Dissociation Reactions Research Articles

Theoretical study on the effect of oxidation states of phosphorus flame retardants on their mode of action

Polymers are ubiquitous and find applications in various facets of daily life and industrial production. However, the fire incidents induced by polymers jeopardize the safety of human life and property. Improving the fire resistance of polymeric materials through halogen-free flame retardants has become a prominent direction guided by the regulatory framework. In this paper, the decomposition pathways and mechanisms of five phosphorus-containing flame retardants, PPh3, DPPO, PDPP, TPPO and TPP, were investigated. The reaction pathways primarily encompassed the generation of PO, PO2, PO3, PO4, phenyl, and phenoxy radicals. Through a comprehensive analysis of the dissociation energies of P-C, P-O, and CO bonds under diverse chemical environments, phenoxy radicals was the principal decomposition products, with the cleavage of P-O bonds being the predominant choice. Increasing phosphorus oxidation states favors the accumulation of a carbon layer, tending to retard flame propagation through condensed-phase mechanisms. Phosphorus oxidation states primarily facilitated secondary dissociation reactions. The presence of oxygen favored the cleavage of P-C bonds, offering diverse flame retardant mechanisms that concurrently mitigated flame spread. This work provided an in-depth exploration of the flame retardant mechanisms of phosphorus-containing agents and summarized the impact of phosphorus oxidation states on flame retardants.

Rational modulation of electronic structure in PtAuCuNi alloys boosts efficient electrocatalytic ethanol oxidation assisted with energy-saving hydrogen evolution

Compared to conventional electrocatalytic water splitting, electrocatalytic ethanol oxidation reaction (EOR) along with hydrogen production is considered a more energy-efficient strategy. Herein, we prepared a type of novel quaternary alloy catalyst (PtAuCuNi@NF) that exhibits excellent activity for EOR (0.215 V at 10 mA cm−2) and hydrogen evolution reaction (HER) (7 mV at 10 mA cm−2). Experimental results demonstrated that both Cu and Ni modulated the electronic environment around Pt and Au. The electron-rich active center facilitates the rapid adsorption and dissociation of reactants and intermediates for both EOR and HER. Impressively, in the ethanol-assisted overall water splitting (E-OWS), a current density of 10 mA cm−2 was achieved at 0.28 V. Moreover, an advanced acid-base self-powered system (A-Bsps) that can achieve a self-powered voltage of 0.59 V was assembled. Accordingly, the self-driven hydrogen production with zero external power supply was realized by integrating A-Bsps with the E-OWS equipment. The interesting results can provide a feasible strategy for designing and developing advanced nanoalloy-based materials for clean energy integration and use in various fields.

A DFT investigation of hydrazine nitrate dissociation mechanism on MoN(0 0 1)

Hydrazine nitrate (HN) is an important additive for hydrazine-based monopropellant. In this work, density functional theory (DFT) was adopted to calculate the decomposition process of HN components on MoN (001) catalyst surface. Firstly, two stable adsorption configurations of hydrazine nitrate were identified and determined the catalytic decomposition pathway of the thermodynamically favorable configuration. Pathway analysis revealed that the nitric acid group preferentially decomposes in all pathways. Moreover, due to the high activation and desorption energies, H2O molecules are more likely to be generated in the gas phase rather than preferentially adsorbed on the surface. By calculating the activation energies of each elementary reaction, it can be concluded that the cleavage of the NO bond in NO3– with the barrier energy of 0.32 eV plays a decisive role in the decomposition of the HN molecule.

Understanding atom probe’s analytical performance for iron oxides using correlation histograms and ab initio calculations

Field evaporation from ionic or covalently bonded materials often leads to the emission of molecular ions. The metastability of these molecular ions, particularly under the influence of the intense electrostatic field (1010Vm−1), makes them prone to dissociation with or without an exchange of energy amongst them. These processes can affect the analytical performance of atom probe tomography (APT). For instance, neutral molecules formed through dissociation may not be detected at all or with a time of flight no longer related to their mass, causing their loss from the analysis. Here, we evaluated the changes in the measured composition of FeO, Fe2O3 and Fe3O4 across a wide range of analysis conditions. Possible dissociation reactions are predicted by density-functional theory calculations considering the spin states of the molecules. The energetically favoured reactions are traced on to the multi-hit ion correlation histograms, to confirm their existence within experiments, using an automated Python-based routine. The detected reactions are carefully analyzed to reflect upon the influence of these neutrals from dissociation reactions on the performance of APT for analysing iron oxides.

Construction of In2O3@CN S-type heterojunctions with defect engineering for highly efficient photocatalytic degrade atrazine: Efficacy and mechanism evaluation

Developing exceptional photocatalysts with a high ability for photocarrier dissociation and photoredox reactions is crucial for effectively eliminate water pollutants, yet it remains a significant challenge. In this study, a S-type heterojunction with N defect, 2In2O3@CN, is constructed by incorporating In2O3 nanoparticles onto g-C3N4 nanosheet. The S-type charge transfer mode markedly promotes the space detachment of high-energy electron/hole and preservation on 2In2O3@CN, effectively suppressing the photocorrosion of In2O3. The optimized 2In2O3@CN heterojunction demonstrates superior performance. In visible light-driven photocatalytic degradation of atrazine, the efficiency reaches an impressive 81.5%. The pseudo-first-order kinetics are 12.7 times higher than those of pure CN, while maintaining excellent stability and reusability. Calculations and liquid mass measurements have revealed the primary active substances, intermediates, and photodegradation pathways in the photocatalytic process. This study not only offers a potential photocatalyst for safeguarding aquatic environments but also encourages the exploration of novel and potent CN-based S-type photocatalysts for environmental protection.

Controlling Phase in Colloidal Synthesis.

A fundamental precept of chemistry is that properties are manifestations of the elements present and their arrangement in space. Controlling the arrangement of atoms in nanocrystals is not well understood in nanocrystal synthesis, especially in the transition metal chalcogenides and pnictides, which have rich phase spaces. This Perspective will cover some of the recent advances and current challenges. The perspective includes introductions to challenges particular to chalcogenide and pnictide chemistry, the often-convoluted roles of bond dissociation energies and mechanisms by which precursors break down, using very organized methods to map the synthetic phase space, a discussion of polytype control, and challenges in characterization, especially for solving novel structures on the nanoscale and time-resolved studies.

Interfacial strain induced crystalline-amorphous nanoarchitectures anchoring MoO42− anionic groups to alleviate self-discharge of battery-type cathodes

Battery-type cathodes that endow supercapacitors (SCs) with high energy density have severe self-discharge defect. However, the underlying origin and regulation strategy have never been reported. In this work, we proposed an advanced in-situ anionic group anchoring strategy utilizing the strain effect between external NCZ-LDH and internal NiMoO4. Combining experiments with theoretical calculation, we confirmed that the self-discharge behavior of battery-type cathodes is highly related with the dissociation reaction of H2O in fully charged state, while the defect can be significantly alleviated through the modification of MoO42− in the reconstructed strain induced crystalline-amorphous nanoarchitectures, which optimizes the adsorption and dissociation energies of H2O. As a result, the NiMoO4@NCZ-LDH electrode not only exhibits excellent capacity and durability, but also significantly increases capacity retention from 21.3 % to 79.7 % after self-discharge for 72 h and keeps in a high open circuit potential throughout. This study fills the blank of battery-type cathodes in self-discharge research and points out a promising direction for designing high performance SCs.

Photodissociation Dynamics of the Highly Stable ortho-Nitroaniline Cation.

0rtho-Nitroaniline (ONA) is a model for the insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) that shares strong hydrogen bonding character between adjacent nitro and amino groups. This work reports femtosecond time-resolved mass spectrometry (FTRMS) measurements and theoretical calculations that explain the high stability of the ONA cation compared with related nitroaromatic molecules. Ab initio calculations found that the lowest-lying electronic excited state of the ONA cation, D1, lies more than 2 eV above the ground state, and the energetic barriers to rearrangement and dissociation reactions exceed this D1 energy. These theoretical results were confirmed by FTRMS pump-probe measurements showing that (1) fragment ions represented less than 30% of the total ion yield when a 1014 W cm-2, 1300 nm, 20 fs pump pulse was used to ionize ONA; and (2) 3.1 eV (400 nm) photons were required to induce dissociation of the ONA cation. Stronger coupling between the ground D0 and excited D4 states of the ONA cation at the geometry of neutral ONA resulted in a transient enhancement of fragment ion yields at <300 fs pump-probe delay times, prior to relaxation of the ONA cation to its optimal geometry.

Problematic gaming, social withdrawal, and Escapism: The Compensatory-Dissociative Online Gaming (C-DOG) model

In this article, we critically overview existing studies on compensatory and dissociative mechanisms associated with problematic gaming, with a focus on escapism. Thus, we present a theoretical model integrating current research. In the first section, we link compensatory and dissociative processes related to gaming on a continuum that corresponds to the degree of connection/rupture between physical and virtual environments of the individual. In the second section, we discuss the strengths and limitations of existing conceptualizations and measures of escapism. We contend that escapism in gaming represents a key dimension of the compensation for difficulties in psychological needs satisfaction in the physical environment, differently from escape (avoidance) and from general immersion in video games. In the last section, we elaborate the Compensatory-Dissociative Online Gaming (C-DOG) model, which defines a set of interconnected psychological processes operationalizing the continuum between adaptive and pathological online gaming: relaxation, body-mind detachment, active escapism, escape, and dissociation. This model provides an unprecedented way to consider meaningful processes for the clinical evaluation and treatment of problematic gaming, as well as the association of problematic gaming with emerging social withdrawal conditions, such as hikikomori.

Binding of Carbon Monoxide to Hemoglobin in an Oxygen Environment: Force Field Development for Molecular Dynamics.

Carbon monoxide (CO) is a byproduct of the incomplete combustion of carbon-based fuels, such as wood, coal, gasoline, or natural gas. As incomplete combustion in a fire accident or in an engine, massively produced CO leads to a serious life threat because CO competes with oxygen (O2) binding to hemoglobin and makes people suffer from hypoxia. Although there is hyperbaric O2 therapy for patients with CO poisoning, the nanoscale mechanism of CO dissociation in the O2-rich environment is not completely understood. In this study, we construct the classical force field parameters compatible with the CHARMM for simulating the coordination interactions between hemoglobin, CO, and O2, and use the force field to reveal the impact of O2 on the binding strength between hemoglobin and CO. Density functional theory and Car-Parrinello molecular dynamics simulations are used to obtain the bond energy and equilibrium geometry, and we used machine learning enabled via a feedforward neural network model to obtain the classical force field parameters. We used steered molecular dynamics simulations with a force field to characterize the mechanical strength of the hemoglobin-CO bond before rupture under different simulated O2-rich environments. The results show that as O2 approaches the Fe2+ of heme at a distance smaller than ∼2.8 Å, the coordination bond between CO and Fe2+ is reduced to 50% bond strength in terms of the peak force observed in the rupture process. This weakening effect is also shown by the free energy landscape measured by our metadynamics simulation. Our work suggests that the O2-rich environment around the hemoglobin-CO bond effectively weakens the bonding, so that designing of O2 delivery vector to the site is helpful for alleviating CO binding, which may shed light on de novo drug design for CO poisoning.

Parameterization of the IEF PCM model for calculating solvation energies in N-methylpyrrolidone solution

ABSTRACT Theoretical modelling of N-methylpyrrolidone (NMP) solutions, using a polarisable continuum model (IEFPCM), has been carried out with the aim to find the optimal value of a model parameter, a so-called scaling factor (α) for NMP, which should afford an improved modelling of various N-methylpyrrolidone solutions. Our working protocol comprised evaluations of the Gibbs free energy for the dissociation reaction of a set of 22 acids, employing the B2PLYP-D2/6–311+G**//B3LYP/6–31+G* approach, which were then used to calculate the acidity indices by considering the solvation energy at various values of α within the IEFPCM model. The optimal value of α for the N-methylpyrrolidone solvent has been found to amount to 1.40.

Strategies to improve hydrogen activation on gold catalysts.

Catalytic reactions involving molecular hydrogen are at the heart of many transformations in the chemical industry. Classically, hydrogenations are carried out on Pd, Pt, Ru or Ni catalysts. However, the use of supported Au catalysts has garnered attention in recent years owing to their exceptional selectivity in hydrogenation reactions. This is despite the limited understanding of the physicochemical aspects of hydrogen activation and reaction on Au surfaces. A rational design of new improved catalysts relies on making better use of the hydrogenating properties of Au. This Review analyses the strategies utilized to improve hydrogen-Au interactions, from addressing the importance of the Au particle size to exploring alternative mechanisms for H2 dissociation on Au cations and Au-ligand interfaces. These insights hold the potential to drive future applications of Au catalysis.

Near-edge x-ray absorption fine structure spectra and specific dissociation of small peptoid molecules.

In this study, the total ion yield near-edge x-ray absorption fine structure spectra of four similar peptoid molecules, which differ in the numbers and positions of methyl groups, were investigated experimentally and theoretically. At each excitation energy, the intensity and branching ratio of each ionic product were measured. At a few resonant excitation energies, a specific dissociation of the C-CO bond at the nitrogen and oxygen K-edges and of the N-CO bond at the carbon K-edge was dominant, which correlated well with the predicted destination antibonding orbitals of the core electron excitation. These specific dissociation mechanisms of small peptoid molecules could provide insights into similar phenomena that occur in peptide molecules.

Experimental and kinetic modeling investigation on the co-pyrolysis of benzene, acetylene, and dimethyl ether: Insights into the fuel component interactions

The addition of dimethyl ether (DME) to hydrocarbons is proposed to be a feasible strategy to reduce carbon dioxide emissions in engines. In order to unravel the interaction between hydrocarbons and oxygenated fuels, the co-pyrolysis of benzene, acetylene, and dimethyl ether (DME) is investigated in a flow reactor at 880–1250 K and 1 atm using gas chromatography in this work. Additionally, pyrolysis of pure benzene and co-pyrolysis of benzene and acetylene are also performed. It is observed that the pyrolysis of pure hydrocarbon components and co-pyrolysis of benzene and acetylene can hardly happen in the investigated temperature region, while the addition of DME to the pyrolysis of benzene and acetylene significantly accelerate their decompositions and enhance the formation of key aromatics, such as toluene and indene, showing remarkable synergistic effects on pyrolysis reactivity and aromatics growth. A kinetic model describing the combustion of the three components is developed and used to perform numerical investigation on fuel decomposition and PAH formation. Modeling analysis shows that the addition of DME can effectively activate the pyrolysis system through fast C-O bond dissociation reactions, thereby reducing the decomposition temperatures of benzene and acetylene. The phenyl radical produced from the H-abstraction of benzene can react with acetylene to produce phenylacetylene, while phenylacetylene can further combine with another phenyl radical to form b-phenyl-a-styryl radical which can readily convert to phenanthrene. The addition of DME also generates abundant methyl radical, which further reacts with benzene or other aromatics to form large aromatics such as toluene and methylated PAHs.

Trauma and Dissociation in Young Offenders

AbstractAlthough countless studies provide evidence that many juvenile offences originate from traumatic episodes and consistently demonstrate that exposure to adverse childhood experiences is a significant risk factor for antisocial development, our understanding of the processes that lead some but not all traumatized children to become juvenile offenders is still in progress. By presenting some clinical cases regarding juvenile offenders, the author aims to illustrate how different growth paths, marked by omissive or break‐in experiences, can lead to the same criminal end‐point. The dissociative spectrum mechanisms, the standstill of figurative and symbolic capacity, and the lack of thought resulting from adverse experiences account for the economic and functional underpinnings that lead to juvenile delinquency. For these adolescents, criminal acting represents the ultimate means to neutralize the trauma's attractive force or to mark a boundary to the emotional void left behind by violence or an unsuccessful primary caregiving experience.

Photodissociation of the CH2Br radical: A theoretical study.

Bromine atom (Br) reactions lead to ozone depletion in the troposphere and stratosphere. Photodegradation of bromocarbons is one of the main sources of bromine atoms in the atmosphere. Here, we use high-level abinitio methods, including spin-orbit effects, to study the photodissociation of the CH2Br radical. All possible fragmentation pathways, namely CH2Br + hν → CH2 + Br, HCBr + H, and CBr + H2, have been analyzed. Potential-energy curves of the ground and several excited electronic states along the corresponding dissociating bond distance of each pathway have been calculated. Considering the actinic fluxes of solar irradiation in the troposphere and in the stratosphere in the relevant range of frequencies, it is found that the first five excited states of CH2Br can be accessed from the ground state. Analysis of the potential curves shows that the pathways producing CH2 + Br and HCBr + H can proceed through a fast direct dissociation mechanism, while the pathway leading to CBr + H2 involves much slower dissociation mechanisms like internal conversion between electronic states, predissociation, or tunneling through exit barriers. The main implications are that the two faster channels are predicted to be dominant, and the slower pathway is expected to be less relevant. The tropospheric and stratospheric solar actinic fluxes also allow for further dissociation of the HCBr and CBr fragments, generating additional Br atoms, provided that they survive possible collisions with other atmospheric reagents. Finally, we discuss the possible effect of each of the three CH2Br dissociation pathways on the depletion of atmospheric ozone.

An ab Initio Study of High-Energetic Trioxatriazinane Derivatives: Conformational Analysis, Nitrogen Inversion, Heats of Formation, Dissociation Reaction, and Dimerization.

High-energetic materials belong to two main classes: propellants and explosives. The still rather unexplored family of 1,3,5,2,4,6-trioxatriazinanes, N3O3R3, has a representative of each class. We have selected three compounds, R = H, R = CH3 and R = NO2, this last compound being known as TNTOTA, "trinitro-trioxa-triazinane". Of these compounds we have studied the conformational analysis, the nitrogen inversion, the heats of formation, and the dissociation reaction into the three monomers. In addition, the corresponding 1,3,2,4-dioxadiazetidines (N2O2R2) have also been studied.

Synergy of Dendrites-Impeded Atomic Clusters Dissociation and Side Reactions Suppressed Inert Interface Protection for Ultrastable Zn Anode.

The sluggish ions-transfer and inhomogeneous ions-nucleation induce the formation of randomly oriented dendrites on Zn anode, while the chemical instability at anode-electrolyte interface triggers detrimental side reactions. Herein, this report in situ designs a multifunctional hybrid interphase of Bi/Bi2O3, for the first time resulting in a novel synergistic regulation mechanism involving: (i) chemically inert interface protection mechanism suppresses side reactions; and more fantastically, (ii) innovative thermodynamically favorable Zn atomic clusters dissociation mechanism impedes dendrites formation. Assisted by collaborative modulation behavior, the Zn@Bi/Bi2O3 symmetry cell delivers an ultrahigh cumulative plating capacity of 1.88 Ah cm-2 at 5mA cm-2 and ultralong lifetimes of 300h even at high current density and depth of discharge (10mA cm-2, DODZn: 60%). Furthermore, under a low electrolyte-to-capacity ratio (E/C: 45µL mAh-1) and negative-to-positive capacity ratio (N/P: 6.3), Zn@Bi/Bi2O3||MnO2 full-cell exhibits a superior capacity retention of 86.7% after 500 cycles at 1 A g-1, which outperforms most existing interphases. The scaled-up Zn@Bi/Bi2O3||MnO2 battery module (6V, 1 Ah), combined with the photovoltaic panel, presents excellent renewable-energy storage ability and long output lifetime (12h). This work provides a fantastic synergistic mechanism to achieve the ultrastable Zn anode and can be greatly promised to apply it into other metal-based batteries.

Ribosomal collision is not a prerequisite for ZNF598-mediated ribosome ubiquitination and disassembly of ribosomal complexes by ASCC.

Ribosomal stalling induces the ribosome-associated quality control (RQC) pathway targeting aberrant polypeptides. RQC is initiated by K63-polyubiquitination of ribosomal protein uS10 located at the mRNA entrance of stalled ribosomes by the E3 ubiquitin ligase ZNF598 (Hel2 in yeast). Ubiquitinated ribosomes are dissociated by the ASC-1 complex (ASCC) (RQC-Trigger (RQT) complex in yeast). A cryo-EM structure of the ribosome-bound RQT complex suggested the dissociation mechanism, in which the RNA helicase Slh1 subunit of RQT (ASCC3 in mammals) applies a pulling force on the mRNA, inducing destabilizing conformational changes in the 40S subunit, whereas the collided ribosome acts as a wedge, promoting subunit dissociation. Here, using an in vitro reconstitution approach, we found that ribosomal collision is not a strict prerequisite for ribosomal ubiquitination by ZNF598 or for ASCC-mediated ribosome release. Following ubiquitination by ZNF598, ASCC efficiently dissociated all polysomal ribosomes in a stalled queue, monosomes assembled in RRL, in vitro reconstituted 80S elongation complexes in pre- and post-translocated states, and 48S initiation complexes, as long as such complexes contained≥30-35 3'-terminal mRNA nt. downstream from the P site and sufficiently long ubiquitin chains. Dissociation of polysomes and monosomes both involved ribosomal splitting, enabling Listerin-mediated ubiquitination of 60S-associated nascent chains.

Ring Growth Mechanism in the Reaction between Fulvenallenyl and Cyclopentadienyl Radicals.

Recombination between resonance-stabilized hydrocarbon radicals is an important class of reactions that contribute to molecular growth chemistry in combustion. In the present study, the ring growth mechanism in the reaction between fulvenallenyl (C7H5) and cyclopentadienyl (C5H5) radicals is investigated computationally. The reaction pathways are explored by quantum chemical calculations, and the phenomenological and steady-state rate constants are determined by solving the multiple-well master equations. The primary reaction routes following the recombination between the two radicals are found to be as follows: formation of the adducts, isomerization by hydrogen shift reactions, cyclization to form tricyclic compounds, and their isomerization and dissociation reactions, leading to the formation of acenaphthylene. The overall process can be approximately represented as C7H5 + C5H5 → acenaphthylene + 2H with the bimolecular rate constant of about 4 × 10-12 cm3 molecule-1 s-1. A reaction mechanism consisting of 20 reactions, including the formation, isomerization, and dissociation processes of major intermediate species, is proposed for use in kinetic modeling.