to pyrazolone derivatives functionalized with amides stands as a significant advance for preparing this class of molecules. [ABSTRACT FROM AUTHOR]

BACKGROUND: Skin cell walls modulate anthocyanin and tannin extraction from grape skins. However, relationships between the composition of alcohol‐insoluble cell wall solids (AIS) and extraction are still unclear. Our objectives were to characterize the impact of variety, berry size and ripeness on skin AIS composition (polysaccharides, proteins) and polyphenol extraction during maceration. RESULTS: Grape skin composition and its impact on polyphenol extraction was compared for two varieties – Carignan and Grenache – with skins of berries sorted according to their size and density. Extractions were performed under model wine‐like maceration conditions. Fresh skins had similar content of polymeric tannins, but strongly differed in their anthocyanin content (higher in Carignan and in the ripest berries) and composition (higher proportions in coumaroylated anthocyanins in Carignan). Anthocyanin extraction was proportionally much higher in Grenache, which was not just related to the Carignan's higher levels in coumaroylated anthocyanins. Chemical reactions decreased anthocyanin concentrations in solution for both varieties. Tannin extraction for Grenache was slightly higher and faster than for Carignan. Skin AISs differed slightly between the two varieties in their carbohydrate composition and protein content, but not between modalities. Polyphenol analyses in the precipitates evidenced at the end of the maceration and in residual skins highlighted differences between the two varieties and between berries with different ripeness. CONCLUSION: Structural information on the cell wall network and on its changes during maceration, along with a better understanding of the chemical reactions of anthocyanins and tannins, is needed to better relate grape and wine polyphenol composition. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Based on the quantum chemical topology of the modified electron localization function ELFx, an efficient and robust mechanistic methodology designed to identify the favorable reaction pathway between two reactants is proposed. We first recall and reshape how the supermolecular interaction energy can be evaluated from only three distinct terms, namely the intermolecular coulomb energy, the intermolecular exchange‐correlation energy and the intramolecular energies of reactants. Thereafter, we show that the reactivity between the reactants is driven by the first‐order variation in the coulomb intermolecular energy defined in terms of the response to changes in the number of electrons. Illustrative examples with the formation of the dative bond B‐N involved in the BH3NH3 molecule and the typical formation of the hydrogen bond in the canonical water dimer are presented. For these selected systems, our approach unveils a noticeable mimicking of Edual onto the DFT intermolecular interaction energy surface calculated between the both reactants. An automated reaction‐path algorithm aimed to determine the most favorable relative orientations when the two molecules approach each other is also outlined. [ABSTRACT FROM AUTHOR]

Bone tissue engineering is gaining popularity as an alternative method for the treatment of osseous defects. A number of biodegradable polymers have been explored for tissue engineering purposes. A new family of biodegradable polymer/bioactive glass composite materials has been designed to be used in bone regeneration approaches. In this work, a hybrid scaffold of chitosan (CH) and bioactive glass nanoparticles (BGN) was prepared by the freeze‐gelation method. This method has been studied by adjusting the concentration of acetic acid; this process can influence the structure properties of the scaffold. In this work, several BGN/CH composites have been prepared by varying the proportion of BGN in the hybrid scaffold (20, 40, 60, and 80%). Brunauer–Emmett–Teller results showed the increased surface area and porosity volume of our composite with decreasing BGN proportion. BGN/CH hybrid scaffold was characterized by using physicochemical techniques. Obtained results showed a macroporous morphology of the scaffold with a pore size of about 200 μm, and a homogeneous distribution of the BGN in the CH matrix. X‐ray diffraction study confirmed the amorphous state of the BGN/CH hybrid scaffold. Interaction between CH and BGNs in the composite was confirmed. The in vitro assays showed adequate degradation properties, which is essential for the potential replacement by the new tissue. The in vitro bioactivity studies confirmed the formation of an apatite layer on the surface of the hybrid scaffold, which results in a direct bone bonding of the implant. These results indicate that BGN/CH hybrid scaffold developed is a potential candidate for bone tissue engineering. [ABSTRACT FROM AUTHOR]

We discuss an extension of the venerable Parr‐Pearson parabolic charge transfer model that explicitly includes 3rd order effects. We then use this new model to provide new arguments supporting the validity of Parr and Yang's "|Δμ| big is good" (DMB) principle. Additionally, we show how to re‐derive this principle from the Parr‐Pearson parabolic model, using simpler arguments than those presented in our previous proof of the DMB rule. [ABSTRACT FROM AUTHOR]

The corrosion behaviors of high oxide ion conductors using solid oxide membrane (SOM) electrolysis were investigated in practical operating conditions (current load or molten CaF2‐NaF‐CaO eutectic salt). In previous researches, yttria‐stabilized zirconia (YSZ), which is widely used in SOM electrolysis due to its good mechanical properties and ionic conductivity at high temperature, has several problems including phase transition due to yttrium ion dissolution, which results in decreased current efficiency and severe fracture of SOM tube. Thus, we introduced oxide ion conductors with a higher ionic conductivity than that of YSZ to exploit its excellent current efficiency and long‐term stability. In this study, we investigated the phase stability of Sr‐ and Mg‐doped lanthanum gallate (LSGM), Sc‐doped zirconia (ScSZ) and Gd‐doped ceria (GDC) using the structural analysis methods. Phase transition of LSGM and ScSZ easily occurred than that of GDC. GDC showed fairly tolerable stability; the molten salt ions were found only 10 μm deep on the surface, and the ions hardly penetrated the interior of bulk. However, LSGM (~40 μm) and ScSZ (~100 μm) showed a deep cation ion infiltration depth from the surface and severe surface corrosion was observed on the surface of LSGM and ScSZ. [ABSTRACT FROM AUTHOR]

Application of Alpha‐oscillator theory to quantum electrodynamics (QED) solves the mystery (Feynman) of the double‐slit phenomenon involved in the foundation of quantum mechanics (QM). Even if with the same initial condition given, different spots on the screen can be predicted deterministically with no introduction of hidden variables. The interference pattern is similar to, but cannot be reproduced quantitatively by, that of the QM wave function, contrary to many‐years‐anticipation: a new prediction, awaiting experimental test over and above the Bohr–Einstein gedanken experiment. The general proof has already been published in Ref. [3a] and the concrete numerical algorithm of the extended normal mode technique for concrete trajectory of one electron in Ref. [3b]. In this article, (1) the new "interpretation" of the QED wave function is given in section "Interpretation of Wave Function in QED": the QED wave function used in the extended normal mode technique gives probability density distribution function of the initial values of trajectories. Moreover, (2) for the sake of demonstration of this new interpretation, the time‐independent stationary state QM wave function is substituted to the QED wave function in section "Internal Self‐Stress of Energetic Particles": the QED wave function is realized by internal self‐stress revealed as energy density at the initial conditions. The renewed energy density is applied to study a unified scheme for generalized chemical reactivity. This is a new kind of chemical force acting in between electrons not in between nuclei. This paves a way for more advanced time‐dependent simulation of electronic structure and dynamics in chemical reaction dynamics by tracing trajectories of many electrons. © 2018 Wiley Periodicals, Inc. (a) Initial positions a→tii=1,2.... in the double‐slit phenomenon are confined in a small domain Ωr→r→=a→tii=1,2.... of the first slit. (b) As to one trajectory in finite volume, if ergodicity of trajectory is not assumed, then the consecutive points are sparsely distributed for Ωr→r→=a→tii=1,2.... even on the putative isosurface of wave function Φ˜αiti=const. [ABSTRACT FROM AUTHOR]

Process safety management (PSM) of hazardous chemicals is a core tenet of the chemical, oil, and gas industries. Organizations in these industries have increasingly woven the elements of PSM into their strategic vision, day‐to‐day operations, and interactions with contractors and vendors. This cultural evolution has, in part, been driven by major accidents in these fields. In these industries, the chemicals, their hazardous properties, and their potential interactions, are usually either well‐defined or capable of being well‐defined. Control and mitigation strategies for those chemicals can be developed based on this available knowledge. In contrast, companies that handle wastes have experienced catastrophic accidents due to the ill‐defined nature of the hazards. This industry handles the cast‐offs, dregs, and refuse, which makes identification of the hazards and prevention of incidents more challenging. How do you implement a PSM program when your input streams can vary due to processes at a plant you do not control or monitor? Does the Environmental Protection Agency (EPA) Resource Conservation and Recovery Act (RCRA) provide sufficient guidance of safely handling of wastes? The overriding theme in the incidents is that PSM is more complex to apply to unknown, mixed, and uncontrolled chemicals, both solid and liquid. To assist companies that handle wastes, this paper provides several case studies of fires and explosions involving multiple waste material handling processes at different facilities. The incidents involved numerous matrices from solid industrial wastes, EPA RCRA hazardous wastes, to waste solvents. An analysis of the lessons learned will be presented and used to provide realistic guidelines to reduce safety risks based on a pragmatic implementation of process safety management principles. The paper will also compare OSHA (Occupation Safety and Health Administration) PSM with EPA RCRA approaches to characterizing wastes versus managing the hazards, and will emphasize those elements that played critical roles in the accident case studies. © 2018 American Institute of Chemical Engineers Process Process Saf Prog 37:427–441, 2018 [ABSTRACT FROM AUTHOR]

The value of the molecular electrostatic potential minimum (Vmin) and its topographical features (position, as well as the eigenvalues and eigenvectors of the corresponding Hessian matrix) are recently proposed as the criteria for characterizing a lone pair (Kumar A. et al., J. Phys. Chem. 2014, A118, 526). This electrostatic characterization of lone pairs is examined for a large number of small molecules employing MP4/6‐311++G(d,p)//MP2/6‐311++G(d,p) theory. The eigenvector of the Hessian matrix corresponding to its largest eigenvalue (λmax), is found to be directed toward the lone pair‐bearing‐atom, with λmax showing a strong linear correlation with Vmin. Large magnitudes of Vmin and λmax indicate a charge‐dense lone pair. The topographical features of Vmin are seen to provide insights into the interactive behavior of the molecules with model electrophiles, viz. HF, CO2, and Li+. In all the complexes of HF and majority of the other complexes, the interaction energy (Eint) correlates well with the respective Vmin, value, but for some deviations occurring due to other competing secondary interactions. The electrostatic interactions are found to be highly directional in nature as the orientation of interacting atom correlates strongly to the position of lone pair. In summary, the present study on a large number of test molecules shows that electrostatics is able to probe lone pairs in molecules and offers a simple interpretation of chemical reactivity. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Green synthesis of silver nanoparticles (AgNPs) using Shivlingi (Bryonia laciniosa) seed extract was carried out. Characterisation of synthesised nanoparticles was accomplished through the optical absorption and photoluminescence spectrum, X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The XRD analysis further confirmed the size of nanoparticles ∼15 nm. TEM images revealed homogeneous spherical ∼10 nm Bryonia extract capped AgNPs. The biological studies indicated that both Bryonia seed extract and the nanoparticles lack anti‐microbial activity; however, the nanoparticles had better cytotoxicity and total antioxidant activity. The Lethal concentration (LC)50 value of water extract and the nanoparticles were found to be 1091 and 592 μg/ml, respectively. The lower LC50 of nanoparticles indicates that it is more cytotoxic than the crude extract. The results indicate that the Bryonia seed is safe to be used as a medicine and the formation of their nanoparticle has further enriched the chemical reactivity, energy absorption and biological mobility. [ABSTRACT FROM AUTHOR]

The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction energies between the two distorted molecules. The energy required to distort the molecules is called the activation strain or distortion energy. This energy is the principal contributor to the activation barrier. The transition state occurs when this activation strain is overcome by the stabilizing interaction energy. Following the changes in these energies along the reaction coordinate gives insights into the factors controlling reactivity. This model has been applied to reactions of all types in both organic and inorganic chemistry, including substitutions and eliminations, cycloadditions, and several types of organometallic reactions. [ABSTRACT FROM AUTHOR]

The prediction of reactivity is one of the long-standing objectives of chemistry, contributing to enforce the link between theory and experiment. In particular, the regioselectivity of aromatic molecules has motivated the proposal of different reactivity descriptors based on foundational theories, like Frontier Molecular Orbital (FMO) theory and density functional theory, to predict and rationalize such regioselectivity. This article examines cases where reactivity descriptors, based on FMO theories, are known to have failed, specifically on electrophilic aromatic substitution reactions, through a simple but effective new reactivity model: the Orbital-weighted Fukui function ( [ABSTRACT FROM AUTHOR]

In this Focus Review, we present the application of the so-called Activation Strain Model of chemical reactivity to the Diels-Alder cycloaddition reaction. To this end, representative recent examples have been selected to illustrate the power of this new computational approach to gain a deeper quantitative understanding of this fundamental process in chemistry. We cover a wide range of issues, such as, the ' endo-rule', reactivity trends emerging from systematic variation in the reactants' strain, and cycloaddition reactions involving relevant species in material science, that is, fullerenes, polycyclic aromatic hydrocarbons and nanotubes. [ABSTRACT FROM AUTHOR]

A brief overview of the work in the research group of the present author on extracting knowledge from chemical reaction data is presented. Methods have been developed to calculate physicochemical effects at the reaction site. It is shown that these physicochemical effects can quite favourably be used to derive equations for the calculation of data on gas phase reactions and on reactions in solution such as aqueous acidity of alcohols or carboxylic acids or the hydrolysis of amides. Furthermore, it is shown that these physicochemical effects are quite effective for assigning reactions into reaction classes that correspond to chemical knowledge. Biochemical reactions constitute a particularly interesting and challenging task for increasing our understanding of living species. The BioPath.Database is a rich source of information on biochemical reactions and has been used for a variety of applications of chemical, biological, or medicinal interests. Thus, it was shown that biochemical reactions can be assigned by the physicochemical effects into classes that correspond to the classification of enzymes by the EC numbers. Furthermore, 3D models of reaction intermediates can be used for searching for novel enzyme inhibitors. It was shown in a combined application of chemoinformatics and bioinformatics that essential pathways of diseases can be uncovered. Furthermore, a study showed that bacterial flavor-forming pathways can be discovered. [ABSTRACT FROM AUTHOR]

Screening of the change mechanism of salicylic acid-4,4′dipyridyl (SAA-4,4′dipy) cocrystals to acetyl salicylic acid-4,4′dipyridyl (ASA-4,4′dipy) cocrystals was performed and their transformation investigated. Cocrystals of SAA-4,4′dipy are concomitantly formed in ASA/4,4′dipyridyl/ethanol solutions, resulting from ASA decomposition. Eventually, cocrystals of ASA-4,4′dipy are obtained from a sequence of in situ reactions by controlling the operating conditions. Both cocrystals have the same hydrogen bonding interaction between the drug molecules. The ketene functional group decomposed in salicylic acid cocrystal formation reaggregates during solution-mediated cocrystallization that leads to the formation of ASA cocrystals. [ABSTRACT FROM AUTHOR]

This article presents a personal view of the field of physical organic chemistry (broadly construed), its history, its current status, and what it may become in the future. [ABSTRACT FROM AUTHOR]

Despite the promulgation of the "PSM Standard" by OSHA in 1992, chemical accidents continue to occur at an alarming rate. As part of the process safety information element of the standard, OSHA requires reactivity data on the chemicals in the process. One piece of this reactivity data is a chemical interaction matrix. Several software programs provide simple approaches to generating these interaction charts for common materials using assigned reactive groups. If your process involves materials not included, you are left to determine the reactivity and incompatibilities on your own. This paper will explain a process for assigning reactive groups using chemical classification and structural analysis. This process can be used for less commonly understood materials such as additives, lubricants, mixtures, products, etc. that may come into contact with process chemicals. [ABSTRACT FROM AUTHOR]

The title compound ( 1), 4-(1-benzyl-5-methyl-1 H-1,2,3-triazol-4-yl)-6-(2,4-dichlorophenyl)pyrimidin-2-amine (C20H16Cl2N6), was synthesized and structurally characterized by elemental analysis, 1H NMR and 13C NMR and single crystal X-ray diffraction. The compound crystallizes as a colourless needle shaped in the triclinic system, space group P-1 with cell constants: a = 10.7557(11) Å, b = 12.7078(17) Å, c = 15.511(2) Å, α = 68.029(4) 0, β = 86.637(5) 0, γ = 87.869(4) 0; V = 1962.4 (4) Å3, Z = 4. There are two structurally similar but crystallographically independent molecules (A and B) in the asymmetric unit of the title compound, which is linked via N-H...Cl hydrogen bond. An intramolecular C-H...N hydrogen also occurs in each molecule. In the crystal, each of independent molecules forms a centrosymmetric dimer with an R22(8) ring motifs through a pair of N-H...N hydrogen bonds. These dimers are further connected by intermolecular N-H...Cl and C-H...Cl hydrogen bonds, forming an infinite two dimensional supramolecular network lying parallel to the [010] plane. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G (d, p) basis set and compared with the experimental data. Mulliken population analyses on atomic charges, HOMO-LUMO energy levels, Molecular electrostatic potential and chemical reactivity of the title compound were investigated by theoretical calculations. The thermo dynamical properties of the title compound at different temperature have been calculated and corresponding relations between the properties and temperature have also been obtained. The in vitro antibacterial activity has been screened against Gram-positive ( Bacillus cerus and Staphylococcus epidermidis) and Gram-Negative ( Escherichia coli, Acinetobacter baumannii and Proteus vulgaris). The results revealed that the compound exhibited good to moderate antibacterial activity. [ABSTRACT FROM AUTHOR]

In this work, quantum chemistry calculations performed to study the kinetics and thermodynamic parameters of [2+2] cycloaddition reaction of diethyl azodicarboxylate and ethyl vinyl ether in eighty-three solvents and gas phase. The solvent effect on the reaction path and electron density of the C2N6 critical bond as the reaction coordinate at the TS was investigated. Calculated rate constants in various solvents showed that increase in the activation dipole moment accelerates the reaction. Based on the time-dependent studies, using a conductor like polarizable continuum model solvation model, the solvent effects on the excitation energies of the reactants and transition states (TSs) and the corresponding chemical shifts were analyzed. Finally, some correlations between the rate constant and quantum reactivity indices such as electrophilicity index, chemical hardness, and electronic chemical potential were investigated. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This study shows that the chemical reactivities depend on the orbital energy gaps contributing to the reactions. In the process where a reaction only makes progress through charge transfer with the minimal structural transformation of the reactant, the orbital energy gap gradient (OEGG) between the electron-donating and electron-accepting orbitals is proven to be very low. Using this relation, a normalized reaction diagram is constructed by plotting the normalized orbital energy gap with respect to the normalized intrinsic reaction coordinate. Application of this reaction diagram to 43 fundamental reactions showed that the majority of the forward reactions provide small OEGGs in the initial stages, and therefore, the initial processes of the forward reactions are supposed to proceed only through charge transfer. Conversely, more than 60% of the backward reactions are found to give large OEGGs implying very slow reactions associated with considerable structural transformations. Focusing on the anti-activation-energy reactions, in which the forward reactions have higher barriers than those of the backward ones, most of these reactions are shown to give large OEGGs for the backward reactions. It is also found that the reactions providing large OEGGs in the forward directions inconsistent with the reaction rate constants are classified into S N2, symmetric, and methyl radical reactions. Interestingly, several large-OEGG reactions are experimentally established to get around the optimum pathways. This indicates that the reactions can take significantly different pathways from the optimum ones provided no charge transfer proceeds spontaneously without the structural transformations of the reactants. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this work, we applied the theory of Atoms in Molecules to the study of carbocationic transition states involved in two different reaction mechanisms, using the proposed mechanism of ethylene dimerization over Brønsted-acid site of zeolite catalyst as a study case. We report the main results of the analysis of the Laplacian of electron density distribution and Bader's atomic charges to increase our understanding of stereoelectronic aspects of these chemical reactions. At B3LYP/6-31++G(d,p)//B3LYP/6-3G(d,p) level, our results show that the envelopes of Laplacian distribution provide valuable information about the relative orientation of the species involved in the reaction, their interaction with the catalyst surface, and its stability. The stabilization and formation of these transition states depend on the availability of electrons in the environment. Such availability plays a key role to stabilize the positive charge on the carbocationic center and, thus, to stabilize the formed carbocation. The analysis of envelopes of Laplacian could be used to study different organic and inorganic chemical reactions and provide new insights to increase our understanding of these chemical reactions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT A Bayesian integrated testing strategy (ITS) approach, aiming to assess skin sensitization potency, has been presented, in which data from various types of in vitro assays are integrated and assessed in combination for their ability to predict in vivo skin sensitization data. Here we discuss this approach and compare it to our quantitative mechanistic modeling (QMM) approach based on physical organic chemistry. The main findings of the Bayesian study are consistent with our chemistry-based approach and our previously published assessment of the key determinants of sensitization potency, in particular the relatively high predictive value found for chemical reactivity data and the relatively low predictive value for bioavailability parameters. As it stands at present the Bayesian approach does not utilize the full range of predictive capability that is already available, and aims only to assign potency categories rather than numerical potency values per se. In contrast, for many chemicals the QMM approach can already provide numerical potency predictions. However, the Bayesian approach may have potential for those chemicals where a chemistry modeling approach cannot provide a complete answer (e.g. pro-electrophiles whose in cutaneo activation cannot currently be modeled confidently). Nonetheless, our main message is of the importance of leveraging chemistry insights and read-across approaches to the fullest extent possible. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The accurate prediction of rate constants for chemical reac-tions in solution, using computational methods, is a challeng-ing task. In this work, a computational protocol designed to be a reliable tool in the study of radical-molecule reactions in solution is presented. It is referred to as quantum mechanics-based test for overall free radical scavenging activity (QM-ORSA) because it is mainly intended to provide a universal and quantitative way of evaluating the free radical scavenging activity of chemical compounds. That is, its primary antioxidant activity. However, it can also be successfully applied to obtain accurate kinetic data for other chemical reactions in solution. The QM-ORSA protocol has been validated by comparison with experimental results, and its uncertainties have been pro-ven to be no larger than those arising from experiments. Fur-ther applications of QM-ORSA are expected to contribute increasing the kinetic data for free radical-molecule reactions relevant to oxidative stress, which is currently rather scarce. [ABSTRACT FROM AUTHOR]

Paper spray ionization can be used to study organic reactions in solution under ambient conditions by utilizing the rate acceleration that occurs in reactions in small volumes of solution. In this novel approach to performing reactions, reagents are transferred onto a triangular paper surface by drop-casting and charged droplets of the reaction product mixture are released by field evaporation and examined online by mass spectrometry. The increase in the rate of product formation is attributed to solvent evaporation, which increases reagent concentrations, changes the pH, and enhances intermolecular interactions. As a proof of principle, the Katritzky reaction between a pyrylium salt and mono- or diamines, including substituted anilines, was investigated. The influence of electronic and steric effects was evaluated straightforwardly. The carbon chain length of α,ω-diamines was found to control the formation of mono- versus disubstituted products, thus reflecting the strong destabilizing coulombic effects in the shorter carbon-chain systems. Information on the mechanism was provided by the observation of 2 H-pyran intermediates and mixed pyridinium-2 H-pyran ions. The rates of product formation in the base-assisted Katritzky reaction increase linearly from 0.1 to 10 equivalents of triethylamine. The reactive paper spray technique, owing to its speed and information content, has potential pedagogical value and provides a tool to explore organic reactions and correlate experimental results with current mechanistic understanding. [ABSTRACT FROM AUTHOR]

The ability of substituted boranes, X nBH3− n, to form stable complexes with the hydrogen molecule is analyzed by making use of computational chemistry and local reactivity parameters. In these complexes, the hydrogen molecule acts as a Lewis base while the borane moiety is the Lewis acid. Electronegative groups (X = CF3, F, OH) are selected to increase the acidity of the borane and it is found that the energetic stability of the complexes is only increased for the trifluoromethyl-substituted Lewis acids, at the MP2/6-311++g(3df, 3pd) level. It is also found that the BLYP density functional underestimates the adduct stability of these species. On the other hand, fluoroboranes and hydroxyboranes do not form donor-acceptor adducts with the hydrogen molecule; instead, we find weakly bounded van der Waals complexes. Additional features on the intrinsic reactivity of boranes are analyzed with the molecular electrostatic potential and the acceptor Fukui function. The nature of the interaction among the boranes and the hydrogen molecule is explored by using the topological analysis of the electron density through the Bader's Atoms-in-Molecules theory. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Using gradient-corrected density functional theory, we have comparatively studied the adsorption properties of diatomic molecules N2 and NO on vanadium clusters up to 13 atoms. Spontaneous dissociation is found for N2 adsorbing on V n with n = 4-6, 12, and for NO with n = 3-12, respectively, whereas for the rest of the clusters, N2 (NO) molecularly adsorbs on the cluster for all the possible sites. The incoming N2 retains the magnetism of V n except for V2 and V6 whose moments are quenched from 2 μB to zero. Consequently, the moments of V nN2 ( n = 2-13) show even/odd oscillation between 0 and 1 μB. On the adsorption of NO, the magnetic moments of V n with closed electronic shell are raised to 1 μB at n = 4, 8, and 10, and 3 μB at n = 12, whereas for open shell clusters, their magnetic moments increase for n = 5 and 9 and decrease for n = 2, 3, 5-7, 11, and 13 by 1 μB. These findings are rationalized by combinatory analysis from several aspects, for example, the geometry and stability of bare clusters, charge transfer induced by the adsorption, feature of frontier orbitals, and spin density distribution. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A surprising number of process incidents occur due to a lack of general understanding of process hazards and lack of basic hazards assessment, subsequently resulting in the absence of or inadequate Process Hazards Analysis (PHA) to provide appropriate safeguards for minimizing process risks. Comprehensive assessment of intrinsic hazards that are present in a chemical process or facility is one of the first steps necessary in documenting process safety information and technology prior to conducting PHAs and requires much more than, for example, just a review of the material safety data sheets of materials used in the process. This article reviews practical approaches for conducting and documenting intrinsic hazards assessments. © 2012 American Institute of Chemical Engineers Process Saf Prog, 2012 [ABSTRACT FROM AUTHOR]

Chemical reactivity descriptors are derived within the framework of the pair density functional theory. These indices provide valuable information about bonding rearrangements and activating mechanisms upon electrophilic or nucleophilic reactions. Indices derived and tested in this work represent nonlocal counterparts of the local reactivity indices derived in the context of conceptual density functional theory (CDFT) and frequently used in reactivity studies; the Fukui function, the local softness and the dual descriptor. In this work, we show how these nonlocal indices provide a quantum chemical basis to explain the success of qualitative resonance models in chemical reactivity predictions. Also, local information is implicitly contained as CDFT indices are obtained by simple integration. As illustrative examples, we have considered in this work the Markovnikov's rule, the reactivity of enolate anion, the nucleophilic conjugate addition to α,β-unsaturated compounds and the electrophilic aromatic substitution of benzene derivatives. The densities used in this work were obtained with Hartree-Fock, Kohn-Sham DFT, and singles and doubles configuration interaction (CISD) approaches. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The reactive behavior of GABA and its agonist molecules have been investigated using B3LYP hybrid density functional method at the 6-311++G** basis set level, in the gas phase and dielectric media. The calculations have been performed to obtain optimized geometries, relative energies, net atomic charges, HOMO, and LUMO energies. Solvent effects have been analyzed using isodensity polarized continuum model (IPCM) for four different solvents, which are chloroform, ethanol, DMSO, and H2O. The results have suggested that both the amino group and carboxyl group have been two of the most important active site for interactions between all compounds and their receptors. In addition they have suggested that the amino group reflects the difference in biological activity for each all molecules. The structures of these agonists have provided an essential foundation for subsequent structure-activity analysis of ligand binding at GABA receptors, neuronal uptake inhibitors and transporters. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

The reactive behavior of acetylcholine and its agonist molecules have been investigated using B3LYP hybrid density functional method at the 6-311++G** basis set level, in the gas phase and aqueous phase. The calculations have been performed to obtain optimized geometries, relative reactivities, net atomic charges, HOMO, and LUMO energies. The solvent effect has been analyzed by using the continuum model (IPCM) and, the obtained results have shown that the all molecules have been stabilized more by solvent dielectric constant. For Ach and its analogues, it has been very well known that esteratic site and quaternary ammonium group which have reflected the difference in biological activity have been the two of the most important active site for interactions between molecule and its receptor. The structures of these analogues have provided an essential foundation for subsequent structure-activity analysis of ligand binding at acetylcholine receptors, neuronal uptake inhibitors and transporters. Molecular modeling predictions will be important initial steps toward the development of novel pharmaceuticals in the fight acetylcholine-related neurological disorders. This work is therefore expected to facilitate the design and development of new biologically active Ach analogues to treat Ach-related neurological disorders and, specially is used to qualitative understanding of the reactivity and related properties and, so on can be used to a preselection of new ligands which at the moment is taken essentially from empirical knowledge. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]