Value Of Dissociation Energy Research Articles

Mechanism of Formation and Decomposition of C6H5(O2•)C(OH)C6H4OH

AbstractIn the present theoretical study, the thermochemical properties of Ph(O2•)C(OH)PhOH and considered products of its oxidation are calculated using the DFT approaches (M062X, B3LYP, wB97XD, M08HX, MN15) at the 6−311++G(d, p) level of theory. The DFT values of ΔraHo(Yi) of the atomization of considered structures are corrected using the linear calibration dependencies reported for the peroxides as well as for the hydrocarbons (including aromatic and simple oxygenated compounds). The values of ΔfHo(Yi, CORR) ± 3SDi, derived from the corrected values of ΔraHo(Yi, CORR), are coordinated by the intersection of their 3SDi intervals, determined previously. The values of ΔfHo(Y, MEAN) ± 2SDY of the Ph(O2•)C(OH)PhOH (2F), Ph•─OO─C(OH)PhOH (3G), HOPh•─OO─C(OH)Ph (2G), PhC(OH)2PhOH (1H), Ph(O2H)C(OH)PhOH (4G) and Ph(O•)C(OH)PhOH (1G) (corresponded, respectively, to −159.4 ± 6,−55.2 ± 6,−61.5 ± 3.7,−385.8 ± 6,−293.4 ± 1.4,−148.9 ± 6 kJ/mol), as well as the values of Ea‡ = 127.8 ± 7, 121.2 ± 8, 17.2 ± 5, 19.4 ± 3 kJ/mol, determined, respectively, for the reactions (R21a), (R21b), (R22a), (R22b) and the values of the rate constants of associated reactions, are reported for the first time. According to calculations, the replacement of >C•H by OH group increases the values of dissociation energy (DE) of >C(X)─O2•, >C(X)O─O•, >C(X)O─H, PhC(X)OO─•PhOH, and HOPhC(X)OO─•Ph bonds, but decreases those values of >C(X)O2–H, HOPhC(X)OO•Ph, and PhC(X)OO•PhOH bonds. As a result of increased stability of the >C(X)─O2• bond (X = OH), the higher temperatures can be used for the chain production of p‐PhC(O2H)HPhOH and p‐PhC(O2H)(OH)PhOH at high concentrations of p‐PhCH2PhOH. On the contrary, the contribution of reactions (R21a) and (R21b) to the oxidation is significant under low concentrations of p‐PhCH2PhOH. Its also found that the stable intermediate O2 π–π cluster, predicted for the >C•(H) radical, is not observed for the reaction of >C•(OH) with O2, due to the formation of a hydrogen bond between the OH group and partially charged O2δ−.

Theoretical Investigation of Bond Dissociation Energies of exo-Polyhedral B–H and B–F Bonds of closo-Borate Anions [BnHn−1X]2− (n = 6, 10, 12; X = H, F)

This paper reports on a theoretical investigation of the bond dissociation energies of B–H and B–F interactions of closo-borate anions [BnHn−1X]2− (n = 6, 10 and 12; X = H and F), in which homolytic and heterolytic bond breaking cases were considered, and the main trends in bond dissociation energy values were analysed. The wB97X-D3/TZVPP level of theory was applied for geometry optimisation of the molecular species under consideration. DLPNO-CCSDT/CBS single-point calculations were made to ensure an accurate estimation of the target systems’ electronic energy. The correlations between the value of the bond dissociation energy and variables such as electron density descriptors of B–H and B–F interactions and frontier orbital energies (HOMO, SOMO and LUMO) were established.

Molecular design and theoretical investigation of TNI based materials

Molecular design and theoretical investigation of TNI based materials

Bond dissociation energy of O2 measured by fully state-to-state resolved threshold fragment yield spectra.

We have determined the bond dissociation energy of O2 by measuring fully state-to-state resolved threshold fragment yield spectra in the XUV energy region, O2X3Σg-,N″,J″→O(PJ3)+O(S1o3)/O(S2o5). Our results have yielded a bond dissociation energy value of 41 269.19 ± 0.10cm-1, which is consistent with previous measurements but exhibits a significantly lower uncertainty, approximately five times smaller. It is noteworthy that this study is the first to simultaneously achieve fine structure state resolution for the parent O2molecule and spin-orbit state resolution for the O(3PJ) fragments in the measurement of O2 bond dissociation energy. As a result, our findings have established a solid foundation for the obtained data.

Superalkalis with Hydrogen as Central Electronegative Atom and their Possible Applications: Ab Initio and DFT Study.

Superalkalis are unusual species having ionization energies lower than that of the alkali metals. These species with various applications are of great importance in chemistry due to their low ionization energies and strong reducing property. A typical superalkali contains a central electronegative core decorated with excess metal ligands. In the quest for novel superalkalis, we have designed the superalkalis HLi2, HLiNa and HNa2 using hydrogen as central electronegative atom for the first time employing high level ab initio (CCSD(T), MP2) and density functional theory (ωB97X-D) methods. The superalkalis exhibit very low ionization energies, even lower than that of cesium. Stability of these species is verified from binding energy and dissociation energy values. The superalkalis are capable of reducing SO2, NO, CO2, CO and N2 molecules by forming stable ionic complexes and therefore can be used as catalysts for the reduction or activation of systems possessing very low electron affinities. The superalkalis form stable supersalts with tailored properties when interact with a superhalogen. They also show remarkably high non-linear optical responses, hence could have industrial applications. It is hoped that this work will enrich the superalkali family and spur further theoretical and experimental research in this direction.

Photocatalytic Generation of H2O2 Via a Hydrogen-Abstraction Pathway by Bi2.15WO6 under Visible Light.

Photocatalytic technology is a popular research area for converting solar energy into environmentally friendly chemicals and is considered the greenest approach for producing H2O2. However, the corresponding reactive oxygen species (ROS) and pathway involved in the photocatalytic generation of H2O2 by the Bi2.15WO6-glucose system are still not clear. Quenching experiments have established that neither •OH nor h+ contribute to the formation of H2O2, and show that the formed surface superoxo (≡Bi-OO•) and peroxo (≡Bi-OOH) species are the predominant ROS in H2O2 generation. In addition, various characterizations indicate the enhanced electron-transfer on the surface of Bi2.15WO6 with increasing contents of glucose via the ligand-to-metal charge transfer pathway, confirming H-transfer from glucose to ≡Bi-OO• or ≡Bi-OOH. The increased production of H2O2 with decreasing bond dissociation energy (BDEO-H) values of various phenolic compounds again supports the H-transfer mechanism from phenolic compounds to ≡Bi-OO• and then to ≡Bi-OOH. DFT calculations further reveal that on the Bi2.15WO6 surface, oxygen is sequentially reduced to ≡Bi-OO• and ≡Bi-OOH, while H-transfer from H2O or glucose to ≡Bi-OO• and ≡Bi-OOH, resulting in the production of H2O2. The lower energy barrier of H-transfer from adsorbed glucose (0.636 eV) than that from H2O (1.157 eV) indicates that H-transfer is more favorable from adsorbed glucose. This work gives new insight into the photocatalytic generation of H2O2 by Bi2.15WO6 in the presence of glucose/phenolic compounds via the H-abstraction pathway.

Design of N-N ylide bond-based high energy density materials: a theoretical survey.

The generally encountered contradiction between large energy content and stability poses great difficulty in designing nitrogen-rich high-energy-density materials. Although N-N ylide bonds have been classified as the fourth type of homonuclear N-N bonds (besides >N-N<, -N[double bond, length as m-dash]N-, and N[triple bond, length as m-dash]N), accessible energetic molecules with N-N ylide bonds have rarely been explored. In this study, 225 molecules with six types of novel structures containing N-N ylide bonds were designed using density functional theory and CBS-QB3 methods. To guide future synthesis, the effects of substitution on the thermal stability, detonation velocity, and detonation pressure of the structures were evaluated under the premise that the N-N ylide skeleton remains stable. The calculations show that the bond dissociation energy values of the N-N ylide bonds of the designed 225 structures were in the range of 61.21-437.52 kJ mol-1, except for N-1NNH2. Many of the designed structures with N-N ylide bonds exhibit high detonation properties, which are superior to those of traditional energetic compounds. This study convincingly demonstrates the feasibility of the design strategy of introducing an N-N ylide bond to develop new types of energetic materials.

EVALUASI SENYAWA BIOAKTIF Nasturtium montanum Wall. SEBAGAI KANDIDAT AGEN ANTIPIRETIK TERHADAP RESEPTOR PROSTAGLANDIN SYNTASE 2 (PTGS2) SECARA IN SILICO [Evaluation of Bioactive Compounds of Nasturtium montanum Wall. as Antipyretic Agent Candidate Toward Prostaglandin Syntase 2 (PTGS2) Through in Silico

The inhibition of prostaglandin syntase 2 ( PTGS2 route is necessary in order to prevent an feverfever. Antipyretic drugs such as the Non steroids ( NSAIDs are fever medication which acts as non-selective inhibitor of PTGS2. NSAID overdose cases have led to herbal ingredients utilization as alternative remedies, such as the Nasturtium montanum leaves. This research aimed to observe the interaction of selected bioactive compounds within N. montanum with the PTGS2 target protein through molecular docking. In addition, this research used in silico approach conducted with molecular docking method trough several stages such as preparation of 3D ligand structure and protein, protein sterilization by PyMOL, docking compounds with PyRx and visualization of docking results via LigPlot+. Results obtained from this research shows the bond dissociation energy value of 1-O-sinapoyl-beta-D-glucose, kaempferol 3-O-sophoroside, patuletin 3-gentiobioside and quercetin 3-O-malonylglucoside substances are smaller compared to meclofenamic acid causing the four ligand tests more stable in their binding to PTGS2 receptor. Meclofenamic acid and 1-O-sinapoyl-beta-D-glucose both bind to PTGS2 receptor with the same amino acid residue as well as the same interaction. Whereas meclofenamic acid, kaempferol 3-O-sophoroside, patuletin 3-gentiobioside and quercetin 3-O-malonylglucoside bind to PTGS2 receptor with the same amino acid residue yet have different bond interaction.

Photoinduced One‐Electron Oxidation of Estrone Derivatives: A Combined Steady‐State and Time‐Resolved Spectroscopy Investigation

AbstractA detailed investigation of the photophysics and of the redox properties of a set of selected estrone carboxylate and sulfonate esters was carried out by means of steady‐state and time‐resolved spectroscopies. The observed dual fluorescence was assigned to an efficient intramolecular energy transfer from the aromatic moiety to the carbonyl group. On the other hand, the photoinduced monoelectronic oxidation of R−OX in the presence of persulphate anion is followed by mesolytic fragmentation of the so generated radical cation into the corresponding phenoxyl radical with rate constant values (kfrag) of 104–105 s−1, that depend on the X−O bond dissociation energy values.

Modulating the electronic structure of PtFe alloys supported on carbon onions for enhancing pH-universal hydrogen evolution reaction

Modulating the electronic structure of PtFe alloys supported on carbon onions for enhancing pH-universal hydrogen evolution reaction

Selective Nsp2 - and Csp2 - Photografting of Au-Surface by Aryldiazonium Salts and Arylazo Sulfonates.

Arylazo sulfonates (Ar-N=N-SO3 Na) have been found to undergo photografting on gold surface through both Au-Nsp2 - and Au-Csp2 - bond formation. The functionalized materials have been fully characterized by infrared reflection absorption spectroscopy (IRRAS), Raman, XPS, DFT calculations and UV-Vis absorption spectroscopy. These methods permit to evidence aromatic substituents (IRRAS), the Au-N=N signature (Raman and XPS spectroscopy), and the bond dissociation energy values of the two linkages (DFT calculation). The grafting proceeds through two competitive paths, namely a stepwise reaction involving an aryl radical (for the formation of the Au-Ar bonds) and a concerted reaction on the surface of gold (for Au-N=N-Ar bond formation). The occurrence of an aryl radical upon irradiation has been fully evidenced by EPR spectroscopy. Finally, E/Z photoisomerisation of the N=N bonds present on prepared few layer films has been observed by means of UV-Vis absorption spectroscopy.

Antioxidant potential of styrene pyrone polyphenols from Inonotus obliquus: A combined experimental, density functional theory (DFT) approach and molecular dynamic (MD) simulation

Antioxidant potential of styrene pyrone polyphenols from Inonotus obliquus: A combined experimental, density functional theory (DFT) approach and molecular dynamic (MD) simulation

Extraction of scutched flax tow (SFT) in NHPI and PAG assisted H2O2 system in less water and low temperature environment

The extraction of flax fiber always consumed large amount of water and energy, and caused heavy Chemical oxygen demand (COD) discharge. Driven by the concept of green chemical and sustainable engineering, extracting flax fiber under less water environment and room temperature was necessary. This study conducted SFT degumming in nitroxide and H2O2 activating reagent aided alkali H2O2 (NAAH) system in less water environment under room temperature successfully. Results showed that N-Hydroxyphthalimide (NHPI) got much higher promoting effect in NAAH than that of 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO) due to its high bond dissociation energy value. HAR could brought up the selectivity of the NAAH system, and the promoting effect increased in the order of TAED > MA >AGC >PAG. With the assistance of PAG and NHPI, the degumming could be conducted under less water environment under room temperature. Under the optimal reaction condition (0.25 g/L NHPI, 2.5 g/L PAG, bath ratio 1:10, 30 °C, 2 h), the cellulose, hemicellulose and lignin content reached 82.19%, 10.82% and 1.74% respectively; the density, tenacity, DP value and whiteness reached 14 dtex, 78 cN/dtex, 2100 and 52.0 respectively. Compared with fiber prepared in NaOH degumming and alkali H2O2 degumming system, the fiber prepared in NAAH system get better tensile property; consumed 50% and 50% less water; 6.45 × 106 kcal/h and 5.16 × 106 kcal/h less energy, and produced 9.52% and 73.5% lower COD discharge, respectively.

Near-thermo-neutral electron recombination of titanium oxide ions.

While the dissociative recombination (DR) of ground-state molecular ions with low-energy free electrons is generally known to be exothermic, it has been predicted to be endothermic for a class of transition-metal oxide ions. To understand this unusual case, the electron recombination of titanium oxide ions (TiO+) with electrons has been experimentally investigated using the Cryogenic Storage Ring. In its low radiation field, the TiO+ ions relax internally to low rotational excitation (≲100 K). Under controlled collision energies down to ∼2 meV within the merged electron and ion beam configuration, fragment imaging has been applied to determine the kinetic energy released to Ti and O neutral reaction products. Detailed analysis of the fragment imaging data considering the reactant and product excitation channels reveals an endothermicity for the TiO+ dissociative electron recombination of (+4 ± 10) meV. This result improves the accuracy of the energy balance by a factor of 7 compared to that found indirectly from hitherto known molecular properties. Conversely, the present endothermicity yields improved dissociation energy values for D0(TiO) = (6.824 ± 0.010)eV and D0(TiO+) = (6.832 ± 0.010)eV. All thermochemistry values were compared to new coupled-cluster calculations and found to be in good agreement. Moreover, absolute rate coefficients for the electron recombination of rotationally relaxed ions have been measured, yielding an upper limit of 1 × 10-7 cm3 s-1 for typical conditions of cold astrophysical media. Strong variation of the DR rate with the TiO+ internal excitation is predicted. Furthermore, potential energy curves for TiO+ and TiO have been calculated using a multi-reference configuration interaction method to constrain quantum-dynamical paths driving the observed TiO+ electron recombination.

Inorganic Acids, Fluoridated Ethanol’s, and Some Fluoridated Saturated Hydrocarbons’ Stability and Bond Dissociation Energy Values.

The energetics of chemical processes can be assessed using bond dissociation energy values. The objective of this work is to calculate the hydrogen-halogen (H-X) and carbon- fluorine (C-F) bond dissociation energy values for some energetic materials including fluorinated ethanols, some fluorinated saturated hydrocarbons, and some inorganic acids. Bond dissociation energy values for 40 different compounds are reported in this work. All calculated bond dissociation energy is reported for standard conditions, 1 atm pressure and 298 K temperature. Bond dissociation energy values are listed in tables 1,2 and 3.

Electrostatic interactions, binding energies and structures of the [formula omitted] complexes

The binding energies and structures of the Be cations with H2 molecules are studied theoretically at the level of the MP2 method. In this study the aug-cc-pVTZ basis set is used to describe the electronic configuration of these atoms in the complex. The structures of these complexes are determined for Be+2∙H21-4 complexes. The sequential bond energies of the Be2+∙(H2)1−4 complexes are also examined. The variations in the electrostatic interaction energies could be the cause of the observed trend in sequential bond dissociation energy values.

Evaluation of Free Radical Quenching Ability of Quinoline Acids through in vitro and Theoretical Studies

Drugs based antioxidants are commonly suggested as targets while designing new medicines. All sorts of pharmaceutical drug development benefit from the extremely desirable quinoline moiety with antioxidant. In this work, the scavenging behaviour of four quinoline derivatives (Q1-Q4) towards DPPH, H2O2, ABTS and superoxide activity were investigated. According to the in vitro inhibition concentration (IC50), quinoline derivative Q1 showed high antioxidant potential. Additionally, the theoretical DFT gas phase calculations of HOMO-LUMO, MEP, NPA and NBO are used to study the conjugating systems in radicals and showed that the N-H site acts more favourable than the O-H site for the radical attack. The calculated bond dissociation energy (BDE) values demonstrated that compound Q1 follows the HAT mechanism and while the calculated ionization potential (IP) and proton dissociation energy (PDE) values showed that Q4 follows the SET-PT route. The results of these two mechanisms demonstrated that radical quenching activity occurs at the N-H and O-H sites. The spin density demonstrates that both radicals are delocalized uniformly across the molecule.

Thermodynamic Evaluation on Alkoxyamines of TEMPO Derivatives, Stable Alkoxyamines or Potential Radical Donors?

AbstractIn 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.

On the specific heat and mass loss of thermochemical transition

Poly(vinyl alcohol) PVA is a synthetic polymer used in a variety of applications and exhibits unusual thermal behavior. In this work, differential scanning calorimetry (DSC), isothermal and non-isothermal thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), optical microscopy, viscometry and kinetic modelling were used to study the thermal behavior of PVA for providing further insights about the thermochemical transition. It is shown that the value of specific heat of thermochemical transition is comparable to theoretical values derived from chemical bond dissociation energy values. Activation energy's contribution to the specific heat of thermochemical transition seems to be low. Contradictions among the conclusions from various analytical techniques, regarding the glass transition of PVA, are discussed and interpreted. Settlement of these contradictions leads to the conclusion that like PVA's melting point, its glass transition is also a thermochemical transition but with no detectable mass loss.

On the Coexistence of the Carbene⋯H-D Hydrogen Bond and Other Accompanying Interactions in Forty Dimers of N-Heterocyclic-Carbenes (I, IMe2, IiPr2, ItBu2, IMes2, IDipp2, IAd2; I = imidazol-2-ylidene) and Some Fundamental Proton Donors (HF, HCN, H2O, MeOH, NH3).

The subject of research is forty dimers formed by imidazol-2-ylidene (I) or its derivative (IR) obtained by replacing the hydrogen atoms in both N-H bonds with larger important and popular substituents of increasing complexity (methyl = Me, iso-propyl = Pr, tert-butyl = Bu, phenyl = Ph, mesityl = Mes, 2,6-diisopropylphenyl = Dipp, 1-adamantyl = Ad) and fundamental proton donor (HD) molecules (HF, HCN, HO, MeOH, NH). While the main goal is to characterize the generally dominant C⋯H-D hydrogen bond engaging a carbene carbon atom, an equally important issue is the often omitted analysis of the role of accompanying secondary interactions. Despite the often completely different binding possibilities of the considered carbenes, and especially HD molecules, several general trends are found. Namely, for a given carbene, the dissociation energy values of the IRHD dimers increase in the following order: NH< HO < HCN ≤ MeOH ≪ HF. Importantly, it is found that, for a given HD molecule, IDipp forms the strongest dimers. This is attributed to the multiplicity of various interactions accompanying the dominant C⋯H-D hydrogen bond. It is shown that substitution of hydrogen atoms in both N-H bonds of the imidazol-2-ylidene molecule by the investigated groups leads to stronger dimers with HF, HCN, HO or MeOH. The presented results should contribute to increasing the knowledge about the carbene chemistry and the role of intermolecular interactions, including secondary ones.