Mechanism Of Addition Reaction Research Articles

An affordable, field-deployable detecting system for cyanide ion – Investigating applications in real time uses

A highly efficient system that incorporates the instantaneous visualization of the cyanide ion in water was synthesized by keeping the fluorophore system (electron donor) as a julolidine-coumarin conjugate and changing the electron acceptor unit. The probes exhibit a notable color change in normal and UV light. The probe interaction modalities are based on the ICT process. With a detection limit in the nM range, it may preferentially react with cyanide, which is less than the tolerable level of 1.9 μM. According to 1H NMR data, the probes detect cyanide ions by nucleophilic addition reaction mechanism. Furthermore, current probe successfully determines real resources, including cyanide containing cassava powder, sprouted potatoes and various water samples. Besides the test strips, an electronic Arduino device was also employed to detect the cyanide ion. As such, the developed probes exhibit outstanding practical application with respect to the cyanide ion.

Reaction mechanisms of chlorinated disinfection byproducts formed from nitrophenol compounds with different structures during chlor(am)ination and UV/post-chlor(am)ination

Nitrophenol compounds (NCs) have high formation potentials of disinfection byproducts (DBPs) in water disinfection processes, however, the reaction mechanisms of DBPs formed from different NCs are not elucidated clearly. Herein, nitrobenzene, phenol, and six representative NCs were used to explore the formation mechanisms of chlorinated DBPs (Cl-DBPs) during chlor(am)ination and UV/post-chlor(am)ination. Consequently, the coexistence of nitro and hydroxy groups in NCs facilitated the electrophilic substitution to produce intermediates of Cl-DBPs, and the different positions of nitro and hydroxy groups also induced different yields and formation mechanisms of Cl-DBPs during the chlorination and UV/post-chlorination processes. Besides, the amino, chlorine, and methyl groups significantly influenced the formation mechanisms of Cl-DBPs during the chlorination and UV/post-chlorination processes. Furthermore, the total Cl-DBPs yields from the six NCs followed a decreasing order of 2-chloro-3-nitrophenol, 3-nitrophenol, 2-methyl-3-nitrophenol, 2-amino-4-nitrophenol, 2-nitrophenol, and 4-nitrophenol during chlorination and UV/post-chlorination. However, the total Cl-DBPs yields from the six NCs during chloramination and UV/post-chloramination followed a quite different order, which might be caused by additional reaction mechanisms, e.g., nucleophilic substitution or addition might occur to NCs in the presence of monochloramine (NH2Cl). This work can offer deep insights into the reaction mechanisms of Cl-DBPs from NCs during the chlor(am)ination and UV/post-chlor(am)ination processes.

Bio-Coated Graphitic Carbon Nitrides for Enhanced Nitrobenzene Degradation: Roles of Extracellular Electron Transfer

Graphitic carbon nitrides (g-C3N4) and microorganisms could collaboratively enhance photocatalytic properties or facilitate environmental depollution through coupled photocatalytic and biological reactions, which prevented the destruction of photocatalytic stresses to ecological systems and resulted in a sustainable technology for water remediation in rivers and lakes. However, the roles of bio-substances as well as electronic interactions between inorganic and organic systems were still unclear. Herein, g-C3N4, nitrogen-deficient g-C3N4 (ND-g-C3N4), and fluorinated g-C3N4 (F-g-C3N4) were coated with representative bacteria, i.e., Escherichia coli MG 1655, and characterized using integrated spectroscopic techniques. Photocatalytic activities were then evaluated through nitrobenzene degradation performance in an aqueous solution under visible light illumination. Nano-photocatalysts were observed to be adsorbed onto bio-aggregates, and surface hydrophilicity was convinced to be determined in the toxicity of photocatalysts in dark environments. Layered structures of ND-g-C3N4 and F-g-C3N4 were revealed in XRD spectra, and surface coverage of the Luria–Bertani medium was eliminated during E. coli cultivation. Hetero-junctions between photocatalysts and bio-substances were indicated in XPS results. Red-shifts for g-C3N4 and F-g-C3N4 materials as well as a slight blue-shift for ND-g-C3N4 were demonstrated in UV-vis spectra, which might be attributed to the destruction of nitrogen defects on ND-g-C3N4. Owing to the attached bio-substances, nitrobenzene removal could reach twice that with pristine photocatalysts, and ROS quantitative analysis confirmed that hydroxyl radicals were the determined reactive species degrading nitrobenzene in the water solution. The observation of more OH species generation indicated that extracellular electron transfer of E. coli reduced electron–hole recombination and provided reduction sites during photocatalytic degradation of nitrobenzene. This work proved additional electron-transfer paths and reaction mechanisms in hybridized photocatalytic and biological processes, which indicated that bio-activities could be a great promoter of material modification and the incorporation between inorganic and organic systems successfully showed an eco-friendly and sustainable pathway to utilize photocatalysts in natural water.

Amorphous nickel fluorosulfate cathode achieving a high-capacity by an additional electrochemical reaction mechanism

Although lithium-ion cathode materials with crystal structure are extensively applied, many intrinsic problems are inevitable, such as the low capacity ascribed to the need to sacrifice a large amount of active Li to maintain the crystal structure, and the spontaneous irreversible phase transition of the crystal during the cycles, which will lead to the deterioration or even inactivation of the crystal structure, resulting in poor cyclic stability of the crystal material. Herein, an amorphous nickel fluorosulfate cathode material (a-LNSF) is fabricated by a simple mechanical ball grinding method and compared with the electrochemical properties of LNSF with crystal structure. Comparing with LNSF, a-LNSF exhibits a high discharge specific capacity of 238.5 mAh/g at a current density of 0.1 C, and the specific capacity is still 118.3 mAh/g under a high current density of 10 C. Moreover, the capacity retention ratio is 85.7 % after 300 cycles at the current density of 1 C. a-LNSF achieves satisfactory electrochemical properties attributed to its inherently advantages of the amorphous structure. Theoretical calculations coupled with experiments to further explore the reason of superior electrochemical properties of a-LNSF, and an additional electrochemical reaction mechanism for capacity accumulation were discovered. Interestingly, the directional reversible migration of F-ions (stemming from the a-LNSF) between bulk material and carbon nanotubes is accompanied by the process of charge and discharge, the C-F ionic bonds with excellent reversibility and electronic conductivity are formed to improve the comprehensive electrochemical properties of a-LNSF during the charge/discharge processes.

Propiolic Acids in the Synthesis of N-heterocycles

: This review discussed the synthetic applications of propiolic acids in the preparation of diverse N-heterocycles. 3~9-membered rings like azirines, β-lactams, oxazolidin-2-ones, 2-oxindoles, indoles, isoindolin-1-ones, imidazo[1,2-a]pyridines, triazoles, 2-pyridones, 2-quinolones, 1,4- benzothiazines, thiazinones, spiroindolines, etc. could be constructed via radical addition, fourcomponent Ugi reactions, 1,3-dipolar cycloadditions, or Diels-Alder reaction mechanism. We hope this review will promote future research in this area Introduction;: Synthesis of azirines; Synthesis of lactams; Construction of five-membered rings; Construction of six-membered rings; Double cyclization for N-heterocycles; Construction of 7~9- membered rings; Conclusion.

An acetylpyrene-based fluorescent probe for selective detection of cysteine in vitro and in lipid droplets

The development of organelle-targeted probes that enable specific recognition and detection Cysteine (Cys) may provide an effective way to explore physiological processes and pathological mechanisms associated with the related diseases. In this work, an acetylpyrene-based fluorescent probe CP-1 was designed and synthesized for detecting Cys in vitro and in vivo. The probe exhibited a noticeable fluorescence blue shift upon the addition of Cys under UV light, attributed to the mechanism of the nucleophilic addition reaction. The response mechanism for Cys was studied by time-dependent density functional theory (TD-DFT) calculations and mass spectra (MS). CP-1 can not only specifically recognize Cys in the presence of other amino acids and biothiols, but also exhibit the property of targeting lipid droplets (LDs). Due to the good cell biocompatibility, CP-1 has been successfully employed for real-time tracking Cys in LDs of living cells. The ability to target LDs and the favorable biocompatibility make the probe valuable for investigating Cys-related diseases in living cell systems.

Trivinylphosphine Oxide: Synthesis, Characterization, and Polymerization Reactivity Investigated Using Single-Crystal Analysis and Density Functional Theory.

Organophosphorus chemicals are versatile and important in industry. Trivinylphosphine oxide (TVPO), for example, exhibited a promising precursor as a flame-retardant additive for industrial applications. Density functional theory (DFT) simulations were used to explore the kinetic and thermodynamic chemical processes underlying the nucleophilic addition reactions of TVPO in order to better understand their polymerization mechanisms. An experimental X-ray single-crystal study of TVPO supported this work's theory based on its computed findings. TVPO was prepared using POCl3 and VMB in a temperature-dependent reaction. TVPO, the thermodynamically favourable product, is preferentially produced at low temperatures. The endothermic anionic addition polymerization reaction between TVPO and VMB begins when the reaction temperature rises. An implicit solvation model simulated TVPO and piperazine reactions in water, whereas a hybrid model modelled VMB interactions in tetrahydrofuran. The simulations showed a pseudo-Michael addition reaction mechanism with a four-membered ring transition state. The Michael addition reaction is analogous to this process.

Computational Investigations of Reaction Mechanisms and Transformation Products of Olefins with Hypochlorous Acid.

Hypochlorous acid (HOCl) as the main component in chlorination and also as the innate immune factor relevant to immune defense has attracted considerable attention. Electrophilic addition reaction of olefins with HOCl, one of the most important prototype of chemical reactions, has been intensively studied for a long time; however, it has not been fully understood yet. In this study, addition reaction mechanisms and transformation products of model olefins with HOCl were systematically investigated by the density functional theory method. The results indicate that the traditionally believed stepwise mechanism with a chloronium-ion intermediate is only suitable for olefins substituted with electron-donating groups (EDGs) and weak electron-withdrawing groups (EWGs) but it is a carbon-cation intermediate that is favorable for EDGs featuring p-π or π-π conjugation with the C═C moiety. Moreover, olefins substituted with moderate or/and strong EWGs prefer the concerted and nucleophilic addition mechanisms, respectively. Epoxide and truncated aldehyde as the main transformation products can be generated from chlorohydrin through a series of reactions involving hypochlorite; however, their generation is kinetically not as feasible as the formation of chlorohydrin. The reactivity of three chlorinating agents (HOCl, Cl2O, and Cl2) and the case study of chlorination and degradation of cinnamic acid were also explored. Additionally, APT charge on the double-bond moiety in olefin and energy gap (ΔE) between the highest occupied molecular orbital (HOMO) energy of olefin and the lowest unoccupied molecular orbital (LUMO) energy of HOCl were found to be good parameters to distinguish the regioselectivity of chlorohydrin and reactivity of olefin, respectively. The findings of this work are helpful in further understanding the chlorination reactions of unsaturated compounds and identifying complicated transformation products.

A dual-response fluorescent probe for SO2 and viscosity in lysosomes

As a signal molecule, SO2 plays an important role in the process of cell metabolism. The abnormal level of sulfur dioxide will induce many diseases of human body. Viscosity is an important index of lysosome. Abnormal lysosome viscosity can also lead to many diseases. Therefore, we have developed a new fluorescence probe PAPD for simultaneous imaging of sulfur dioxide derivatives and lysosomal viscosity. The probe realizes rapid detection of HSO3− based on Michael addition reaction mechanism. At the same time, with the increase of viscosity, intramolecular rotation is inhibited, thus the probe shows sensitive fluorescence enhancement. In addition, the results of the co-localization experiments show that PAPD has good lysosomal targeting ability. Further studies show that PAPD can be used as a dual-responsive fluorescence probe for SO2 and viscosity in lysosomes.

Investigation of the Asymmetric Addition Reactions Induced by Pentacoordinated Hydrospirophosphorane Substrate.

Pentacoordinated bisaminoacyl hydrospirophosphoranes were first found to induce the asymmetric addition reactions as a novel chiral organic framework. Asymmetric addition reactions of bisaminoacyl hydrospirophosphoranes with aromatic aldehyde and in situ generated imine were investigated, and the corresponding α-hydroxyspirophosphonates and α-amino spirophosphonates were obtained. The addition reaction of hydrospirophosphoranes with ΔP configuration showed better stereoselectivity than that with ΛP configuration, not only for the addition reaction to aromatic aldehyde but also to in situ generated imine. Furthermore, the stereochemical mechanisms of asymmetric addition reactions induced by pentacoordinated hydrospirophosphorane were proposed by 31P NMR tracing experiment and X-ray diffraction analysis.

A mechanistic study of thiol addition to N-acryloylpiperidine.

Nucleophilic cysteine (Cys) residues are present in many enzyme active sites and represent the target of many different irreversible enzyme inhibitors. Given its fine balance between aqueous stability and thiolate reactivity, the acrylamide group is a particularly popular warhead pharmacophore among inhibitors designed for biological and therapeutic application. The acrylamide group is well known to undergo thiol addition, but the precise mechanism of this addition reaction has not been studied in as much detail. In this work we have focussed on the reaction of N-acryloylpiperidine (AcrPip), which represents a motif found in many targeted covalent inhibitor drugs. Using a precise HPLC-based assay, we measured the second order rate constants for the reaction of AcrPip with a panel of thiols possessing different pKa values. This allowed construction of a Brønsted-type plot that reveals the relative insensitivity of the reaction to the nucleophilicity of the thiolate. By studying temperature effects, we were able to construct an Eyring plot from which the enthalpy and entropy of activation were calculated. Ionic strength and solvent kinetic isotope effects were also studied, informing on charge dispersal and proton transfer in the transition state. DFT calculations were also performed, providing information on the potential structure of the activated complex. Taken together, these data strongly support one cohesive addition mechanism that is the microscopic reverse of the E1cb elimination, and highly relevant to the intrinsic thiol selectivity of AcrPip inhibitors and their subsequent design.

Mercapto-pyrimidines are reversible covalent inhibitors of the papain-like protease (PLpro) and inhibit SARS-CoV-2 (SCoV-2) replication.

The papain-like protease (PLpro) plays a critical role in SARS-CoV-2 (SCoV-2) pathogenesis and is essential for viral replication and for allowing the virus to evade the host immune response. Inhibitors of PLpro have great therapeutic potential, however, developing them has been challenging due to PLpro's restricted substrate binding pocket. In this report, we screened a 115 000-compound library for PLpro inhibitors and identified a new pharmacophore, based on a mercapto-pyrimidine fragment that is a reversible covalent inhibitor (RCI) of PLpro and inhibits viral replication in cells. Compound 5 had an IC50 of 5.1 μM for PLpro inhibition and hit optimization yielded a derivative with increased potency (IC50 0.85 μM, 6-fold higher). Activity based profiling of compound 5 demonstrated that it reacts with PLpro cysteines. We show here that compound 5 represents a new class of RCIs, which undergo an addition elimination reaction with cysteines in their target proteins. We further show that their reversibility is catalyzed by exogenous thiols and is dependent on the size of the incoming thiol. In contrast, traditional RCIs are all based upon the Michael addition reaction mechanism and their reversibility is base-catalyzed. We identify a new class of RCIs that introduces a more reactive warhead with a pronounced selectivity profile based on thiol ligand size. This could allow the expansion of RCI modality use towards a larger group of proteins important for human disease.

Additional reaction mechanisms to statistical α-emission and the related optical-potential validation

The major role of consistent parameter sets within analysis of neutron-induced α-particle emission, for the assessment of a possible difference between the optical model potentials (OMPs), which describe either alpha-particle elastic scattering and induced reactions or alpha-emission from excited compound nuclei, is shown. They are involved at variance with use of either empirical rescaling factors of the γ and/or neutron widths or even combinations of all options of a computer code for main input parameters. Suitable description of all competitive reaction channels, confirmed by a careful uncertainty analysis in order to avoid parameter ambiguities and/or error compensation, supports further consideration of additional direct processes.

Theoretical Study of Atom-Transfer Radical Addition Reactions between Perfluoroalkyl Iodides and Styrene Using a Copper Photoredox Catalyst.

The reaction mechanism of atom-transfer radical addition (ATRA) reactions of perfluoroalkyl iodides with styrene using a Cu(I) photoredox catalyst was analyzed using density functional theory calculations. From among four previously mentioned mechanisms, the ligand-transfer mechanism (ligand abstraction by the radical intermediate) was shown to be most plausible. It was also suggested that the ATRA product would also be reduced by the photoexcited Cu(I) complex.

Resolving the Mechanistic Complexity in Triarylborane-Induced Conjugate Additions

Previous studies have shown that the catalytically active species in the Lewis acid-catalyzed addition reactions of allyl silanes or silyl enol ethers to carbonyl compounds or Michael acceptors are often silylium-carbonyl adducts rather than the adducts of the carbonyl group with the Lewis acid used for the induction of the reaction. Indirect evidence for such catalyst variations has so far been derived from double-label crossover experiments and comparisons of absolute reaction rates. We have now performed a detailed investigation on the kinetics and mechanism of the triarylborane-initiated conjugate addition reactions of allylsilanes and silyl enol ethers to α,β-unsaturated carbonyl compounds. NMR spectroscopic monitoring of such reactions gave rise to sigmoidal kinetic profiles, allowing us to directly follow the change of the catalytically active Lewis acid from triarylboranes in the induction period to silylium ions during the main part of the reaction. Crossover experiments and the isolation of four- and five-membered cyclic intramolecular trapping products provided further insight into the mechanism. DFT calculations of various mechanistic variants and kinetic modeling elucidated the operation of a complex reaction network, which rationalizes the experimental observations.

A coumarin/cyanoacetamide-derived lysosome-targeting probe for detecting bisulfite and viscosity changes in living cells and zebrafish

A coumarin/cyanoacetamide-based probe was produced by a simple condensation reaction. The probe exhibits high selectivity towards bisulfite (HSO3−) and viscosity changes based on either fluorescence or UV–Vis spectra in almost pure aqueous media. The addition of HSO3− induced a significant blue shift in the emission maximum of the free probe (from 575 nm to 485 nm) with a short response time (5 min), a broad function pH range (3.0–11.0), and a low detection limit (74 nM), via the recognition mechanism of bisulfite-involved Michael addition reaction. In parallel, the fluorescence intensity at 575 nm of the probe increased significantly along the increasing viscosity of the test media owing to the prohibited rotation of CC bridged rotors in probe 1. Notably, the probe could monitor the level of lysosomal HSO3− and viscosity changes in HeLa cells and zebrafish.

Carbon‐Supported Au Catalyst in Acetylene Hydrochlorination: Enhancing Catalytic Performance by Complexation of Dicarbonyl Ligands

AbstractCarbon‐supported Au (Au/AC) has been proven to be one of the most promising catalysts in the field of acetylene hydrochlorination. However, the catalytic performance of conventional Au/AC catalyst is usually limited due to the unsatisfactory dispersion of active Au cation on the surface of the support, carbon deposition, and inevitable reduction to inactive Au nanoparticles. Herein, Au catalysts with highly dispersed Au cation were developed using the complexation of dicarbonyl ligand N‐chlorosuccinimide (NCS) and N‐methylsuccinimide (NMS). The obtained Au−NMS/AC and Au−NCS/AC catalysts with 0.1 wt.% Au loading possessed acetylene conversion of 98 % and 88 % at 180 °C and GHSV (C2H2) of 160 h−1, which were clearly better than that of pristine Au/AC. The characterization results showed that coordination between Au cation and ligands enhanced the dispersion of Au species, suppressed the reduction of Au cation, and reduced the formation of carbon deposits. Density functional theory (DFT) calculations suggest that Au−NMS/AC and Au−NCS/AC catalysts follow a HCl‐preferred concerted addition reaction mechanism with lower reaction energy barrier. This favors the high activity and nuclearity stability of the Au center. This study provides great potential for the use of dicarbonyl ligands on Au‐based catalysts in acetylene hydrochlorination.

Polydopamine and Mercapto Functionalized 3D Carbon Nano-Material Hybrids Synergistically Modifying Aramid Fibers for Adhesion Improvement.

In order to solve the problem of poor interfacial adhesion between aramid fibers and a rubber matrix, an efficient and mild modification method was proposed via polydopamine and mercapto functionalized graphene oxide (GO) and carbon nanotube (CNTs) hybrids synergistically modifying aramid fibers. GO and CNTs were firstly stacked and assembled into unique 3D GO-CNTs hybrids through π-π conjugation. Then, the mercapto functionalization of the assembled 3D GO-CNTs hybrids was realized via the dehydration condensation reaction between the hydroxyls of GO and the silanol groups of coupling agent. Finally, the mercapto functionalized 3D GO-CNTs hybrids were grafted onto the aramid fibers, which were pre-modified by polydopamine through the Michael addition reaction mechanism. The surface morphology and chemical structures of GO-CNTs hybrids and fibers and the interfacial adhesion strength between fibers and rubber matrix were investigated. The results showed that the modification method had brought about great changes in the surface structure of fibers but not generated any damage traces. More importantly, this modification method could improve the interfacial strength by 110.95%, and the reason was not only the reactivity of functional groups but also that the 3D GO-CNTs hybrids with excellent mechanical properties could effectively share interfacial stress. The method proposed in this paper was universal and had the potential to be applied to other high-performance fiber-reinforced composites.

Studies of the 2α and 3α channels of the 12C+12C reaction in the range of E c.m.=8.9 MeV to 21 MeV using the active target Time Projection Chamber* *Supported in part by the Strategic Priority Research Program of Chinese Academy of Sciences (XDB34020200), the National Key Research and Development program (MOST 2016YFA0400501) from the Ministry of Science and Technology of

The 12C+12C fusion reaction was studied in the range of E c.m.=8.9 to 21 MeV using the active-target Time Projection Chamber. With full information on all tracks of the reaction products, cross sections of the 12C(12C,8Be)16Og.s. channel and the 12C(12C,3α)12C channel could be measured down to the level of a few milibarns. The 12C(12C,8Be)16Og.s. reaction channel was determined to be 10 mb at E c.m.=11.1 MeV, supporting the direct α transfer reaction mechanism. The 12C(12C,3α)12C reaction channel was studied for the first time using an exclusive measurement. Our result does not confirm the anomaly behavior reported in the previous inclusive measurement by Kolata et al. [Phys. Rev. C 21, 579 (1980)]. Our comparisons with statistical model calculations suggest that the 3α channel is dominated by the fusion evaporation process at E c.m. > 19 MeV. The additional contribution of the 3α channel increases the fusion reaction cross section by 10% at energies above 20 MeV. We also find that an additional reaction mechanism is needed to explain the measured cross section at E c.m. < 15 MeV at which point the statistical model prediction vanishes.

Studying on the Addition Reaction Mechanism of Ethylene and Butadiene based on Density Functional Theory

Only one-step reaction has been identified for the addition reaction mechanism of ethylene and butadiene based on the first principles calculations. The reactant, product, and transition state (TS) are determined by optimization calculation and confirmed by frequency analysis. The intrinsic reaction coordinate is also calculated to validate the reaction process. Result shows that the whole reaction is an exothermic reaction. The charge distribution is used to understand the novel reaction. In this study, the activation energy of the addition reaction of ethylene and butadiene is 0.83eV, and the heat release of the whole reaction is 2.01eV. The molecular structure, charge distribution and energy of butadiene and ethylene are investigated at the molecular level. The calculated activation energy is helpful for understanding the cyclic addition reaction of butadiene and ethylene, providing theoretical guidance for experiments and deepening people's understanding of this reaction.