Low Bond Dissociation Energy Research Articles

Cold Molecular Ions via Autoionization below the Dissociation Limit.

Several diatomic transition metal oxides, rare-earth metal oxides, and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6)eV above the ionization energy.

Acyl Iodide Synthesis from Carboxylic Acids Using a Novel Ph2P(O)H‐I2 Binary System and Its Application to Facile Preparation of Amides, Esters, and Thioesters

AbstractAcyl iodides are expected to be excellent acylating agents due to the low bond dissociation energy of the carbon–iodine bond and the high capability of iodine as a leaving group. Unfortunately, the preparative methods for acyl iodides directly from carboxylic acids are rather limited. In this work, we found that a novel binary system combining I2 and diphenylphosphine oxide (Ph2P(O)H) provides a simple method for the preparation of acyl iodides from carboxylic acids. Furthermore, the subsequent one‐pot reaction with appropriate nucleophiles, such as amines, alcohols, and thiols, afforded the corresponding amides, esters, and thioesters, respectively, in good to excellent yields.

Catalyst-Controlled Strategies to Override the Bond Dissociation Energy-Driven Selectivity of Benzylic C(sp3)–H Insertions

AbstractCatalytic C(sp3)–H insertion reactions of arylalkanes generally proceed at the benzylic position as a consequence of the lower bond dissociation energy (BDE) of the corresponding C–H bond. This account gives a brief overview of recent studies aimed at designing catalyst-controlled amination reactions to go beyond this BDE-driven selectivity. They permit the selective conversion of neutral C–H bonds with a BDE greater than 95 kcal mol–1 for the formation of alkylamines.1 Introduction2 Catalyst-Controlled Site-Selective C–H Insertion Reactions3 Catalyst-Controlled Intermolecular Amination of Nonactivated C–H Bonds of Arylalkanes4 Conclusion

Photo-reductive decomposition of perfluorooctane sulfonate (PFOS) and its common alternatives by UV/VUV/sulfite process: Mechanism, kinetic modeling, and water matrix effects

The present study investigated the photo-reduction of perfluorooctane sulfonate (PFOS) and its alternatives, focusing on decomposition mechanisms, active species involvement, the influence of background water constituents, and kinetic model development. The decomposition and defluorination rates followed the order of PFOS > PFHxS > 6:2 FTSA > PFBS, with shorter chains and CH2 linkers enhancing the resistance of PFOS alternatives against the attack of hydrated electrons (eaq−). Two primary pathways were identified during the photodegradation of PFAS: (i) H/F exchange at CF bonds with the lowest bond dissociation energies (BDEs) and (ii) functional group cleavage followed by short-chain PFCAs formation, with OH playing a crucial role in transforming intermediates. Adding iodide and elevated temperatures demonstrated a synergistic effect on PFBS decomposition and defluorination, with high temperatures promoting functional group cleavage as the preferred defluorination pathway. The study examined the impact of background water constituents in different aqueous environments, from surface waters to wastewater streams and ion-exchange brine concentrates. Chloride exhibited a concentration-based dual impact on the UV/VUV/sulfite process: promotive effects at low dosages (1–10 mM) by acting as a secondary eaq− mediator, and adverse effects at high dosages (20–500 mM) due to the scavenging effect of generated chlorine radicals (Cl). High ionic strength adversely affected eaq− quantum efficiency. Additionally, bicarbonate and natural organic matter (NOM) had opposing effects on PFOS photo-reduction, primarily through eaq− scavenging and pH alteration. Kinetic modeling revealed reaction rate constants of the studied PFAS with eaq− ranging from 1.8 × 106 to 1.3 × 109 M−1 s−1, corroborating the concentration profiles of active species and highlighting the reductive nature of sulfite-mediated processes.

Sulfotransferase-mediated phase II drug metabolism prediction of substrates and sites using accessibility and reactivity-based algorithms.

Sulphotransferases (SULTs) are a major phase II metabolic enzyme class contributing ~20 % to the Phase II metabolism of FDA-approved drugs. Ignoring the potential for SULT-mediated metabolism leaves a strong potential for drug-drug interactions, often causing late-stage drug discovery failures or black-boxed warnings on FDA labels. The existing models use only accessibility descriptors and machine learning (ML) methods for class and site of sulfonation (SOS) predictions for SULT. In this study, a variety of accessibility, reactivity, and hybrid models and algorithms have been developed to make accurate substrate and SOS predictions. Unlike the literature models, reactivity parameters for the aliphatic or aromatic hydroxyl groups (R/Ar-O-H), the Bond Dissociation Energy (BDE) gave accurate models with a True Positive Rate (TPR)=0.84 for SOS predictions. We offer mechanistic insights to explain these novel findings that are not recognized in the literature. The accessibility parameters like the ratio of Chemgauss4 Score (CGS) and Molecular Weight (MW) CGS/MW and distance from cofactor (Dis) were essential for class predictions and showed TPR=0.72. Substrates consistently had lower BDE, Dis, and CGS/MW than non-substrates. Hybrid models also performed acceptablely for SOS predictions. Using the best models, Algorithms gave an acceptable performance in class prediction: TPR=0.62, False Positive Rate (FPR)=0.24, Balanced accuracy (BA)=0.69, and SOS prediction: TPR=0.98, FPR=0.60, and BA=0.69. A rule-based method was added to improve the predictive performance, which improved the algorithm TPR, FPR, and BA. Validation using an external dataset of drug-like compounds gave class prediction: TPR=0.67, FPR=0.00, and SOS prediction: TPR=0.80 and FPR=0.44 for the best Algorithm. Comparisons with standard ML models also show that our algorithm shows higher predictive performance for classification on external datasets. Overall, these models and algorithms (SOS predictor) give accurate substrate class and site (SOS) predictions for SULT-mediated Phase II metabolism and will be valuable to the drug discovery community in academia and industry. The SOS predictor is freely available for academic/non-profit research via the GitHub link.

Theoretical and experimental study of a new antioxidant xanthone: Solvent and intramolecular hydrogen bond effects

Free radicals are harmful reactive species that cause various problems in the human body. Antioxidant compounds, such as xanthones found in natural products, can help prevent these effects. This study focuses on the antioxidant behavior of ravenelin (RVL) and ravenelin B (RVLB), a newly discovered xanthone in the Exserohilum rostratum fungus. Both experimental and in silico tests were conducted, comparing them to ascorbic acid, a standard antioxidant. The results showed that RVL has a lower bond dissociation energy (312 kJ/mol) than ascorbic acid (313 kJ/mol), indicating comparable antioxidant performance. This difference is mild but agrees with the experiment that indicates RVL efficiency is equivalent to ascorbic acid at low concentrations. RVLB, however, demands higher dissociation energy (323 kJ/mol) and consequently it has a lower antioxidative efficiency. Thus, antioxidant capacity is found as RVL>ascorbic acid>RVLB. From experimental assays, the RVL performance was confirmed through experimental tests at different solute concentrations. The study also examines the effects of solvents and intramolecular hydrogen bonds. Ravenelin molecules present three hydroxyl groups involved in intramolecular OH⋯O interactions. However, analysis based on the infrared spectra, as well as Bader's theory and non-covalent interactions done in water solvent showed that the two strongest H-bonds (≈−37 kJ/mol) better stabilize the molecular structure, but are not favorable to antioxidant reactions, indicating that hydrogen scavenging occurs at the less hydrogen-bonded hydroxyl group. The solvent also plays an active role first in facilitating hydrogen abstraction besides changing the hydrogen scavenging mechanism according to the environmental polarizability. Additionally, the antioxidant mechanism of ravenelin molecules changes from nonpolar to polar solvents, allowing for hydrogen abstraction.

Catalytic Asymmetric Access to Structurally Diverse N-Alkoxy Amines via a Kinetic Resolution Strategy.

Chiral N-alkoxy amines are increasingly vital substrates in bioscience. However, asymmetric synthetic strategies for these compounds remain scarce. Catalytic kinetic resolution represents an attractive approach to prepare structurally diverse enantiopure N-alkoxy amines, which has remained elusive due to the notably reduced nucleophilicity of the nitrogen atom together with the low bond dissociation energies of labile NO-C and N-O bonds. We here report a general kinetic resolution of N-alkoxy amines through chemo- and enantioselective oxygenation. The mild and green titanium-catalyzed approach features broad substrate scope (55 examples), noteworthy functional group compatibility, high catalyst turnover number (up to 5200), excellent selectivity factor (s > 150), and scalability.

An atomistic simulation study on ductility of amorphous aluminum oxide

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 TiO2 and SiO2, underscoring the intrinsic plasticity of aluminum oxide. Furthermore, we discovered that aluminum oxides possess a low bond-dissociation energy (EBD) compared to other structural ceramic oxides, leading to a higher occurrence frequency of plastic deformation mechanisms. Based on these observations, low EBD 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.

Precise Regulation on the Bond Dissociation Energy of Exocyclic C-N Bonds in Various N-Heterocycle Electron Donors via Machine Learning.

Heterocycles with saturated N atoms (HetSNs) are widely used electron donors in organic light-emitting diode (OLED) materials. Their relatively low bond dissociation energy (BDE) of exocyclic C-N bonds has been closely related to material intrinsic stability and even device lifetime. Thus, it is imperative to realize fast prediction and precise regulation of those C-N BDEs, which demands a deep understanding of the relationship between the molecular structure and BDE. Herein, via machine learning (ML), we rapidly and accurately predicted C-N BDEs in various HetSNs and found that five-membered HetSNs (5-HetSNs) have much higher BDEs than almost all 6-HetSNs, except emerging boron-N blocks. Thorough analysis disclosed that high aromaticity is the foremost factor accounting for the high BDE of 5-HetSNs, and introducing intramolecular hydrogen-bond or electron-withdrawing moieties could also increase BDE. Importantly, the ML models performed well in various realistic OLED materials, showing great potential in characterizing material intrinsic stability for high-throughput virtual-screening and material design efforts.

Exploring a Fused Triazole-Tetrazine Binary CN Material for a Promising Initiating Substance.

The pursuit of binary carbon-nitrogen (CN) materials with high density and good thermal stability presents a significant challenge due to the inherent trade-off between high-energy storage and low bond dissociation energy. In this study, we designed and synthesized (S)-1,2-bis(3-azido-1H-1,2,4-triazol-1-yl)diazene (BAzTD) and 2,9-diazidobis([1,2,4]-triazolo)[1,5-d:5',1'-f][1,2,3,4]tetrazine (DAzTT) through a straightforward reaction. Remarkably, DAzTT demonstrated a high density of 1.816 g·cm-3 (at 298 K) and a considerable thermal decomposition temperature of 216.86 °C. These properties outperform those of previously reported binary heterocyclic CN compounds and polyazido heterocyclic compounds. The quantum-chemical methods further substantiated the integral role of aromaticity as the driving force behind this difference. Additionally, the initiation capability of DAzTT was evaluated by a notably low minimum primary charge (MPC = 40 mg), surpassing conventional organic primary explosives, such as commercial 2-diazo-4,6-dinitrophenol (DDNP, MPC = 70 mg). The exceptional priming ability highlights the potential as an environmentally friendly replacement for toxic lead azide. DAzTT sets a new standard for binary CN compounds and provides a valuable precursor for high-nitrogen carbon nitride materials.

Activation of C(SP3)–H Bonds Promoted Oxidation of Sulfides by O2 Under Catalyst-Free Conditions

Oxidation of organic sulfides is a significant reaction due to its application in many fields. Herein, we have developed a novel catalyst-free oxidation of organic sulfides by O2 under relatively mild conditions. The choice of the procedure was based on the well-acknowledged reactivity of the active C(sp3)-H bond of organic compounds to form the corresponding alkyl carbon free radicals (Rand#183;) in the presence of O2. The results showed that hydrocarbons such as tetrahydronaphthalene (THN) and cumene possessing the active C(sp3)-H bonds due to their lower bond dissociation energy (BDE), as a solvent, markedly promoted this catalyst-free sulfoxidation. It has been proved that reactive oxygen species (ROS) in this reaction are alkyl-peroxide radicals that are produced from Rand#183;, which is derived from the homolytic cleavage of the active C(sp3)-H bond with the help of heating and dioxygen, and further its activation of molecular oxygen. On this basis, combined with the DFT calculation of the activation energy of two reaction pathways, a possible reaction mechanism is proposed. The work provided a green synthesis approach of sulfoxide and sulfone compounds, and a scientific basis for a green process of ultra-deep desulfurization of fuel oils.

Experimental study of the impact of alcohols on the oxidation stability of a surrogate jet-fuel

The addition of biofuel in jet fuels can be seen as a promising answer to reduce the carbon footprint of the aviation transport sector. In this work, the impact of the addition of alcohols on the oxidation stability of a jet fuel surrogate was investigated. Different chemical structures of bioalcohols were considered and blended with n-decane used as the surrogate. The thermal oxidation stability of the mixtures was measured in a standard PetroOxy apparatus, which measures an induction period (IP). In addition to this global indicator of the fuel thermal stability, we quantified the total hydroperoxide concentration at the end of the test by iodometric titration. The influence of the length of the carbon chain in alcohols (1-butanol to 1-decanol) and the isomeric structure of butanols on the IPs of pure n-decane have been quantified. We show that the addition of a low percentage by volume of alcohols in the fuel increases its oxidation stability. This effect is non-linear, and the IP value increases with the volume percentage of alcohol in the fuel up to 10%. Beyond this value, a decrease in the stability of the mixture is observed. The influence of the length of the carbon chain is shown to be negligible. In contrast, the structure of butanol isomers strongly impacts the stabilization efficiency of the alcohol in the fuel. Conclusions on the fundamental chemical mechanism are drawn from ab initio calculations and highlight the central role of the low bond dissociation energy of the H-atoms linked to the carbon atom bearing the OH group in the liquid phase and the fate of the formed radical which ultimately yields HO2 and an aldehyde upon its reaction with O2. This mechanism is specific to linear alcohols and differs from the classic mechanism of autooxidation of alkanes.

The influence of substituents in governing the strength of the P-X bonds of substituted halophosphines R1R2P-X (X = F and Cl).

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 298K) differ by up to 117.0kJmol-1, with (H3Si)2P-F having the lowest BDE (439.5kJmol-1) and F2P-F having the largest BDE (556.5kJmol-1). In the case of the chlorophosphine-type molecules, the difference in BDEs is considerably smaller (i.e., 72.6kJmol-1), with (NC)2P-Cl having the lowest P-Cl BDE (299.8kJmol-1) and (HO)2P-Cl having the largest (372.4kJmol-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) kJmol-1.

On the mechanism of initiation steam cracking of C6 hydrocarbons by hyperbranched poly(amidoamine) (PAMAM) initiator

Initiators with low bond dissociation energy can initiate the cracking of hydrocarbons, but the initiation effect on hydrocarbons with different molecule structures remains ambiguous. In this study, the steam cracking of three C6 hydrocarbons, namely n-hexane, iso-hexane and methyl-cyclopentane (MCP), initiated by hyperbranched poly(amidoamine) (PAMAM) were investigated experimentally in a stainless-steel tubular reactor, and the detailed kinetic reaction models and reaction process simulations were conducted by Reaction Mechanism Generator and Chemkin-pro software packages. The results confirm that the addition of PAMAM can significantly promote the cracking conversion and reduce the initial cracking temperature of hydrocarbons because the decomposition of PAMAM at relatively low temperature produces high concentration of active NH2 and CH3 radicals, which significantly increases the rate of hydrogen abstraction. Importantly, the promotion efficiency of the initiator can be highly dependent on the cracking behaviour of hydrocarbons. The initiator will show higher promotion efficiency for hydrocarbon that is more prone to undergo sustained hydrogen abstraction after initiation. Therefore, the promotion efficiency of PAMAM follows the order of n-hexane > iso-hexane > MCP. This study is helpful for a better understanding of the initiation mechanism and will guide the design and screening of effective initiators for naphtha with different compositions.

Bismut in der Dynamisch Kovalenten Chemie: Makrocyclen und Siebenkernige Komplexkationen mit Ungewöhnlichen Strukturen

AbstractDynamisch kovalente Chemie (DCvC) ist ein wertvolles und breit eingesetztes Werkzeug in der modernen Synthesechemie, das auf dem reversiblen Knüpfen und Brechen kovalenter Bindungen basiert. Eine der inhärenten Stärken dieses Ansatzes ist das Potential, in einfachen Syntheseprotokollen reversibel neue Strukturmotive generieren zu können, die mit anderen Methoden nur schwer oder gar nicht zugänglich sind und eine Vielzahl von Bindungsbrüchen und ‐knüpfungen erfordern. Bislang sind diese fundamentalen synthesechemischen und konzeptionellen Herausforderungen in der DCvC verstärkt mit leichteren p‐Block‐Elementen angegangen worden, obwohl schwerere p‐Block‐Elemente angesichts geringer Bindungsdissoziationsenergien ideal geeignet für den Einsatz in der DCvC erscheinen. Wir zeigen hier, dass eine zweikernige metallorganische Bismutverbindung, bestehend aus zwei Thioxanthen‐verbrückten BiMe2‐Einheiten, bereitwillig selektive und reversible Bi−C Bindungsbrüche vollzieht, wenn sie externen Stimuli ausgesetzt wird. Das Ausnutzen von DCvC in der metallorganischen Chemie schwerer p‐block‐Elemente gewährt Zugang zu präzedenzlosen Makrocyclen und oligonuklearen Komplexen mit Fass‐ähnlicher Struktur.

Bismuth in Dynamic Covalent Chemistry: Access to a Bowl-Type Macrocycle and a Barrel-Type Heptanuclear Complex Cation.

Dynamic covalent chemistry (DCvC) is a powerful and widely applied tool in modern synthetic chemistry, which is based on the reversible cleavage and formation of covalent bonds. One of the inherent strengths of this approach is the perspective to reversibly generate novel structural motifs in an operationally simple approach, which are difficult or impossible to access with more traditional methods and require multiple bond cleaving and bond forming steps. To date, these fundamentally important synthetic and conceptual challenges in the context of DCvC have predominantly been tackled by exploiting compounds of lighter p-block elements, albeit heavier p-block elements show low bond dissociation energies and appear to be ideally suited for this approach. Here we show that a dinuclear organometallic bismuth compound, containing BiMe2 groups that are connected by a thioxanthene linker, readily undergoes selective and reversible cleavage of its Bi-C bonds upon exposure to external stimuli. The exploitation of DCvC in the field of organometallic heavy p-block chemistry grants access to unprecedented macrocyclic and barrel-type oligonuclear compounds.

Composition, nanostructure and stability of Cu-modified C-A-S-H in antibacterial alkali-activated slag

Antimicrobial alkali-activated slag (AAS) has been envisioned as a biologically resistant binder for potential application in sewer structures against biogenic sulfuric acid attacks. This work investigates the composition, phase assemblage, micro- and nano-structural alterations of AAS binders incorporating Cu-based antimicrobial agents (i.e., copper oxide and copper nitrate), as well as their antimicrobial properties and degradation mechanism under biological corrosion caused by sulphur-oxidising bacteria Acidithiobacillus thiooxidans. The results show that the incorporation of copper oxide or copper nitrate increases the degree of hydration of slag but reduces the mean chain length (MCL) of C-A-S-H as Cu preferably affects the bridging AlO4-tetrahedra over SiO4-tetrahedra. The substitution of Cu for the CaO polyhedral at the edges and corners of the C-A-S-H main chain makes the Al linkage blocked. Cu also possesses a charge-balancing role, resulting in a lower protonation of C-A-S-H in the Cu-doped AAS than that in the neat AAS, where C-A-S-H is a Tobermorite structure with MCL between 5 and 11. The Cu-doped AAS pastes show excellent antimicrobial efficiency, in particular, the CuO-doped AAS demonstrates 100 % effectiveness in inhibiting biofilm formation, with the corrosion depth significantly reduced by a factor of 10. The Cu ion is released initially from the outer surface of C-A-S-H due to its low bond dissociation energy, followed by the weak position, namely the AlO4-tetrahedra at the bridging position, rendering the rupturing of the C-A-S-H structure.

A computational investigation of pyrrole borane as a potential hydrogen storage system

A detailed theoretical analysis of the unsaturated adduct pyrrole borane and its dehydrogenated counterpart has been performed to explore its capabilities towards hydrogen storage. Thermochemical parameters at CCSD(T) and CBS-QB3 level, B-N bond dissociation energies at CCSD(T) level and the potential energy surface associated with dehydrogenation at CBS-QB3 level have been investigated. A comparative structural analysis revealed that pyrrole borane has a longer dative B-N bond distance, and consequently a lower bond dissociation energy, compared to pyrrolidine borane. The predicted enthalpies of dehydrogenation at various temperatures indicates the hydrogen elimination reaction of pyrrole borane is more exothermic and not much closer to thermoneutrality than related saturated systems. Transition state structures for the BH3-catalysed dehydrogenation reaction pathways revealed that dehydrogenation of pyrrole borane should still be favoured over dissociation and calculated rate constants at different temperatures indicates hydrogen release from pyrrole borane with BH3 catalyst can be favoured even at 298 K.

Innovative screening for functional improved aromatic amine derivatives: Toxicokinetics, free radical oxidation pathway and carcinogenic adverse outcome pathway

Aromatic amines, one of the most widely used low-cost antioxidants in rubbers, have been regarded as pollutants with human health concerns. To overcome this problem, this study developed a systematic molecular design, screening, and performance evaluation method to design functionally improved, environmentally friendly and synthesizable aromatic amine alternatives for the first time. Nine of 33 designed aromatic amine derivatives have improved antioxidant property (lower bond dissociation energy of N-H), and their environmental and bladder carcinogenicity impacts were evaluated through toxicokinetic model and molecular dynamics simulation. The environmental fate of the designed AAs-11–8, AAs-11–16, and AAs-12–2 after antioxidation (i.e., peroxyl radicals (ROO·), hydroxyl radicals (HO·), superoxide anion radicals (O2·-) and ozonation reaction) was also analyzed. Results showed that the by-products of AAs-11–8 and AAs-12–2 have less toxicity after antioxidation. In addition, human bladder carcinogenicity of the screened alternatives was also evaluated through adverse outcome pathway. The carcinogenic mechanisms were analyzed and verified through amino acid residue distribution characteristics, 3D-QSAR and 2D-QSAR models. AAs-12–2, with high antioxidation property, low environmental impacts and carcinogenicity, was screened as the optimum alternative for 3,5-Dimethylbenzenamine. This study provided theoretical support for designing environmentally friendly and functionally improved aromatic amine alternatives from toxicity evaluation and mechanism analysis.

Effect of hindered phenolic antioxidants on crosslinking characteristics of low-density polyethylene initiated by peroxide

Hindered phenolic antioxidants are the most prevalent antioxidants used in crosslinked polyethylene (XLPE) insulating materials of high-voltage (HV) cables. Doping antioxidants is conducive to delaying the low-temperature pre-crosslinking, but decreases final crosslinking degree. In order to comprehensively reveal the effect of hindered phenolic antioxidants on the crosslinking characteristics of XLPE insulating materials, four kinds of insulating materials doped with different hindered phenolic antioxidants are studied by experiment and simulation methods. The results demonstrate that antioxidant 300 is better for delaying low-temperature pre-crosslinking of insulating materials, but negative for maintaining high crosslinking efficiency and degree. Although insulating materials with antioxidant 1010 have higher crosslinking degree, it is poor to delay the low-temperature pre-crosslinking. Notably, antioxidant 245 with phenolic hydroxyl of lower bond dissociation energies can delay the low-temperature pre-crosslinking to some extent, meanwhile, crosslinking efficiency and degree of XLPE are still higher. Notably, the crosslinking characteristics of XLPE insulating materials are closely related to molecular structure of antioxidants, including functional group and ortho-substituents. Comprehensively considering the demands of delaying low-temperature pre-crosslinking and maintaining high crosslinking degree of insulating materials, antioxidant 245 is the better choice. This study provides a theoretical guidance for the choice of hindered phenolic antioxidants used for HV cable insulating materials.