Types Of Reactions Research Articles

Decoupling Degradation at the Electrode Interfaces in Prussian White Full Cells

AbstractPrussian blue analogues for sodium‐ion battery cathodes are growing in popularity as next‐generation energy storage devices. Prussian White (PW) with formula NaxFe[Fe(CN)6]y•nH2O is leading the trend, having already been commercialized. However, capacity fade (PW/electrolyte degradation) and safety concerns (cyanide/cyanogen release) still raise concerns. Online electrochemical mass spectrometry, supported by both operando Fourier transform infrared spectroscopy and Mössbauer spectroscopy, is herein used to analyze degradation processes in PW‐based Na‐ion full cells. Apart from the typical cell formation reactions, hydrogen is observed to evolve during cell discharge and evidenced to stem from oxidation of NaH, accumulated upon charge. Over‐oxidation of PW after full desodiation releases CN, which not only forms (CN)2 but also degrades the electrolyte. Loss of CN likely results in a nanometric (≈4 nm) surface‐reconstructed passivation layer on PW, thus inhibiting further degradation. Fundamental understanding of degradation reactions in PW full‐cells, as gathered herein, shows that the aforementioned capacity fade and safety concerns are wholly addressable and hence guides the further development of Na‐ion batteries for wider ranges of applications.

Synthesis of Trifluoromethylthio Compounds from Sulfur Containing Precursors

The trifluoromethylthio group (–SCF3) exhibits several distinctive physicochemical properties and can alter the molecular lipophilicity and other pharmacokinetic properties of functional molecules. Moreover, its potent electron‐withdrawing capability confers enhanced metabolic stability to functional molecules. Molecules containing trifluoromethylthio groups are extensively applied in the synthesis of pharmaceuticals or agrochemicals and have garnered significant attention in recent years. The synthetic routes to trifluoromethylthio groups primarily fall into two categories: direct introduction of –SCF3 into target molecules, and indirect construction of –SCF3 through the introduction of –CF3 into sulfur containing precursors. In this review, we delineate approaches developed over the past seven years for the indirect construction of SCF3 groups via electrophilic, nucleophilic, radical, or other types of reactions involving –CF3 groups and sulfur‐containing precursors. These reactions are classified into seven categories depending on the employed: thiols, disulfides, thiosulfates, sodium sulfinates, sulfonyl chlorides, sulfoxides, and other sulfur‐containing precursors.

Cities against authoritarianism? Polish and Hungarian capitals facing centralistic pressure

ABSTRACT The paper provides a new taxonomy of local government reactions to the recentralization policies of authoritarian central governments. By studying the capitals of two Central European countries recently undergoing an illiberal turn – Budapest and Warsaw – we have extended the list of reaction types previously identified in the literature. Moreover, the comparative nature of the research has highlighted the internal diversity of reaction types and allowed us to hypothesize on the sources of the differences between Hungary and Poland. These differences are rooted in the initial level of decentralization, municipal networking and the political and legal framework.

How Accurate Are QM/MM Models?

Despite the success and widespread use of QM/MM methods in modeling (bio)chemically important processes, their accuracy is still not well understood. A key reason is because these methods are ultimately approximations to direct QM calculations of very large systems, which are impractical to perform in most cases. We highlight recent progress toward the development of realistic model systems where it is possible to obtain full QM reference data to directly and systematically evaluate the effectiveness of different QM/MM generation schemes. These model systems are highly flexible and can be tailored to probe the sensitivity of a QM/MM model to different reaction types and simulation parameters such as pairing of QM and MM potentials, QM region size, and composition. It is envisaged that this strategy could be used to directly validate different QM/MM generation schemes and spur the development of more robust models in the future.

A prescription for engineering PFAS biodegradation.

Per- and polyfluorinated chemicals (PFAS) are of rising concern due to environmental persistence and emerging evidence of health risks to humans. Environmental persistence is largely attributed to a failure of microbes to degrade PFAS. PFAS recalcitrance has been proposed to result from chemistry, specifically C-F bond strength, or biology, largely negative selection from fluoride toxicity. Given natural evolution has many hurdles, this review advocates for a strategy of laboratory engineering and evolution. Enzymes identified to participate in defluorination reactions have been discovered in all Enzyme Commission classes, providing a palette for metabolic engineering. In vivo PFAS biodegradation will require multiple types of reactions and powerful fluoride mitigation mechanisms to act in concert. The necessary steps are to: (1) engineer bacteria that survive very high, unnatural levels of fluoride, (2) design, evolve, and screen for enzymes that cleave C-F bonds in a broader array of substrates, and (3) create overall physiological conditions that make for positive selective pressure with PFAS substrates.

Theoretical Study of the Dissociative Recombination and Vibrational (De-)Excitation of HCNH and Its Isomers by Electron Impact+

Protonated hydrogen cyanide, HCNH+, is one of the most important molecules of interest in the astrophysical and astrochemical fields. This molecule not only plays the role of a reaction intermediary in various types of interstellar reactions but was also identified in Titan’s upper atmosphere. The cross sections for the dissociative recombination (DR) and vibrational (de-)excitation (VE and VDE) of HCNH+ and its CNH2+ isomer are computed using a theoretical approach based on a combination of the normal mode approximation for the vibrational states of the target ions and the UK R-matrix code to evaluate electron-ion scattering matrices for fixed geometries of ions. The theoretical convoluted DR cross section for HCNH+ agrees well with the experimental data and a previous study. It was also found that the DR of the CNH2+ isomer is important, which suggests that this ion might be present in DR experiments of HCNH+. Moreover, the ab initio calculations performed on the H2CN+ isomer predict that this ion is a transition state. This result was confirmed by the study of the reaction path of the HCNH+ isomerization that was carried out by evaluating the intrinsic reaction coordinate (IRC). Finally, thermally averaged rate coefficients derived from the cross sections are provided for temperatures in the 10–10,000 K range. A comprehensive set of calculations is performed to assess the uncertainty of the obtained data. These results should help in modeling non-LTE spectra of HCNH+, taking into account the role of its most stable isomer, in various astrophysical environments.

Au-Catalyzed 5C Reaction of Type II Diene-Ynenes toward Dihydrosemibullvalenes: Reaction Development and Mechanistic Study.

We report an unexpected gold-catalyzed 5C reaction of type II diene-ynenes to synthesize dihydrosemibullvalenes, which are potential bioisosteres for drug discovery. This 5C reaction occurs through a sequence of elementary reactions of cyclopropanation/Cope rearrangement/carbon shift/cyclopropanation/C-H insertion (shortened here as the 5C reaction), supported by quantum chemistry calculations. Mechanistic studies have also been applied to answer why type-II diene-ynenes cannot access seven-membered carbocycles-embedded bridged molecules under the gold catalysis, finding that the chair-like Cope rearrangement transition state (not the traditional boat-like transition state) is the key to the change of regiochemistry.

Inverse Electron Demand Diels-Alder Reaction of Pyrazines with 2,5-Norbornadiene as Acetylene Precursor

Herein, we report the reaction of pyrazines with 2,5-norbornadiene, an acetylene precursor, as a cascade of Diels-Alder reactions yielding substituted pyridines. In contrast to the known examples of intermolecular Diels-Alder type reaction of pyrazines with acetylene, which usually leads to a mixture of products, in our case the formation of a single isomer was observed. The proposed approach allows the conversion of pyrazines with different types of substitution, except those containing methyl and amino donor groups, to pyridines. In addition, highly functionalized aminonicotic esters were obtained, which can be used for the synthesis of bioactive compounds. An unusual course of the Diels-Alder reaction was found in the case of tetrasubstituted pyrazines, which cleave organic nitriles instead of HCN. Quantum-chemical modeling of possible transition states showed that this Diels-Alder reaction proceeds via cycloaddition of 2,5-norbornadiene to pyrazine with sequential elimination of HCN and cyclopentadene; the reaction pathway including initial formation of acetylene from norbornadiene and subsequent Diels-Alder reaction with the acetylene was rejected as kinetically unfavorable.

A systematic study of disclination-induced internal stress associated with multiple types of twin-twin reactions in Mg alloys: analytical solutions and numerical calculations

Deformation twinning plays an important role in enhancing the mechanical properties of metals and alloys by mechanisms such as twinning-induced plasticity and strain hardening. However, internal stress concentration associated with the interactions and reactions of twins may also lead to the degradation of ductility and fracture toughness. While the elastic behavior of individual twin types has been extensively studied, the crystallographic reactions among multiple types of twins have not been well recognized, which could produce high-index or irrational twins as well as byproduct disclinations. A theoretical framework to predict twin-twin reaction products and quantify associated internal stress is still unavailable. Here we suggest a general approach to investigate twin-twin reactions through symmetry-dictated characteristic defect analyses and stress field calculations based on disclination theory. By using Mg as an example, a systematic study of multiple types of twin-twin reactions has been conducted. The product defects arising from the reactions and associated internal stress fields have been determined analytically, which are validated by numerical simulations and experimental measurements. This work not only establishes a theoretical foundation for quantifying defect-induced internal stress concentration from complicated twin-twin interactions/reactions, but also offers new insights into the impact of deformation twins on mechanical properties.

Integrated in situ spectroscopic characterization of bi-functional nanoporous hybrid catalysts

Bi-functional catalysts possess various catalytic sites and can catalyze different types of reactions in a single-pot cascade manner. Herein, we report the synthesis and characterization of mono- and bifunctional silica-based mesoporous hybrid catalysts involving acid and base active sites. The ability for cooperative catalysis has been investigated using a multi-technique approach involving powder X-ray diffraction, FT-IR, and multinuclear MAS NMR spectroscopy, as well as thermogravimetric analysis. To elucidate the nature and strength of multifunctional catalytic sites, different types of probe molecules were employed and studied using spectroscopic techniques. The results show that the activity of the mesoporous surface-grafted acid and/or base sites is directly related to the intimacy criterion, the separation between the different types of catalytic sites. The presence or absence of mutual interactions between the different catalytic sites dictates the selectivity and yield of the reactions.

Reactions and Biological Activities of Hydrazonoyl Halides.

This review covers the literature information on the chemistry of hydrazonoyl halides with different substrates to give heterocyclic compounds. From the foregoing survey, it seems this provides a useful and convenient strategy for the synthesis of numerous heterocyclic derivatives. The subject of such reactions is still ongoing and undoubtedly will provide new fused functionalized compounds of both industrial and biological interest. A literature survey revealed that a great deal of interest has been focused on the synthesis of functionalized heterocyclic compounds due to their wide range of biological activities, such as contact dermatitis, anthelmintic, antiviral, antimicrobial, herbicidal, and anti-cancer. On the other hand, hydrazonoyl halides are interesting synthons for valuable bioactive heterocyclic compounds. The reaction of hydrazonoyl halides with various types of substrates gave a huge number of different heterocyclic systems. In this review, we collected all reactions of hydrazonoyl halides with different moieties and classified them as aryl diazo of monoheterocycles, aryldiazo of 5,5-bis-heterocycles, aryldiazo of 5,6-bis-heterocycles, aryldiazo of 6,6-bis-heterocycles, aryldiazo of 5,5,6-tri-heterocycles, aryldiazo of 5,6,6-tri-heterocycles, aryldiazo of 6,6,6-tri-heterocycles, hetero annulation of bisheterocycles, hetero annulation of tri-heterocycles, hetero-annulation of tetra-heterocycles, synthesis of spiro-heterocycles, heterocyclic ring transformations, and 1,3-dipolar cycloaddition reactions catalyzed by transition metals using hydrazonoyl halides as substrates.Most reaction types have been successfully applied and used in the production of biologically active compounds. The aim of the present survey is to consider in the reader the opportunity interactions and biological activities of hydrazonoyl halides. The information of several artificial paths and varied physics-chemical factors of such heterocycles made a special consideration of chemists in different fields to yield a combinatorial library and carry out thorough efforts in the search for hydrazonoyl halides.

Effect of Flame Retardant R134a on the Flammability Characteristics of R1234yf

The potential alternative 2,3,3,3-tetrafluoropropene (R1234yf) has excellent environmental property but carries a risk of combustion. Therefore, 1,1,1,2-tetrafluoroethane (R134a) was chosen as the matching flame retardant. In this research, the oxidation process of R134a/R1234yf was studied by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). the oxidation products were identified for the first time, which included CO, CO2, H2O, C2H2, CH2F2 and CH2O. Then, a new kinetic model for the inhibition of R134a on R1234yf combustion was built, which well reproduced the experimental results. The inhibitory effect of R134a on the flammability of R1234yf was evidenced from the microscopic (the molar distributions of typical species and reactions) and macroscopic (adiabatic combustion temperature and laminar burning velocity) properties between pure R1234yf and R134a/R1234yf mixture. The comparative Rates of Production (ROP) analysis for key species (H2O, CO2, C2H2 and CH2F2) and radicals (H, O, OH and F), alongside sensitivity analysis were performed, which elucidated the underlying microscopic mechanism in the flame retarding process. The results also showed that the laminar burning velocity and adiabatic temperature of pure R1234yf were larger than R134a/R1234yf mixture. This paper can provide a new research idea for the safe application of environmentally friendly refrigerants.

Unveiling the optical and molecular characteristics of aging microplastics derived dissolved organic matter transformed by UV/chlor(am)ine oxidation and its potential for disinfection byproducts formation

The investigations into the existence and behavior of microplastics (MPs) in water environment were widely conducted, while the characteristics of dissolved organic matter derived from MPs (MPs-DOM) during advanced oxidation have garnered comparatively little attention. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was employed along with multiple statistical analyses to gain a deeper understanding of the conversion of MPs-DOM in UV/chlor(am)ine advanced oxidation processes (AOPs). The diverse treatments exhibited varying degrees of augmentation in both aging and fragmentation of MPs with the order of UV/Cl2 > UV > UV/NH2Cl. The fragmentation degree of MPs upon two UV-based AOPs (UV-AOPs) was dependent on their monomer chemical structure. The highest TOC values of three MPs-DOM were observed after UV/Cl2 AOP and the lowest after UV/NH2Cl AOP. Polyvinyl chloride (PVC) displayed a greater release of MPs-DOM under varying leaching conditions. UV/Cl₂ AOP favored the reaction with saturated MPs-DOM, while UV/NH₂Cl AOP reduced unsaturated MPs-DOM, alleviating disinfection byproducts (DBPs) formation after chlorination. The precursors generated by UV/Cl₂ AOP owned lower H/C, higher modified aromatic index (AImod), and lower molecular weight (MW) products after chlorination. PVC-DOM with fewer CH₂ groups was more reactive. -H₂O, +O and -CH₂ reactions dominated in PVC-DOM (CHO compounds), while -2H, +O, -CH₂ did in PVC-DOM (CHON compounds). The dominant chlorine addition/substitution reactions occurred in PVC-DOM treated by UV/Cl₂ AOP, identifying 195 Cl-DBPs with 220 precursor-product pairs. Mass difference analyses showed that +2H and +O reactions were the most frequent of the 24 reaction types. Environmental ImplicationMicroplastics derived dissolved organic matters (MPs-DOM) transformed into disinfection byproducts (DBPs) under advanced oxidation processes (AOPs), heightening environmental risks. In this study, Fourier transform ion cyclotron resonance mass spectrometry was employed to gain a deeper understanding of MPs-DOM conversion in UV/chlor(am)ine AOPs. MPs fragmentation and fluorescent components varied with monomer chemistry and polymers. UV/Cl₂ AOP reacted with saturated MPs-DOM. UV/NH₂Cl AOP reduced unsaturated MPs-DOM, alleviating DBPs formation. DBPs precursors generated by UV/Cl₂ AOP owned higher modified aromatic index, lower H/C and molecular weight. Unveiling the MPs-DOM transformation during AOPs can mitigate the negative environmental impacts of MPs and their derivatives.

Stereoselective chemical N-glycoconjugation of amines via CO2 incorporation

Chemical N-glycoconjugation can provide a unique way to tailor the properties of the ubiquitous amines for further expending their diverse functions and applications. Nevertheless, effective methodology for glycoconjugation of amines remains largely underdeveloped. Inspired by a biotransformation pathway of amine-containing drugs in vivo, we have developed an effective protocol that enables one-step chemical N-glycoconjugation of amines in high stereoselectivity under mild conditions. This protocol involves conversion of the amine moiety into the corresponding carbamate anion under CO2 atmosphere and a subsequent SN2 type reaction with glycosyl halides. This work provides an example of using CO2 as the coupling unit in chemical glycoconjugation reactions. A case study on the resulting N-glycoconjugates of Crizotinib, an anticancer drug, demonstrates a quick cleavage of the glucosyl carbamate linkage, testifying that this N-glyconjugation method could serve as a general approach to procure novel prodrugs.

Unveiling the role of aniline as a Brønsted base in Rh-catalyzed C−H alkylation: Computational insights into amino-assisted outer-sphere CMD

C−H bond cleavage is a key step for the formation of new C−Rh bond in Rh-catalyzed alkylation of aniline derivatives. Due to the inherent basicity of aniline, there is ongoing debate regarding its ability to act as a Brønsted base to assist C−H bond cleavage in these type reactions. In this report, we present computational evidence supporting an amino-assisted outer-sphere concerted metalation-deprotonation (CMD) mechanism. Here, the aniline acts as a Brønsted base to facilitate C−H bond cleavage without any direct interaction between the Rh and the aniline. This amino-assisted outer-sphere CMD pathway is found to be lower in energy compared with the inner-sphere CMD and other base-assisted C−H bond cleavage pathways, providing new insights into the mechanism of Rh-catalyzed C−H functionalization of aniline derivatives. Geometric analysis was conducted to elucidate details of the C−H bond cleavage process. This mechanistic study of C−H bond cleavage in Rh-catalyzed oxidative C−H alkylation of aniline derivatives with allyl alcohols is an important case study of the involvement of amino-assisted outer-sphere CMD in Rh catalysis. We anticipate that the novel amino-assisted outer-sphere CMD mode may extend to other C−H bond functionalization processes and explain the unique effectiveness of aniline in many instances.

Systematic, computational discovery of multicomponent and one-pot reactions

Discovery of new types of reactions is essential to organic chemistry because it expands the scope of accessible molecular scaffolds and can enable more economical syntheses of existing structures. In this context, the so-called multicomponent reactions, MCRs, are of particular interest because they can build complex scaffolds from multiple starting materials in just one step, without purification of intermediates. However, for over a century of active research, MCRs have been discovered rather than designed, and their number remains limited to only several hundred. This work demonstrates that computers taught the essential knowledge of reaction mechanisms and rules of physical-organic chemistry can design – completely autonomously and in large numbers – mechanistically distinct MCRs. Moreover, when supplemented by models to approximate kinetic rates, the algorithm can predict reaction yields and identify reactions that have potential for organocatalysis. These predictions are validated by experiments spanning different modes of reactivity and diverse product scaffolds.

Structure of dimerized assimilatory NADPH-dependent sulfite reductase reveals the minimal interface for diflavin reductase binding.

Sulfur is one of the essential building blocks of life. Sulfur exists in numerous redox states but only one can be incorporated into biomass - S 2- (sulfide). In Escherichia coli , a protein enzyme called sulfite reductase reduces sulfite by six electrons to make sulfide. Typical electron transfer reactions move one or two electrons at a time, so this chemistry is unique. E. coli SiR is a two-protein complex composed of a diflavin reductase flavoprotein and an iron metalloenzyme hemoprotein. Until now, the molecular interactions that govern subunit interactions remained a mystery because the extreme flexibility of the flavoprotein subunit, which has challenged X-ray or cryo-EM analysis for over 30 years. In overcoming these challenges, we used a combination of rapid plunging with a high critical-micelle-concentration lipid alongside a biochemically minimized complex to determine the 2.78 Å-resolution cryo-EM structure of a dimer between the flavoprotein and hemoprotein subunits.

Molecular Oxygen (O2) Artifacts in Tandem Mass Spectra.

Peak annotation plays an important role in mass spectral evaluation of the NIST 2023 tandem mass spectral library. While most fragment ions are formed by neutral losses, there are peaks that represent adduct ions from these fragments. Previously, we have reported two main types of addition reactions in the collision cell, namely addition of H2O and N2. Here we report a different reaction in the collision cell, with addition of O2 leading to a small peak that could only be assigned to a peroxyl radical ion. For example, some protonated iodoaromatics lose an iodine atom to form a radical cation [M+H-I]+•, which reacts with O2 to generate a peroxyl radical ion [M+H-I+O2]+•. Higher concentrations of O2 result in higher peroxyl radical peaks, which become dominant while the precursor ions are consumed, as examined by five compounds under different concentrations of O2. The correlation of the peroxyl radical peak intensities to the concentration of O2 provides a tool to estimate trace amounts of O2 within the instrument. In the NIST 2023 tandem mass spectral library, the peaks for [M+H-X+O2]+· are most abundant in numbers and in intensity for X = NO2 or I, are much less abundant for X = Br, and are rare for X = Cl. Other leaving groups in this library are SO3H, SO2NH2, CSNH2, CO2C6F5, SO2CH3, and COCH3. The O2 addition reaction is also observed with negative ions in this library. While adducts of H2O and N2 often constitute major peaks, the peaks of the peroxyl radicals under standard conditions are mostly very small and may be mistaken for noise, but their correct annotation improves the quality of the spectra and is important when comparing spectra from different instruments or conditions.

Rapid Exploration of Chemical Space by High-Throughput Desorption Electrospray Ionization Mass Spectrometry.

This study leverages accelerated reactions at the solution/air interface of microdroplets generated by desorption electrospray ionization (DESI) to explore the chemical space. DESI is utilized to synthesize drug analogs at an overall rate of 1 reaction mixture per second, working on the low-nanogram scale. Transformations of multiple drug molecules at specific functionalities (phenol, hydroxyl, amino, carbonyl, phenyl, thiophenyl, and alkenyl) are achieved using electrophilic/nucleophilic, redox, C-H functionalization, and coupling reactions. These transformations occur under ambient conditions on the millisecond time scale with direct detection of products being successful in all but three of the reaction types studied. The large scope (22 bioactive compounds, >20 chemical transformations, and >300 functionalization reagents) and high speed (>3000 reactions/hour) provide access to a wide array of drug analogs that can be used for bioactivity testing. A total of ∼6800 unique reactions were examined through a data-driven workflow, and more than 3000 unique derivatives (∼44%) were identified tentatively by the m/z value and signal-to-control ratio in single-stage mass spectrometry (MS) analysis, with over 1000 being further characterized by tandem MS. The speed of the DESI-MS reaction screen provides potential advantages for emerging machine learning-based predictions of organic synthesis, and it sets the stage for future online DESI-MS bioassays and scaled-up microdroplet synthesis before formal characterization of hit compounds is sought using traditional methods of drug discovery.

Management of Fusarium Wilt of Lettuce

Abstract In recent years, Fusarium wilt, caused by Fusarium oxysporum f. sp. lactucae, has become the most important lettuce disease throughout the world. Since the pathogen is seed-transmitted, the disease spreads through infected seeds, favoured by the global commerce. We describe the biology and epidemiology of the pathogen, as well as the differentiation of four physiological races, with their distribution in different geographical areas. The reaction of the lettuce types and varieties to the pathogen are also described, as well as the diagnostic tools available for an appropriate detection of the pathogen, including the races. Like other soil-borne diseases, Fusarium wilt of lettuce is difficult to manage with a single product and/or with a single approach. At present, minimizing crop losses due to Fusarium wilt on lettuce entails the deployment of all available existing disease control tools within an integrated management programme. The first preventative strategy is the use of healthy seeds. Stock seeds should be produced in the areas associated with the lowest disease risk and subjected to standardized health analysis. Furthermore, seeds should be treated with chemical/physical or biological treatments. Among chemical tools, soil disinfestation is becoming very difficult due to the loss of registered fumigants. A careful monitoring of the race situation in the field would be useful for efficient use of genetic means of control. The seed industry is investing in the search of new varieties resistant to Fusarium wilt. Looking forward, the development of commercially acceptable cultivars of desired types of lettuce with high levels of resistance to Fusarium wilt as well as refinement of existing or development of new cultural, chemical and biofungicide tools should lead to more efficient and effective disease management. Information © The Authors 2024