Search

Comprehensive Summary: Bond dissociation energy (BDE), which refers to the enthalpy change for the homolysis of a specific covalent bond, is one of the basic thermodynamic properties of molecules. It is very important for understanding chemical reactivities, chemical properties and chemical transformations. Here, a machine learning‐based comprehensive BDE prediction model was established based on the iBonD experimental BDE dataset and the calculated BDE dataset by St. John et al. Differential Structural and PhysicOChemical (D‐SPOC) descriptors that reflected changes in molecules' structural and physicochemical features in the process of bond homolysis were designed as input features. The model trained with LightGBM algorithm gave a low mean absolute error (MAE) of 1.03 kcal/mol on the test set. The D‐SPOC model could apply to accurate BDE prediction of phenol O—H bonds, uncommon N‐SCF3 and O‐SCF3 reagents, and β‐C—H bonds in enamine intermediates. A fast online prediction platform was constructed based on the D‐SPOC model, which could be found at http://isyn.luoszgroup.com/bde_prediction. [ABSTRACT FROM AUTHOR]

AbstractModeling antioxidants for improved human health is a prime area of research. Inclusion complexes exhibit antioxidant activity. Supramolecular scaffolds like calixtyrosol are anticipated to have considerable antioxidant and therapeutic activity. In this study, we have designed 30 polyphenolic metacyclophanes and investigated their antioxidant properties. Exceptional O─H bond dissociation energy of 44 kcal/mol is reported for a metacyclophane with acyl urea linkage. This may be explained through a cooperative effect of localization of spin density distribution and an intramolecular hydrogen bonding of the corresponding radical. Further, the pharmacokinetics and toxicity analysis screened eight drug-like candidates. The interaction of the eight screened molecules with the Lysozyme transport protein and SOD protein has been studied using the molecular docking approach. Lastly, the MD simulations are performed to analyze the conformational changes of the transport protein after complexation with the proposed molecules. Comprehensive analyses including density functional studies of physiological parameters, favorable pharmacokinetics, toxicity, molecular docking, and MD simulations affirmed polyphenolic metacyclophane XXI as a radical scavenging and drug-like candidate. [ABSTRACT FROM AUTHOR]

The equilibrium nuclear distance is of paramount importance in the study of diatomic molecule properties. It can be obtained through spectroscopic experiments and quantum chemical calculations. The hydrogen molecule (H2) serves as the simplest diatomic molecule, making it an ideal example to illustrate the determination of equilibrium bond distance in homonuclear diatomic molecules. This paper introduces various spectroscopic experimental methods for measuring the equilibrium bond distance, including Raman spectroscopy, electric-field induced dipole spectroscopy, and quadrupole transition spectroscopy. Furthermore, the historical development of solving the Schrödinger equation for the hydrogen molecule, with specific emphasis on the equilibrium bond distance and bond dissociation energy, is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and the structure–activity relationship study of three hydrazone analogs; the Schiff base hydrazone SBH and 2, 4-dinitrophenylhydrazones H1 & H2 derived from (E)-chalcones, to identify the active fragment of each structure. This identification has been carried out following in vitro biological evaluation, which revealed that the analogs H1 and H2 showed significant antibacterial activity due to their (E)-chalcone fragments characterized by proton NMR data and demonstrated by the docked view with emphasis on the involvement of these moieties in the interaction with the DNA gyrase, and thus contributes to the pharmacophore modeling. At the same time, SBH exhibited the highest free radical DPPH scavenging power associated with hydrogen bonding and conjugated push−pull chromophores, which were elucidated by reported vibrational assignments and absorption spectra. The DFT optimizations gave rise to non-planar and distorted structures around the hydrazone group with comparable geometrical parameters. The chemical descriptors predict comparable biological activities, while the BDE necessary for the H-abstraction indicated the best antioxidant activity for the Schiff base hydrazone SBH compound. 2, 4-Dinitrophenylhydrazone analogs with (E)-chalcone and/or push-pull moieties were synthesized and characterized. The in-vitro and in-silico studies were carried out both to find the structure-activity relationship and to model the pharmacophore. [ABSTRACT FROM AUTHOR]

Context: The in-depth understanding about the stability of chemical bonds in energetic compounds plays a central role for molecular design and safety-related evaluations. Most energetic compounds contain nitro as explosophores, and nitro cleavage is fundamental for thermal and mechanical stability. However, the quantum chemistry approach to accurately predict energy and temperature properties related to bond stability is challenging, due to the tradeoff between computational costs and deviations. Herein, the bond orders are proposed as accurate and computational-cost efficient descriptors for predicting the chemical bond stability and thermal-resistant properties. The intrinsic bond strength index (IBSI) demonstrates the best prediction for experimental homolytic bond dissociation energies (R2 > 0.996), which is on par with the results from high-precision quantum chemistry methods. The effects from bond connectivity and steric hindrance hierarchy were analyzed to reveal underlying mechanisms. Additionally, the IBSI descriptors are successfully applied to predict the thermal decomposition temperatures of 24 heat-resistant energetic compounds (R2 = 0.995), thus validating the effectiveness for the prediction and interpretation of chemical bond stability in energetic compounds via a physical organic approach. Methods: All DFT calculations were performed with Gaussian 09 software. To investigate the dependence of the method on functionals and basis sets, 9 DFT methods were considered (B3LYP/6-31G(d,p), B3LYP/6-311G(d,p), B3LYP/def2-TZVP, M062X/6-31G(d,p), M062X/6-311G(d,p), M062X/def2-TZVP, ωB97XD/6-31G(d,p), ωB97XD/6-311G(d,p), and ωB97XD/def2-TZVP). The bond order descriptors LBO and IBSI are obtained through the bond order analysis module in the Multiwfn software. [ABSTRACT FROM AUTHOR]

The knowledge of chemical reactivity of substrates is a prerequisite to accurately design a chemical reaction; however, it has been a challenging task due to the slow trial-and-error experimental approaches and the high computational cost associated with in silico investigations. Artificial intelligence techniques could serve as an alternative to efficiently determine the relative reactivity of chemical entities. In the context of this research, we propose an artificial neural network model to predict the bond dissociation energies of hypervalent iodine reagents. An open-source cheminformatics package, namely, Mordred, was employed for calculating various 1D, 2D and topological descriptors. The approach utilizes a dataset of more than 1000 hypervalent iodine reagents, and the bond dissociation energies can be predicted with a remarkable accuracy, as suggested by an R2 score of 0.97 and a mean absolute error of 1.96 kcal/mol. Owing to the low cost and high efficiency, this machine learning approach can provide an alternative to the theoretical/experimental approaches to rationally design a chemical reaction and without having to go through the hassle of high-throughput experimentation to reach the desired reaction outcome. In an effort to make the model interpretable, a feature importance algorithm was applied, which identified descriptors contributing most to the development of the model. Features describing electronegativity and polarizability are some of the important contributors to the model’s training.

The application of artificial intelligence to chemistry usually focuses on the identification of good correlations between descriptors and a given property of interest. The descriptors often come from arbitrary sets, with the implicit assumption that the evaluation of a sufficiently wide range of descriptors will lead to a satisfactory choice. Recent work in our group has focused on applying statistical analysis to large amounts of DFT results with the goal of finding optimal descriptor sets for a given property, which we label as hidden descriptors. This article briefly discusses this treatment and the chemical knowledge that has been gained through its application in two different domains: metal-ligand bond strength in transition metal complexes, and energy barriers in bimolecular nucleophilic substitution reactions.

Reactions of atomic uranium cations with carbon disulfide form US+ in an efficient exothermic reaction and UCS+ in an inefficient endothermic process. The subsequent reaction of US+ with CS2 forms US2+ in an endothermic process having a low energy threshold. At much higher energies, UCS2+ and UCS+ are also formed. Collision-induced dissociation of US+ with Xe yields U+ + S exclusively in an endothermic reaction. Analysis of the kinetic energy dependent cross sections of the endothermic processes yields the 0 K bond dissociation energies of 5.73 ± 0.15 eV for U+ – S, 3.89 ± 0.08 eV for SU+ – S, 1.69 ± 0.17 eV for U+ – CS, 2.78 ± 0.33 eV for U+ – CS2, 1.53 ± 0.30 eV for SU+ – CS, and 5.65 ± 0.39 eV for S – UCS+. Theory is used to explore the structures and electron configurations of US+, US2+, UCS+, and UCS2+. The thermochemistry measured in this study is further compared to analogous values previously determined for select group 3 metals, lanthanides, and actinides. [ABSTRACT FROM AUTHOR]

Reactions of atomic uranium cations with carbon disulfide form US+ in an efficient exothermic reaction and UCS+ in an inefficient endothermic process. The subsequent reaction of US+ with CS2 forms US2+ in an endothermic process having a low energy threshold. At much higher energies, UCS2+ and UCS+ are also formed. Collision-induced dissociation of US+ with Xe yields U+ + S exclusively in an endothermic reaction. Analysis of the kinetic energy dependent cross sections of the endothermic processes yields the 0 K bond dissociation energies of 5.73 ± 0.15 eV for U+ – S, 3.89 ± 0.08 eV for SU+ – S, 1.69 ± 0.17 eV for U+ – CS, 2.78 ± 0.33 eV for U+ – CS2, 1.53 ± 0.30 eV for SU+ – CS, and 5.65 ± 0.39 eV for S – UCS+. Theory is used to explore the structures and electron configurations of US+, US2+, UCS+, and UCS2+. The thermochemistry measured in this study is further compared to analogous values previously determined for select group 3 metals, lanthanides, and actinides. [ABSTRACT FROM AUTHOR]

We obtain gas-phase homolytic Al-H bond dissociation enthalpies (BDEs) at the CCSD(T)/CBS level for a set of neutral aluminium hydrides (which we refer to as the AlHBDE dataset). The Al-H BDEs in this dataset differ by as much as 79.2 kJ mol-1, with (H2B)2Al-H having the lowest BDE (288.1 kJ mol-1) and (H2N)2Al-H having the largest (367.3 kJ mol-1). These results show that substitution with at least one -AlH2 or -BH2 substituent exerts by far the greatest effect in modifying the Al-H BDEs compared with the BDE of monomeric H2Al-H (354.3 kJ mol-1). To facilitate quantum chemical investigations of large aluminium hydrides, for which the use of rigorous methods such as W2w may not be computationally feasible, we assess the performance of 53 density functional theory (DFT) functionals. We find that the performance of the DFT methods does not strictly improve along the rungs of Jacob's Ladder. The bestperforming methods from each rung of Jacob's Ladder are (mean absolute deviations are given in parentheses): the GGA B97-D (6.9), the meta-GGA M06-L (2.3), the global hybrid-GGA SOGGA11-X (3.3), the range-separated hybrid-GGA CAM-B3LYP (2.1), the hybrid-meta-GGA ÏωB97M-V (2.5) and the double-hybrid methods mPW2-PLYP and B2GP-PLYP (4.1 kJ mol-1). [ABSTRACT FROM AUTHOR]

The bond dissociation energies (BDE) of most main‐group elements have been accurately measured. However, the BDE values for heavy elements, particularly those from the fifth period (InI), are still missing or poorly validated. This study aims to identify the most accurate computational methods for calculating BDE values of compounds containing fifth‐row elements, including In, Sn, Sb, Te, and I, with a focus on readily accessible methods in software packages. The investigation involved a benchmark study using density functional theory (DFT), in addition to the 2nd order Møller–Plesset perturbation theory (MP2) and the coupled cluster with single, double, and perturbative triple excitations CCSD(T). The DFT functionals used in the study include APFD, B3LYP, B3LYP‐D3, B3P86, B97‐D3, BHandH, HSEH1PBE, M06‐2X, MN12‐SX, MN15‐L, and TPSSH. The functionals were carefully selected to cover some popular functionals as well as to cover all levels of the Jacob's ladder of DFT accuracy. The computed BDE values were compared with experimental values, and the results were filtered to remove any possible outliers. The statistical errors (MAPE, RMSE, and Pearson's) were then calculated and used to assess the performance of the methods. [ABSTRACT FROM AUTHOR]

A critical analysis of the literature data on equilibria of gas-phase reactions involving scandium fluorides and calcium and barium monofluorides has been carried out. The most reliable values of ∆fH°(0) for gaseous ScF3 (–1251 ± 15 kJ/mol), ScF2 (–683 ± 10 kJ/mol), and ScF (–141 ± 6 kJ/mol) are recommended. These values and sequential Sc–F bond dissociation energies are in good agreement with the data of quantum mechanical calculations. [ABSTRACT FROM AUTHOR]

Caffeic acid (CAF) i is a polyphenolic compound commonly found in plants, valued for its ability to act as an antioxidant. This study focused on investigating the impact of a natural antioxidant, specifically caffeic acid (CAF), compared to two synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), on the thermal stability of propylene/ethylene copolymer (C-PP/PE), Aiming to establish a theoretical framework for the advancement of novel polymeric antioxidant compounds. Theoretical calculations were conducted to determine each compound's thermodynamic properties and antioxidant activity. The phenolic hydroxyl bond dissociation enthalpy (BDE) values revealed that BHA had the lowest value (325.6 kJ mol−1), trailed by CAF (328.2 kJ mol−1) and BHT (341.3 kJ mol−1), indicating a higher electron-donating capacity of BHA. Transition energy (TS) calculations indicated that BHA had the lowest TS energy (49.29 kJ mol−1), succeeded by CAF (57.61 kJ mol−1) and then BHT (75.57 kJ mol−1), suggesting greater efficiency in radical scavenging. Additionally, the obtained rate constants showed that CAF had the highest hydrogen abstraction rate (k = 1.05 × 10⁵ M⁻1 s⁻1), followed by BHA (k = 1.17 × 10⁴ M⁻1 s⁻1), and then BHT (k = 4.2 × 10³ M⁻1 s⁻1). These results support the effectiveness of CAF as a potentially more active antioxidant. In the experimental part of this study, it was observed that C-PP/PE with BHA showed a lower melt flow index (MFI) (8.51), indicating more excellent thermal stability. On the other hand, samples containing natural caffeic acid extracts exhibited a gradual decrease in MFI with increasing CAF concentration (MFI of 9.4, 8.82, 7.59, 6.44, and 5.98 for concentrations of 0.025, 0.05, 0.075, 0.1, and 0.125 ppm, respectively), suggesting a progressive improvement in the thermal stability of C-PP/PE with increasing natural antioxidant. In TGA analyses, decomposition was observed around 340 °C in samples without additives and those containing 0.1 ppm of BHA. In contrast, samples with different concentrations of CAF showed delayed degradation, observed in the temperature range of 380–400 °C. This delay in degradation indicates that CAF imparts more excellent thermal stability to C-PP/PE copolymer, as it reaches temperatures above 400 °C before starting its decomposition. These findings support the feasibility of using natural antioxidants such as CAF to improve the thermal properties of copolymers.

The purpose of this study is to analyze the reliability of predictive models for higher heating values related to organic materials. A theoretical model was developed, which utilizes bond dissociation energies (BDEs) to establish correlations between elemental composition and calorific values. Our analysis indicates that the energy contribution of one mole of hydrogen atoms is approximately equal to −144.4 kJ mol−1. Further investigation reveals significant variations in the bond dissociation energies of carbon atoms within organic compounds, resulting in a range of energy outputs from −414.30 to −275.34 kJ mol−1 per mole of carbon atoms. The presence of oxygen atoms in organic compounds has a negative impact on the magnitude of combustion heat, with values ranging from 131.1 to 207.17 kJ mol−1. The combustion mechanism imposes certain constraints, leading to the equation HHVg = −31.34·[C] − 144.44·[H] + 10.57·[O] for organic compounds. Based on the parameter sensitivity analysis, the coefficient associated with carbon mass fraction exhibits a significantly greater impact on result prediction accuracy, demonstrating a sensitivity value of 92.65%. The results of further analysis indicate that empirical correlations involving the mass fractions of the elements N and S in lignocellulosic materials may be prone to over-fitting, with sensitivity indices of 1.59% and 0.016%, respectively. [ABSTRACT FROM AUTHOR]

The first results of the hydrogenation of S6-symmetric trifluoromethylfullerene C60(CF3)12 in two types of reactions were reported: (1) high-temperature radical hydrogenation with 9,10-dihydroanthracene and (2) nucleophilic hydrogenation with sodium tetraborohydride under mild conditions. The high-temperature radical hydrogenation of S6-C60(CF3)12 is accompanied by partial elimination of CF3 groups and leads to the formation of a complex mixture of products of a composition C60(CF3)8–12H18–22. During the hydrogenation of NaBH4 under mild conditions, selective formation of the hydride C60(CF3)12H12 was recorded by mass spectroscopy. A kinetic analysis of the sequential nucleophilic hydrogenation of S6-C60(CF3)12 was performed, using quantum-chemical modeling at the level of density functional theory, under the assumption of linear correlation between the activation energy and the enthalpy of elementary steps of the same type. The isomeric composition was predicted for the series of anionic intermediates C60(CF3)12H and their protonation products C60(CF3)12H2n, where n = 1–6. The hydrogenation of S6-C60(CF3)12 should lead to the formation of the thermodynamically and kinetically most stable product ortho-S6-C60(CF3)12H12, in which all hydrogen atoms are located in neighboring positions near the CF3 groups, forming together with them a near-equatorial belt of 24 addends while retaining the triphenylene fragments at two opposite poles. The average bond dissociation energy BDE(C–H) in ortho-S6-C60(CF3)12H12 is 298 kJ mol–1, which is approximately 20 kJ mol–1 higher than the BDE(C–H) of known fullerene hydrides C60H18 and C60H36 (PBE0/def2-SVP). [ABSTRACT FROM AUTHOR]

Context: Plastic waste pyrolysis offers a potential solution to reduce plastic accumulation, but prioritizing monomer recovery from the process is crucial to effectively address the environmental consequences of plastic accumulation. This study focuses on enhancing the yield of styrene during the pyrolysis of polystyrene by investigating thermal and kinetic data. A comprehensive investigation into the thermal degradation pathways of polystyrene is imperative to overcome the challenges associated with its waste management. The calculated bond dissociation energies reveal that the cleavage of non-terminal carbon–carbon bonds is energetically favorable, resulting in the formation of high molecular weight benzylic radicals. Based on these findings, four pyrolysis pathways are proposed, and the associated thermodynamic and kinetic parameters are determined using the DFT method. The major products identified in this study include styrene, α-methylstyrene, isopropylbenzene, methylbenzene, ethylbenzene, and methane. Furthermore, optimizing the temperature profile of the reactor is shown to enhance the recovery of styrene, thereby contributing to the reduction of plastic waste. This study provides valuable insights into the effective resource recovery from polystyrene waste pyrolysis, emphasizing the significance of managing pyrolysis conditions to achieve maximum yield. By controlling the temperature profile during the pyrolysis process, it is possible to obtain a high yield of styrene, facilitating the efficient recovery of the monomer from waste polystyrene and addressing the environmental concerns associated with plastic accumulation. Methods: In this study, all calculations were performed using the B3LYP/6-31G(d) level of theory with the Gaussian 16 program package. The proposed model underwent geometry optimization and frequency calculations. Transition states were optimized using the TS Berny method, and energy profiles along reaction pathways were refined using the QST3 method. The IRC method validated proposed mechanisms and investigated energy profiles. Structural models were visualized using GaussView 6.0. [ABSTRACT FROM AUTHOR]

In this study, the gas-phase homolytic P–F and P–Cl bond dissociation energies (BDEs) of a set of thirty fluorophosphine (R1R2P–F) and thirty chlorophosphine-type (R1R2P–Cl) molecules have been obtained using the high-level W2 thermochemical protocol. For the R1R2P–F species, the P–F BDEs (at 298 K) differ by up to 117.0 kJ mol−1, with (H3Si)2P–F having the lowest BDE (439.5 kJ mol−1) and F2P–F having the largest BDE (556.5 kJ mol−1). In the case of the chlorophosphine-type molecules, the difference in BDEs is considerably smaller (i.e., 72.6 kJ mol−1), with (NC)2P–Cl having the lowest P–Cl BDE (299.8 kJ mol−1) and (HO)2P–Cl having the largest (372.4 kJ mol−1). We have further analyzed the effect of substituents in governing the P–F and P–Cl BDEs by considering the effect of substituents in the parent halogenated precursors (using molecule stabilization enthalpies) and the effect of substituents in the product radicals (using radical stabilization enthalpies). Finally, we have also assessed the performance of a wide range of DFT methods for their ability to compute the gas-phase P–F and P–Cl BDEs contained in this dataset. We find that, overall, the double hybrid functional DSD-PBEB95 offers the best performance for both bond types, with mean absolute deviations of just 2.1 (P–F BDEs) and 2.2 (P–Cl BDEs) kJ mol−1.

Density functional theory (DFT) and the Møller–Plesset expansion (MP2) calculations were benchmarked to characterize the structure of novel derivatives of carbene hydroxymethylene. In this regard, eleven numbers of primary aldehydes including formaldehyde, acetaldehyde, formyl chloride, 2-chloroacetaldehyde, formyl fluoride, 2-fluoroacetaldehyde, formic acid, propionaldehyde, glyoxal, methyl formate, and formyl bromide (1H–11Br) were scrutinized, at the B3LYP/6-311++G(3d,3p) level of theory. Thereafter, the process of keto-enol tautomerism via a [1,2]-H-shift of 1H–11Br was monitored to reach their corresponding enol forms (1P–11P). For all species (except for one structure), the TS involves a triangle structure of C–O–H and yields cis or trans isomers of a singlet ground-state (S) carbene that contrasts the multiplicity of ordinary carbenes. The bond dissociation energy (BDE) calculations were carried out for the homolytic cleavage of C–H bonds of 1H–11Br. The AIM, as a promising analysis that definitely reveals the nature of the bond, was conducted to characterize the eigenvalues at the bond critical points (BCPs). In addition, the relation between the Hammett equation and thermodynamic parameters was obtained. Our investigation suggests new stable S derivatives of carbene hydroxymethylene that can be isolated. [ABSTRACT FROM AUTHOR]

The density functional theory method was used to calculate the bond dissociation energy of polybutylene terephthalate（PBT） dimer. In order to select a relative accurate method to calculate the bond dissociation energy of PBT, the ethyl acetate, which has the same ester functional group as PBT, was selected as the model reference to calculate the bond dissociation energies by using M062 X, B3 P86, M06, PBE0 and wB97 xD methods with the basis sets of 6-31 G（d）, 6-311 G（d）, 6-311+G（d, p）, 6-311++G（d, p）, cc-pVDZ and cc-pVTZ, respectively. By comparing the calculated results with the measured values of the ethyl acetate experiment in the iBonD database, it can be seen that the calculated results of M062 X at the level of 6-311 G（d） basis set are closest to the experimental values. Therefore, the M062 X method was used to calculate the bond dissociation energy of PBT dimer at the level of 6-311 G（d） basis set in this study. The calculated results show that the C-Carcmatic bond has the largest bond dissociation energy among the bonds of PBT, the bond dissociation energy of C-C bond on the main chain is the smallest, which is 370.9 kJ/mol, followed by the C-O bond, which is 404.6 kJ/mol. Based on the calculated results of the dissociation energy of the PBT, three possible reaction paths during the thermal degradation of the PBT dimer are designed, and the formation mechanism of the pyrolysis products was analyzed. The results indicate that the pyrolysis process of PBT dimer may mainly undergo a concerted reaction. [ABSTRACT FROM AUTHOR]

Flavonols are compounds with radical-scavenging activities that can prevent the harmful effects of free radicals. Their radical-scavenging activity has attracted significant attention. Recently, quantum chemistry-based methodologies have significantly improved the understanding of the activity due to dramatic increases in computational power and software improvements. A standardized analysis method for estimating radical scavenging activity, the quantum mechanics-based test for overall free radical scavenging activity (QM-ORSA), has been proposed. An obstacle in applying the QM-ORSA protocol to flavonols is the large number of conformers and hydroxy groups for analysis. In this study, we focused on it and analyzed the conformational dependences of three flavonols (myricetin, quercetin, and kaempferol) on their chemical properties: bond dissociation energy, pKa, and ionization energy. As a result, all chemical properties were insensitive to conformational differences. The conformational search should be performed separately for each in the gas phase and in aqueous solution because of the differences in the major conformer (relative population of each conformer). These results suggest that it is important to perform the conformational search separately in water and in the gas phase and to determine one representative structure for analyzing radical scavenging activity.

Atom transfer radical polymerization (ATRP) is a versatile & famous technique for the synthesis of well defined molecular architectures. In ATRP, there is a dynamic equilibrium exists between active & dormant species. Therefore, ATRP progress through a sequence of activation & deactivation cycles, ending upon complete monomer consumption & termination reactions are minimized. This paper presents a systematic computational study on kinetics & thermodynamics associates in the ATRP of itaconimide monomers & methyl methacrylate (MMA). For this, the copolymerization system is modeled as a unimer, dimer & trimer of various itaconimides & MMA monomer. The density functional theory with B3LYP functional & 6–31 + G(d)/LanL2DZ basis sets is used in the prediction of geometries & energetics associated with the dissociation of terminal R–X bond present in the unimer, dimer & trimer. The relative equilibrium constant (KATRP) for the ATRP activation/deactivation steps is calculated from the free energy values associated with dissociation of R–X bond. The relative KATRP values of dimer & trimer of selected monomers is compared with their respective unimer. From the transition state geometries of the dimeric propagating radical, activation energy is calculated. The gas phase rate coefficients for propagation (kp) (of itaconimides & MMA copolymerization) are calculated using the standard transition state theory. The effect of system parameters such as solvent, temperature & substituent on KATRP & kp values of dimer is investigated systematically. The change in the initiating system & temperature has significant effect on kp values as compared to solvent & various substituent. The KATRP values of dimer & trimer dormant species are higher as compared to their respective monomeric species. The neighboring monomer & penultimate monomer plays vital role in kinetics & thermodynamics associated with copolymerization. The obtained initial results show that the mechanism of copolymerization of itaconimide monomers & MMA follows penultimate model. [ABSTRACT FROM AUTHOR]

Carbon‐Carbon bond forming reactions are ubiquitous in nature and important for chemical and drug synthesis. Modern methods mostly utilize activated reactants, and despite recent developments in organic synthesis, and theoretical understanding, these have had limited success with unactivated C−H bonds. Here we apply a simple yet powerful Bond Dissociation Energy (BDE)‐based Reaction Enthalpy (BDERE) analysis to model C−C cross‐coupling reactions. BDERE appears in classical textbooks (halogenation of alkanes) but has not been applied to cross‐coupling reactions. BDERE allows one to rationalize the ease of coupling reactions for both homolytic and heterolytic mechanisms for all six C−C bond hybridization types. It facilitates the identification of a simple but unexplored reaction for ethane synthesis. BDERE values give valuable insights into recent advancements in C−C cross‐couplings of fully unfunctionalized (UFCC) and semi‐functionalized (SFCC) reactants that utilize metal, photoredox, organo, and biocatalysis. BDERE analysis may enable others to investigate and design novel cross‐coupling reactions. [ABSTRACT FROM AUTHOR]

In this work, the bond dissociation energy (BDE) values, including BDE(O−X) and BDE(N−O), for 129 alkoxyamines (XRT) of TEMPO derivatives were predicted, and the evaluations on stabilities of alkoxyamines, reactivities of alkoxyamines as radical donors and reactivity of TEMPO as various radical scavenger are well compared and discussed based on the predicted BDE values from the view of thermodynamic driving forces. Without a doubt, the wide and valuable BDE values are helpful for chemists better understand the thermodynamic properties and kinetic behaviors of alkoxyamines and TEMPO in chemical reactions and drug metabolism in vivo and promoting the rapid development and application of novel alkoxyamines. [ABSTRACT FROM AUTHOR]

Flavonols are compounds with radical-scavenging activities that can prevent the harmful effects of free radicals. Their radical-scavenging activity has attracted significant attention. Recently, quantum chemistry-based methodologies have significantly improved the understanding of the activity due to dramatic increases in computational power and software improvements. A standardized analysis method for estimating radical scavenging activity, the quantum mechanics-based test for overall free radical scavenging activity (QM-ORSA), has been proposed. An obstacle in applying the QM-ORSA protocol to flavonols is the large number of conformers and hydroxy groups for analysis. In this study, we focused on it and analyzed the conformational dependences of three flavonols (myricetin, quercetin, and kaempferol) on their chemical properties: bond dissociation energy, pKa, and ionization energy. As a result, all chemical properties were insensitive to conformational differences. The conformational search should be performed separately for each in the gas phase and in aqueous solution because of the differences in the major conformer (relative population of each conformer). These results suggest that it is important to perform the conformational search separately in water and in the gas phase and to determine one representative structure for analyzing radical scavenging activity. [ABSTRACT FROM AUTHOR]

Calculations with high accuracy for atomic and inter-atomic properties, such as nuclear magnetic resonance (NMR) spectroscopy and bond dissociation energies (BDEs) are valuable for pharmaceutical molecule structural analysis, drug exploration, and screening. It is important that these calculations should include relativistic effects, which are computationally expensive to treat. Non-relativistic calculations are less expensive but their results are less accurate. In this study, we present a computational framework for predicting atomic and inter-atomic properties by using machine-learning in a non-relativistic but accurate and computationally inexpensive framework. The accurate atomic and inter-atomic properties are obtained with a low dimensional deep neural network (DNN) embedded in a fragment-based graph convolutional neural network (F-GCN). The F-GCN acts as an atomic fingerprint generator that converts the atomistic local environments into data for the DNN, which improves the learning ability, resulting in accurate results as compared to experiments. Using this framework, the 13 C/ 1 H NMR chemical shifts of Nevirapine and phenol O–H BDEs are predicted to be in good agreement with experimental measurement. [ABSTRACT FROM AUTHOR]

In order to reduce the vulnerability, the responses to shock waves for booster explosives JO9C, JH14, JH6, and insensitive RDX were evaluated using shock wave partition loading test. To explain the experimental results, molecular dynamics simulation, intermolecular interaction and bond dissociation energy (BDE), and shock initiation pressures were evaluated using the B3LYP, MP2 (full), and M06-2X methods with the 6–311 + + G(2df,2p) basis set. The order of the responsivity is JO9C > JH14 > JH6 > insensitive RDX. The binding energies follow the order of JH14* ≈ JO9C* < insensitive RDX* < JH6*. The interaction energies and BDEs are in RDX∙∙∙(CH3COOCa)+ > RDX∙∙∙CH3COOH > RDX∙∙∙CH2FCH2F. Thus, it can be inferred that for the RDX-based explosives, the stronger the binding energy, intermolecular interaction, and BDE are, the more insensitive the booster is, and thus, the larger energy has to be consumed to overcome the above three kinds of energies during the initiation process, leading to the smaller energy output and weaker response. However, it should be noted that it is mainly the density and the type of explosive that influence the depth of the dent produced on the steel witness block. The essence of the responses to shock waves is revealed by the reduced density gradient, atoms in molecules, and surface electrostatic potentials. Highlights: • Response of booster to shock wave was evaluated by shock wave partition loading test. • Responsivity to shock wave is explained by binding energy, intermolecular interaction, and BDE. • Shock initiation pressures were evaluated. • Essence of responses to shock wave is revealed by RDG, AIM and ESP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Key factors for lignin dissociation are investigated by DFT and machine learning. • Oxidating C α -OH to C α = O in lignin benefits the cleavage of β-O-4 and β-1 bonds. • Hydroxyl and methoxy benefit the cleavage of C β -1 and C α -C β bonds in β-1 dimer. • Chlorine atoms substituting in the benzene ring favor the cleavage of β-O-4 bond. • n-Hexane favors the cleavage of C α -C β bond while water has the opposite effect. The bond dissociation energy (BDE) of lignin is a key factor for lignin depolymerization, assisting in revealing the depolymerization mechanism. However, the impact of substituent as well as solvent, which usually stay together, on BDE of lignin remains unclear. Here, density functional theory (DFT) calculation is employed to compute the BDE of C–O and C–C bonds in lignin oligomers with six substituents in four solvents. The relationship models between multiple factors and BDE are established using random forest algorithm, achieving a predictive accuracy of 0.97. The results show that oxidating hydroxyl to ketone benefits the cleavage of β-O-4 and β-1 bonds. Hydroxyl and methoxy effectively contribute to breaking the C β -1 and C α –C β bonds in the β-1 dimer. Polar solvents combined with hydroxyl promote C–O bond dissociation, while alkyl-containing solvents favor C–C bond dissociation. These findings provide valuable insights into lignin depolymerization, pre-depolymerization structural modifications, and the prediction of depolymerization pathways. [ABSTRACT FROM AUTHOR]

Aluminum oxide is a widely recognized structural ceramic material known for electrical insulation and wear/corrosion resistance. Recent studies have challenged the conventional perception of brittleness by uncovering remarkable plasticity in amorphous aluminum oxides. To further enhance the fracture toughness of aluminum oxides and expand their applications in fields requiring resistance, it is crucial to analyze the factors influencing the tensile deformation process and investigate the underlying origins of ductility. In this study, molecular dynamics simulations were employed to compare the ductility of amorphous aluminum oxides with crystalline aluminum oxides and other amorphous ceramic oxides. Our findings indicate that the degree of crystallinity significantly influences ductility. Moreover, the simulations revealed that amorphous aluminum oxides exhibit the highest total elongation among binary structural ceramic oxides such as TiO 2 and SiO 2 , underscoring the intrinsic plasticity of aluminum oxide. Furthermore, we discovered that aluminum oxides possess a low bond-dissociation energy (E BD) compared to other structural ceramic oxides, leading to a higher occurrence frequency of plastic deformation mechanisms. Based on these observations, low E BD could be proposed as the probable indicator that enables the estimation of ductility of structural amorphous oxides without resorting to complex atomistic simulations. This quantitative criterion, based on an easily accessible material property, provides valuable guidance for predicting the ductility of newly-designed structural ceramic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze the reliability of predictive models for higher heating values related to organic materials. A theoretical model was developed, which utilizes bond dissociation energies (BDEs) to establish correlations between elemental composition and calorific values. Our analysis indicates that the energy contribution of one mole of hydrogen atoms is approximately equal to −144.4 kJ mol−1. Further investigation reveals significant variations in the bond dissociation energies of carbon atoms within organic compounds, resulting in a range of energy outputs from −414.30 to −275.34 kJ mol−1 per mole of carbon atoms. The presence of oxygen atoms in organic compounds has a negative impact on the magnitude of combustion heat, with values ranging from 131.1 to 207.17 kJ mol−1. The combustion mechanism imposes certain constraints, leading to the equation HHVg = −31.34·[C] − 144.44·[H] + 10.57·[O] for organic compounds. Based on the parameter sensitivity analysis, the coefficient associated with carbon mass fraction exhibits a significantly greater impact on result prediction accuracy, demonstrating a sensitivity value of 92.65%. The results of further analysis indicate that empirical correlations involving the mass fractions of the elements N and S in lignocellulosic materials may be prone to over-fitting, with sensitivity indices of 1.59% and 0.016%, respectively.

This report presents the N–H and O–H bond dissociation energies (BDEs) and enthalpies (BDEts) of 27 para-substituted anilines and phenols using Density Functional Theory (DFT) with functional wB97X-D and basis set 6-31G**. The computed BDEs/ BDEts show a strong correlation with the calculated rotational barrier (RB) around phenyl–NH2 and phenyl–OH bonds of the parent neutral molecules. Electron-withdrawing (EW) substituents increased RB and BDEs/BDEts, while electron-donating (ED) substituents caused opposite behavior. Geometric, atomic, molecular, and spectroscopic properties of NH2 and OH groups in neutral anilinic and phenolic molecules exhibited excellent correlations with RB and BDEs/BDEts. The geometry around heteroatoms of the radicals displayed constant geometrical changes for all substituents. Spin density maps confirmed that the unpaired electrons in radicals are delocalized in heteroatoms and phenyl rings for all the para-substituents. Spin delocalization in both types of radicals was further enhanced in the presence of para-ED substituents. The increase in electronic density around heteroatoms of radicals with the strength of ED substituents was found proportional to that in neutral molecules. Therefore, the N–H and O–H BDE/BDEt are mainly governed by the stabilization/destabilization of the neutral molecules and, to a significantly lower extent, the stabilization of radicals in the case of strong ED groups.

Recently, molecular hydrogen has been found to exhibit antioxidation activity through many clinical experiments, but the mechanism has not been fully understandable at atomic level. In this work, we perform systematic ab initio calculations of protoheme-hydrogen complexes to clarify the antioxidation mechanism of molecular hydrogen. We make molecular modeling of iron–protoporphyrin coordinated by imidazole, FeP(Im), and its hydrogen as well as dihydrogen complexes, together with reactive oxygen/nitrogen species (RONS). We carry out structural optimization and Mulliken charge analysis, revealing the two kinds of bonding characteristics between FeP(Im) and H 2 : dihydrogen bonding in the end-on asymmetric configuration and Kubas bonding in the side-on symmetric configuration of H 2 molecule. The activation barriers for adsorption and dissociation of H 2 on and further desorption of H atom from FeP(Im) are found to be below 2.78 eV at most, which is remarkably lower than the H–H bond breaking energy of 4.64 eV in free H 2 molecule. We find that the hydrogen bond dissociation energies of FeP(Im)–H 2 and –H complexes are lower than those of RONS–H complexes, indicating the decisive role of protoheme as an effective catalyst in RONS antioxidation by molecular hydrogen in vivo. [ABSTRACT FROM AUTHOR]

We have quantum chemically investigated how methyl substituents affect the stability of alkyl radicals MemH3−mC⋅ and the corresponding MemH3−mC−X bonds (X = H, CH3, OH; m = 0 – 3) using density functional theory at M06‐2X/TZ2P. The state‐of‐the‐art in physical organic chemistry is that alkyl radicals are stabilized upon an increase in their degree of substitution from methyl

Avenanthramides, the phenolic antioxidants exclusively found in oats (Avena sativa L.), have long been recognized for their immense health benefits owing to their antioxidant potential. Herein, hydroperoxyl radical (•OOH) scavenging activity of oat avenanthramides is investigated in detail, using density functional theory for the first time. Three probable mechanisms: (a) hydrogen atom transfer (HAT), (b) single electron transfer followed by proton transfer, and (c) sequential proton loss electron transfer (SPLET), are considered towards evaluating the antioxidant potential of avenanthramides (A–C) in the gas phase as well as in both polar and non‐polar media. Based on the computed data, HAT is found to be the thermodynamically preferred mechanism for antioxidant activity in the gas phase. In the polar medium, SPLET represents the most probable reaction pathway. Our thermodynamic and kinetic data computed at the B3LYP level predict avenanthramide C, characterized by an ortho‐dihydroxy functionality on the aromatic ring, as the most potent radical scavenger among the three variants, in agreement with the available experimental reports. [ABSTRACT FROM AUTHOR]

Plastics serve as an essential foundation in contemporary society. Nevertheless, meeting the rigorous performance demands in advanced applications and addressing their end-of-life disposal are two critical challenges that persist. Here, an innovative and facile method is introduced for the design and scalable production of polycarbonate, a key engineering plastic, simultaneously achieving high performance and closed-loop chemical recyclability. The bisphenol framework of polycarbonate is strategically adjusted from the low-bond-dissociation-energy bisphenol A to high-bond-dissociation-energy 4,4'-dihydroxydiphenyl, in combination with the incorporation of polysiloxane segments. As expected, the enhanced bond dissociation energy endows the polycarbonate with an extremely high glow-wire flammability index surpassing 1025 °C, a 0.8 mm UL-94 V-0 rating, a high LOI value of 39.2%, and more than 50% reduction of heat and smoke release. Furthermore, the π-π stacking interactions within biphenyl structures resulted in a significant enhancement of mechanical strength by as more as 37.7%, and also played a positive role in achieving a lower dielectric constant. Significantly, the copolymer exhibited outstanding closed-loop chemical recyclability, allowing for facile depolymerization into bisphenol monomers and the repolymerized copolymer retains its high heat and fire resistance. This work provides a novel insight in the design of high-performance and closed-loop chemical recyclable polymeric materials., (© 2024 Wiley‐VCH GmbH.)

The bonding between copper and epoxy resin is investigated using a CHSi thin film to achieve highly adhesive and reliable bonding between the resin mold and the copper substrate in power modules. In this study, high-temperature (473 K) testing is performed to improve the reliability of this junction after high-temperature operation. The bond strength decreases and delamination occurs at the filmcopper interface after high-temperature testing. The decrease in bond strength may be due to the decrease in the filmcopper interfacial strength because of the decrease in the binding force between copper and oxygen upon heating. When Fe and Cr, which have high oxygen bond disassociation energies, are intercalated at the filmcopper interface, the bond strength improves after high-temperature testing and a bond strength above 30MPa was retained after 1000 h. This study is a novel method of dissimilar bonding based on chemical and physical effects of CHSi film existing between copper and resin. Further, it is an effective method of bonding to achieve high-temperature operation of a resin-molded power module, which can contribute to future advancements in power electronics products. [ABSTRACT FROM AUTHOR]

In this study, the performance of 17 different density functional theory functionals was compared for the calculation of the bond dissociation energy (BDE) values of X−H (X=C, N, O, S) bonds of aromatic compounds. The effect of the size of the basis set (expansions of 6-31(G)) was also assessed for the initial geometry and zero-point energy calculations, followed by the single-point BDE calculations with different model chemistries with the 6-311 + (3df,2p) basis set. It was found that the size of the basis set for geometry optimization has a much smaller effect on the accuracy of BDE than the choice of functional for the following single-point calculations. The M06-2X, M05-2X and M08−HX functionals yielded highly accurate BDE values compared to experimental data (with the average mean unsigned error MUE = 1.2–1.5 kcal mol−1), performing better than any of the other functionals. The results suggest that geometry optimization may be performed with B3LYP functional and a small basis set, whereas the M06-2X, M05-2X and M08-HX density functionals with a suitably large basis set offer the best method for calculating BDEs of ArX−H (X=C, N, O, S) bonds.

Aromatic amines, the widely used raw materials in industry, cause long-term exposure to human bodies. They can be metabolized by cytochrome P450 enzymes to form active electrophilic compounds, which will potentially react with nucleophilic DNA to exert carcinogenesis. The short lifetime and versatility of the oxidant (a high-valent iron (IV)-oxo species, compound I) of P450 enzymes prompts us to use theoretical methods to investigate the metabolism of aromatic amines. In this work, the density functional theory (DFT) has been employed to simulate the hydroxylation metabolism through H-abstraction and to calculate the activation energy of this reaction for 28 aromatic amines. The results indicate that the steric effects, inductive effects and conjugative effects greatly contribute to the metabolism activity of the chemicals. The further correlation reveals that the dissociation energy of -NH2 (BDEN-H) can successfully predict the time-consuming calculated activation energy (R2 for aromatic and heteroaromatic amines are 0.93 and 0.86, respectively), so BDEN-H can be taken as a key parameter to characterize the relative stability of aromatic amines in P450 enzymes and further to quickly assess their potential toxicity. The validation results prove such relationship has good statistical performance (qcv2 for aromatic and heteroaromatic amines are 0.95 and 0.90, respectively) and can be used to other aromatic amines in the application domain, greatly reducing computational cost and providing useful support for experimental research.

We discuss the physical criteria that have been proposed as a measure of the strength of a chemical bond. Critical examination of the strengths and weaknesses of the various quantities shows that the force constant is the most general measure for determining the strength of a chemical bond in molecules. The force constant of a bond AB is a direct indicator of the interatomic forces between the fragments A and B at the equilibrium distance, which is independent from the energies and electronic structures of the free species A and B. This is a great advantage compared to the use of energy differences for determining the bond strength, which are subject to the choice of the reference system that is often not uniquely defined. This is particularly evident when considering the strength of a chemical bond in strongly bonded but metastable species such as [O2]2+. The change in the electronic structure of the reference system obscures the intrinsic bond strength at equilibrium. Energy changes along the course of chemical reactions are elementary quantities in chemistry; they provide crucial information for the kinetics and thermodynamics of processors. However, they are not suitable as a measure of bond strength. The definition of local vibrational constants by Konkoli and Cremer eliminates the coupling of the stretching vibration with other vibrational modes, which makes it possible to use force constants as direct measure for bond strength also in larger molecules. [ABSTRACT FROM AUTHOR]

Oxidative stress that damages cellular components affects various organs including the brain. It is thus believed to play an active role in neurodegenerative diseases, wherein the intrinsic antioxidant enzymes metabolize toxic intermediates. For therapeutic purpose, instead of antioxidant enzymes, small organic compounds as antioxidants may be more effective. Here, reducing power and electrochemical behavior of some flavanols, flavanonols, flavones, flavonols and O–methylated flavonols have been estimated and confirmed by the calculated bond dissociation energy. Compared to other classes, flavonols exhibited increased reducing power that decreased with methylation of the oxygen atom in the B-ring. Gossypetin emerged as the most effective of these flavonols. Generally, compounds with two hydroxyl groups in two consecutive positions of the phenyl ring and an enolic group in the C-ring with more preference for the hydroxyl group in the ortho position with respect to each other in the catechol moiety showed major activity. 5 position of the A-ring showed the least effect on the activity. The present understanding therefore may be applied for identifying compounds to be used as scaffold for designing potent antioxidants. [ABSTRACT FROM AUTHOR]

The interaction of N‐heterocyclic carbene (NHC) ligands with transition metal centers is analyzed with a set of descriptors derived from the statistical treatment of density functional theory (DFT) computational results. These descriptors, labeled as hidden descriptors (HD), had been previously defined in our group and here are applied with the help of a user‐friendly web application developed for that purpose: BDE Matrix App. Five HDs are computed with little computational effort for each NHC under consideration. Expectations are confirmed in that the binding to the metal center is largely ruled by the first two descriptors, suitably associated to σ donation and π backdonation, and the approach leads to a straightforward comparison of their quantitative values. The study is extended beyond NHCs, and other neutral ligands, such as cyclopropenylidenes, phosphines, and amines are considered. The procedure is shown to be well suited to provide a unified framework for the comparison of these diverse ligands. [ABSTRACT FROM AUTHOR]

Proton dissociation property and chemical stability of precisely sulfonated polyethylene, p21SA, has been investigated by theoretical calculations. The results show that proton in model compound is spontaneously dissociated when hydration number is 3, while in a folded structure, only required a hydration number of 2.5, lower than Nafion. Evidently, its good proton dissociation property and folded structure are contributed to the outstanding proton conductivity of p21SA. The chemical stability of p21SA membrane is evaluated by the bond dissociation energy and chemical degradation mechanism calculations, which discloses that C–S bond is the weakest for p21SA backbone. The most favorable degradation routes are H atom abstraction by radicals followed by C–S bond scission. We hope this work can provide some ideas for the performance improvement of p21SA membrane analogues used in proton electrolyte membrane fuel cells. • Excellent proton dissociation contributed to the high proton conductivity of p21SA. • The folded structure of p21SA improves the proton dissociation property. • C–S bond is the most fragile site towards radical attack in p21SA membrane. [ABSTRACT FROM AUTHOR]

Bi‐ and tricyclic derivatives 1 a and 2 a (Scheme 2) combining the catalytic N‐hydroxyimide NO−H unit with the imidazole moiety were designed as multipurpose derivatives and proposed as chemical tools for achieving improved homogeneous and heterogeneous aerobic oxidation catalysis. BDE tunability, formation of a ZIF and of imidazolium ionic‐liquid‐like materials were obtained for N‐hydroxyphthalimide (NHPI)‐based 2 a and here described. [ABSTRACT FROM AUTHOR]

The atomic and molecular properties of the title compounds were calculated by Jaguar using a basis set B3LYP/6-31G**++ with hybrid DFT in the gas phase, to determine the chemical reactivity. Analysis of quantum chemical features such as HOMO and LUMO explained that the electronic charge transfer occurred within the system through conjugated paths of the selected compounds. The nucleophilic and electrophilic reactive sites are recognized from the molecular electrostatic potential plot. Electrophilic and nucleophilic attack-prone molecular sites were predicted by mapping ALIE value to the molecular surface. The bond dissociation energy of the high active compound 15 (2-chloro-N-(2-(2-(2-(2-chlorobenzoyl)hydrazineyl)-2-oxoethoxy)phenyl)acetamide) was calculated to assess the probability of compound autoxidation or degradation. Further, molecular docking, binding free energy calculations, and ADMET profile of the degradation products (DPs) of compound 15 was carried out to determine the binding affinity and toxicity profile of the formed DPs compared with the parent compound. A 150-ns molecular dynamics (MD) simulation was performed to evaluate the binding stability of the compound 15/4URL complex using Desmond. Binding free energy and binding affinity of the complex were computed for 100 trajectory frames using the MM-GBSA approach. [ABSTRACT FROM AUTHOR]

The development of new resins with high heat resistance and excellent processing properties is of great significance to aerospace, communications, and electronics fields. In this work, density functional theory (DFT) is used to systematically study the bond dissociation energy (BDE) of main bonds in a series of new heat-resistant silane-arylacetylene resin, aromatic heterocyclic-containing resin, and cyano-containing resin molecules. The DFT-B3LYP functional and 6-31g(d,p) basis set are adopted to make all resin molecules relax fully. The vibrational analysis results show that all resin molecules have no imaginary frequency, indicating that they correspond to the stable configuration on their potential energy surfaces. Then, BDEs of the main chemical bonds in all resin molecules are calculated. This work mainly studies the thermal stability of resin monomer molecules, so the thermal stability of the monomer molecules can be measured by calculating BDE of the main bonds in the resin monomer molecules. In fact, the curing reaction of the resin monomer molecules at high temperature usually occurs on the branches, while the ring remains unchanged. The heterocyclic ring and benzene ring are aromatic, and BDEs of the bonds on the rings are higher than those of the non-cyclic bonds. Therefore, BDEs of the bonds on the rings in the resin monomer molecules are not considered in this work. At the same time, the reactants and free radical products are optimized and the vibrational analysis is performed. The results show that the cyano-containing resin molecules have higher thermal stability than the silane-aryne-containing resin molecules and aromatic heterocyclic-containing resin molecules, indicating that the introduction of cyano groups into the resin molecules is more helpful for improving their thermal stability than the introduction of silane-arylalkynyl and aromatic heterocycles groups. Our studies find the weakest bond in each resin molecule and reveal the essence of its thermal stability at the microscopic level, which provide a theoretical basis for the design, synthesis, and application of new high temperature resistant resins. [ABSTRACT FROM AUTHOR]

1-((Cyano-1-methylethyl) azo) formamide (CABN) is an azo initiator that has the inherent property of being decomposed at high temperatures with considerable amounts of heat generated. The thermal hazard of CABN is the main consideration in the occurrence of serious accidents. In this study, differential scanning calorimetry (DSC) was used to obtain the heat flow profiles and thermodynamic parameters of pure and impure CABN at various heating rates. The gaseous products and decomposition residues corresponding to each mass loss stage of CABN were judged by a thermogravimetry-mass spectrometer (TG-MS) and infrared spectrometer (IR). The optimal thermal decomposition reaction path of CABN was simulated and determined by the Gaussian software. The Materials Studio software was used to simulate the front-line orbits and energy gaps of CABN and its mixture to determine the influence of impurities on the thermal stability of CABN. Above results showed that the addition of the impurities caused an increased thermal decomposition risk of CABN. N 2 , CO, CO 2 , CH 4 N 2 O, 2-aminoisobutyronitrile, and isobutyronitrile were the potential products as a result of the thermal decomposition of CABN. The results of this study are expected to provide the fundamentals for safely handling CABN in preparation, production, transportation, and storage purposes. [ABSTRACT FROM AUTHOR]