Exothermic Formation Research Articles

Alternate formation of AlOH from third row diatomic hydrides and oxides

One of the most abundant Al-containing molecules detected in the interstellar medium (ISM) is AlOH. Over the past several years, there have been various pathways proposed for the formation of AlOH in the ISM, including reactions between AlO and H2 or H2O. However, these pathways include an energetic barrier from a transition state that likely prevents the reaction from progressing efficiently in the low temperature/low pressure environment of the ISM. Recently, a barrierless pathway for formation of AlOH from AlO and AlH has been proposed for the formation of AlOH. Even so, only one of these species really needs to contain an aluminum atom. To account for this, alternative but related pathways reacting the known interstellar molecule AlO with XH and AlH with XO (X = Mg, Si, P, or S) to form AlOH are explored with high accuracy quantum chemical calculations via CCSD(T)-F12b/cc-pVTZ-F12. Each third row element has at least one pair of reactants that lead to exothermic formation of AlOH. These reactions can go on to form other aluminum oxides and aluminum oxide clusters that may, in part, lead to the formation of interstellar dust grains.

On the Formation and Detectability of H2CNCN and Its Progenitors

New highly exothermic formation pathways incorporating both thermodynamic and kinetic control for the newly astronomically detected H2CNCN molecule are paired with extremely accurate quantum chemical rovibrational spectroscopic computations. The reactions between astronomically known CH2CN/CH2CCH + HNCN follow effectively identical pathways and proceed through stable intermediates and over deeply submerged transition states to form H2CNCN and HCN/HCCH coproducts. Similarly, the reaction between CH2CN and NCN− can also form H2CNCN, although this pathway first requires the initial formation of NCN−, which is currently undetected in space, via HNCN + CN−. This two-step mechanism uses the highly abundant CN− as the catalyst. Incredibly accurate quantum chemical spectroscopic data are reported for all reactants and products of these reactions, with errors between experimental values and the computations herein on the order of 0.1% or less. Anharmonic vibrational frequencies and intensities are also reported in order to guide experimental and observational searches for these molecules that have mostly been detected in the radio but may now be detectable via JWST.

Molecular dynamics study of sintering of faceted cubic boron nitride nanoparticles at high temperatures

The sintering mechanisms and temperature dependence of coalescence of colliding cubic boron nitride (c-BN) nanoparticles are investigated using classical molecular dynamics (MD) simulation. Particle-particle collisions of 2.55-nm octahedral c-BN nanoparticles, consisting solely of the most stable {111} facets, with half of the surface terminations being boron and the other half nitrogen, are analyzed statistically and evaluated to assess the initial temperature range (2500 K – 3100 K) for sintering and its effect on grain growth. At these temperatures, the collision process maximizes contact surface area through interfacial sliding, thereby minimizing free energy and accommodating dangling bonds. Moreover, the exothermic formation of bonds of the coalescing nanoparticles increases the temperature. The alignment of the {111} orientation of the two collided nanoparticles occurs at a temperature slightly above the melting point, and rapid grain growth happens when the temperature is a few hundred degrees higher than that. However, phase separation also takes place at the corners away from the collision plane of the merging nanoparticles. Between 3100 K and 3250 K, crystalline alignment occurs, which aids the sintering process and allows for the formation of a well-structured nanocluster. However, above 3300 K, phase separation dominates and drives the melting of the entire sintered nanocluster.

Single‐Atom Catalysts Based on the Mo2CO2 MXene for CO Oxidation

AbstractThrough density functional theory calculations, the mechanism of CO oxidation to CO2 on single‐atom catalysts consisting of an atom of Ti, Fe, or Zn deposited on the surface of the Mo2CO2 MXene is investigated. In the case of Fe@Mo2CO2, a mechanism resembling that of Termolecular Langmuir–Hinshelwood (TLH) is thermodynamically and kinetically favored, displaying very exothermic CO2 formation, low activation energies, and easy CO2 desorption. On Ti@Mo2CO2, the dissociation of CO2 is almost barrierless and much more likely to occur than CO2 desorption, barring the usage of this surface as a catalyst for CO oxidation. Finally, on Zn@Mo2CO2, a hybrid Langmuir–Hinshelwood/Eley–Rideal (LH/ER) mechanism is thermodynamically and kinetically feasible. Here, after the first CO2 forms, with an energy barrier of only 0.62 eV, the second CO2 is formed spontaneously, and the Zn–CO2 interactions are weak enough to allow desorption. The calculated thermodynamic quantities and reaction rates at T = 300 K indicate that Fe@Mo2CO2 should be quite active toward CO oxidation, followed by Zn@Mo2CO2, while the Ti‐based model is inactive. The results add to the evidence that establishes single transition metal atoms adsorbed on MXene surfaces as cheap and easily obtainable catalysts that offer the best of both bare and functionalized MXenes.

Synthesis, characterization and biological applications of a new nano-sized binuclear copper(II) complex containing bathophenanthroline and ellagic acid as ligands

A new binuclear copper(II) complex, nano-[Cu2-(DIP)2-EA], was synthesized by using bathophenanthroline and ellagic acid ligands in a multi-component/one-pot method, and then characterized by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectrophotometry (UV–vis), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM). The antioxidant, antibacterial, and anticancer properties of the synthesized nano-[Cu2-(DIP)2-EA] were studied. The DPPH radical test pointed out that the nano-[Cu2-(DIP)2-EA] enjoys a good potential (28.4 %) to scavenge free radicals and the bacteria culture indicated a moderate ability of the complex to prevent the growth and proliferation of gram-positive bacteria (Staphylococcus aureus ATCC 29,213) and gram-negative ones (Pseudomonas aeruginosa ATCC 27,853). The cell culture displayed a superior ability of nano-[Cu2-(DIP)2-EA] to destroy breast cancer cells (MCF-7) compared to ellagic acid. In addition, the binding interaction of nano-[Cu2-(DIP)2-EA] with ct-DNA was studied in vitro (pH 7.40) by ultraviolet-visible absorption spectrophotometry, fluorescence emission spectrofluorimetry, circular dichroism (CD) spectropolarimetry, viscosity assessment technique, and molecular docking computer simulation. The results of the fluorescence enhancement spectra clearly showed a desirable affinity of nano-[Cu2-(DIP)2-EA] to ct-DNA. A hyperchromic effect was observed along with a slight red shift in the UV-visible spectra of nano-[Cu2-(DIP)2-EA]-DNA adduct, indicating that the nano-[Cu2-(DIP)2-EA] can form a conjugate with ct-DNA molecule. Thermodynamic properties exhibited an exothermic spontaneous formation of nano-[Cu2-(DIP)2-EA]-DNA adduct favored by H-bonds and van der Waals forces. The competitive emission investigations using methylene blue (MB) and Hoechst 33,258 demonstrated that the binuclear copper(II) can replace the DNA-bound Hoechst and interact via minor grooves, as confirmed also by negligible viscosity alterations. The CD observations proposed that the nano-[Cu2-(DIP)2-EA] induces conformational changes in the ct-DNA. Molecular docking modeling results recognized a minor groove mechanism of nano-[Cu2-(DIP)2-EA] to interact with ct-DNA, and the complexation process is supported by H-bonds and van der Waals interactions.

Strain tuned structural, mechanical, electronic, and optical properties of lead-free oxy-nitride SrTaO2N perovskite using first-principles study

Recent advancements in perovskite-based solar energy conversion technologies require materials having enhanced optoelectronic properties and stability. Harnessing density functional theory (DFT), we have investigated here a novel orthorhombic phase of a recently synthesized oxynitride perovskite, SrTaO2N, and its uniaxial strain-tunable electronic and optical properties. Phonon dispersion and formation energy calculations are utilized to determine lattice dynamic stability and exothermic formation feasibility of the structure, correspondingly. The predicted bandgap at the Heyd–Scuseria–Ernzerhof [generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE)] level is ∼2.125 eV (∼1.125 eV), which is highly receptive to uniaxial strains. The bandgap formed in between X and G points with high symmetry at the first Brillouin zone was further dissected using the atomic orbital projected density of states (PDOS). The PDOS showed that the N-pz orbital dominantly contributes to valence band maxima and the Ta-dz2 orbital to conduction band minima. Compressive uniaxial strain widens the bandgap by ∼1.21 times, while tensile uniaxial strain lowers the bandgap by ∼1.1 times from the intrinsic value, suggesting strain switchable bandgap nature in the material. An elastic constant matrix also evaluates the mechanical stability of strained structures, and we found that in the strained structures from −6% to +6%, SrTaO2N is mechanically stable and ductile. Optical absorption reveals an increased absorption coefficient in the visible spectrum. These strain-tuned optoelectronic properties through the DFT approach thus suggest an evident route to a wide range of optoelectronics applications of the SrTaO2N perovskite material.

Interaction studies of water-soluble Zn(II) complex with calf thymus DNA using biophysical and molecular docking methods"

The binding between a fluorescent water-soluble Zn(II) complex of {2-[N-(2-hydroxyethylammonioethyl) imino methyl] phenol} and calf thymus DNA (ct-DNA) was investigated using spectroscopic techniques. The complex was prepared and identified by FT-IR, and 1H NMR spectroscopies. The significant changes in the absorption and the circular dichroism spectra of ct-DNA in the presence of the Zn(II) complex implied the interaction between the Zn(II) complex and ct-DNA. Upon addition of ct-DNA, the fluorescence emission intensity of the Zn(II) complex was increased and indicated the interaction between the Zn(II) complex and ct-DNA was occurred. The binding constant values (Kb) resulted from fluorescence spectra clearly showed the Zn(II) complex affinity to ct-DNA. The fluorescence studies also approved the static enhancement mechanism in the Zn(II) complex-DNA complexation process. The thermodynamic profile exhibited the exothermic and spontaneous formation of ct-DNA-Zn(II) complex system via hydrogen bonds and van der Waals forces. The competitive fluorescence investigation by methylene blue (MB), and Hoechst 33258 demonstrated that the Zn(II) complex could replace the DNA-bound Hoechst and bind to the minor groove binding site in ct-DNA. The viscosity changes were negligible, representing the Zn(II) complex binding to DNA via the groove binding mode. Molecular docking simulation affirmed that the Zn(II) complex is located in the minor groove of ct-DNA near the DG12, DA17, DA18, and DG16 nucleobases.

Resolving the Formation Mechanism of HONO via Ammonia-Promoted Photosensitized Conversion of Monomeric NO2 on Urban Glass Surfaces

Understanding the formation processes of nitrous acid (HONO) is crucial due to its role as a primary source of hydroxyl radicals (OH) in the urban atmosphere and its involvement in haze events. In this study, we propose a new pathway for HONO formation via the UVA-light-promoted photosensitized conversion of nitrogen dioxide (NO2) in the presence of ammonia (NH3) and polycyclic aromatic hydrocarbons (PAHs, common compounds in urban grime). This new mechanism differs from the traditional mechanism, as it does not require the formation of the NO2 dimer. Instead, the enhanced electronic interaction between the UVA-light excited triplet state of PAHs and NO2-H2O/NO2-NH3-H2O significantly reduces the energy barrier and facilitates the exothermic formation of HONO from monomeric NO2. Furthermore, the performed experiments confirmed our theoretical findings and revealed that the synergistic effect from light-excited PAHs and NH3 boosts the HONO formation with determined HONO fluxes of 3.6 × 1010 molecules cm-2 s-1 at 60% relative humidity (RH) higher than any previously reported HONO fluxes. Intriguingly, light-induced NO2 to HONO conversion yield on authentic urban grime in presence of NH3 is unprecedented 130% at 60% RH due to the role of NH3 acting as a hydrogen carrier, facilitating the transfer of hydrogen from H2O to NO2. These results show that NH3-assisted UVA-light-induced NO2 to HONO conversion on urban surfaces can be a dominant source of HONO in the metropolitan area.

3D-structure of intermetallic interface layer in Al–steel clad material

This paper reveals the 3D character of the intermetallic layer at the aluminum–steel interface which pops up above the original sample surface during annealing. Popping out of the intermetallics was proven using atomic force microscopy. The phase expands out of the plane due to the exothermic formation of the Al5Fe2 phase and the feasibility of surface diffusion. Milling by a focused ion beam enabled the comparison of the chemical composition of the surface layer with the bulk interface, showing no difference. The growth direction is both towards aluminum and steel — the main diffusion flux is from aluminum towards steel, and the new intermetallic phase emerges at the steel side. The shortage of Al atoms causes a shift of the intermetallic as a whole towards aluminum.

Theoretical exploration of new particle formation from glycol aldehyde in the atmosphere – A temperature-dependent study

Catalytic routes for the hydration and ammonolysis reactions of glycolaldehyde (OHCH2CHO), a bifunctional carbonyl compound in the atmosphere, is investigated employing density functional methods. Energetics of reactions catalysed by water (monomer and dimer), ammonia, and ammonia-water complex have been explored. A substantial lowering of activation energies has been noticed in all these assisted pathways compared to the unassisted mechanism. Transition state theory estimates reveal larger effective rate constants for the water-assisted pathways (for both hydration and ammonolysis) than other catalytic agents.The structural and thermodynamic properties of the molecular clusters have been investigated in the gas phase. Thermodynamic data reveals the exothermic formation of clusters. Important role of hydrogen bonding network towards stabilising the molecular clusters was noticed. This study may shed light on the underlying molecular insights on new particle formation from degradation products of glycol aldehyde under atmospheric conditions.

Formation of H3O+ and OH by CO2 and N2O trace gases in the atmospheric environment.

The impact of cosmic rays' energetic subatomic particles on climate and global warming is still controversial and under debate. Cosmic rays produce ions that can trigger fast reactions affecting chemical networks in the troposphere and stratosphere especially when a large amount of relevant trace gases such as carbon dioxide, methane, sulfur dioxide and water are injected by volcanic eruptions. This work focuses on synchrotron experiments and an ab initio theoretical study of the ion chemistry of carbon dioxide and nitrous oxide radical cations reacting with water. These molecules catalyze a fast exothermic formation of hydronium ions H3O+ and the hydroxyl radical OH, the main oxidant in the atmosphere. Moreover, theoretical calculations demonstrate that at the end of the catalytic cycle, CO2 and N2O are produced vibrationally excited and subsequently they quench in the microsecond time scale by collision with the surrounding atmospheric molecules at the pressure and temperature of the upper-troposphere/stratosphere. The chemistry involved in these reactions has a strong impact on the oxidant capacity of the atmosphere, on the sulfate aerosol production, on the cloud formation and eventually on the chemical networks controlling climate and global warming models.

DFT insights into the mechanism of O2 activation catalyzed by a structural and functional model of cysteine dioxygenase with tris(2-pyridyl)methane-based ligand architecture

Cysteine dioxygenation is an important step in the metabolism of toxic L-cysteine (Cys) in the human body, carried out by cysteine dioxygenase enzyme (CDO). The disruption of this process is found to elicit neurological health issues. This work reports a computational investigation of mechanistic aspects of this reaction, using a recently reported tris(2-pyridyl)methane-based biomimetic model complex of CDO. The computed results indicate that, the initial SO2 bond formation process is the slowest step in the S-dioxygenation process, possessing an activation barrier of 12.7 kcal/mol. The remaining steps were found to be downhill requiring very small activation energies. The transition states were found to undergo spin crossover between triplet and quintet states, while the singlet surface remained unstable throughout the entire reaction. In essence, the mechanistic scheme and multistate reactivity pattern together with the relatively small computed rate-limiting activation barrier as well as the exothermic formation energy demonstrate that the model complex is an efficient biomimetic CDO model. In addition, the study also substantiates the involvement of Fe(IV)oxido intermediates in the mechanism of S-dioxygenation by the chosen model complex. The insights derived from the O2 activation process might pave way for development of more accurate CDO model catalysts that might be capable of even more efficiently mimicking the geometric, spectroscopic and functional features of the CDO enzyme.

Stability of and conduction in single-walled Si2BN nanotubes

We explore the possibility and potential benefit of rolling a ${\mathrm{Si}}_{2}\mathrm{BN}$ sheet into single-walled nanotubes (NTs). Using density functional theory (DFT), we consider both structural stability and the impact on the nature of chemical bonding and conduction. The structure is similar to carbon NTs and hexagonal boron-nitride (hBN) NTs and we consider both armchair and zigzag ${\mathrm{Si}}_{2}\mathrm{BN}$ configurations with varying diameters. The stability of these ${\mathrm{Si}}_{2}\mathrm{BN}$ NTs is confirmed by first-principles molecular dynamics calculations, by exothermal formation, an absence of imaginary modes in the phonon spectra. Also, we find the nature of conduction varies from semiconducting over semimetallic to metallic, reflecting differences in armchair/zigzag-type structures, curvature effects, and the effect of quantum confinement. We present a detailed characterization of how these properties lead to differences in both the bonding nature and electronic structures.

A new perspective on the initial hydrogenation of TiFe0.9M0.1 (M = V, Cr, Fe, Co, Ni) alloys gained from surface oxide analyses and nucleation energetics

Despite the promise of TiFe-based alloys as low-cost solid-state hydrogen storage materials with mild operating conditions and reasonable hydrogen capacity, their initial hydrogenation process is difficult, hindering broad utilization. The effect of alloying element on the initial hydrogenation kinetics of TiFe alloys, TiFe0.9M0.1 (M = V, Cr, Fe, Co and Ni), was evaluated by analyzing changes to the passivating surface oxide layer that inhibits hydrogen permeation, as well as the ease of initial-stage hydrogen absorption into the underlying matrix. X-ray photoelectron spectroscopy and atom probe tomography revealed key variations in surface oxide compositions and thinning of the passivating oxide layer compared to pure TiFe, which suggests suppressed oxide growth by alloying-induced elemental redistribution. At the same time, density functional theory calculations predicted exothermic formation of hydride nuclei when alloying with V or Cr, as well as a reduced nucleation barrier when alloying with Co or Ni. Overall, these results are consistent with the observed experimental trend of the activation kinetics. We propose that improvements in activation kinetics of TiFe with alloying arises from the combined effect of reduced passivating oxide thickness and easier hydride nucleation, offering a starting point for alloy design strategies towards further improvement.

Quantum Chemical Study on Interstellar Synthesis of Cytosine by the Automated Reaction Path Search

Novel reaction pathways with the neutral radical–molecule reaction to form cytosine, a nucleobase of DNA and RNA, which can proceed in the interstellar environment, were discovered by automated reaction pathway calculations based on the transition state theory. We suggested the barrierless and exothermic formation of cytosine in two steps. First, the reaction between the O radical and ethynamine forms a key precursor species, NH2CCHO. Then, this radical reacts with CN and HNCH to form cytosine. This study would contribute to elucidating possible reactions on nucleobases under lower temperatures, and further tests are effective by astronomical modeling/observations and laboratory experiments.

First-principles investigation of CuO decomposition and its transformation into Cu2O

This paper reports on the mechanisms of CuO decomposition and its associated phase transformation into ${\mathrm{Cu}}_{2}\mathrm{O}$, as a fundamental step of thermite materials reaction, where CuO serves as the oxidizer. The Frenkel pair defects in perfect bulk CuO show extremely high formation energy (>4 eV) indicating that its decomposition initiates at defects/interfaces/surfaces, the latter being sensitive to surface orientation. In contrast to a variety of CuO surfaces [(111), (110), ($10\overline{1}$)] exhibiting three-fold coordinated oxygen atoms, results show that oxygen vacancy formation requires higher disordered surfaces, such as the CuO(001), on which the vacancy formation activation energy is reduced to 1.31 eV. This leads to the exothermic formation of a chemisorbed O-O peroxy-bridge complex at the surface (\ensuremath{-}1.25 eV adsorption) that thermodynamically moderates the backreaction (vacancy annihilation). Further desorption of molecular oxygen necessitates an activation of 1.53 eV, compatible with CuO decomposition observed experimentally at 600 K (\ensuremath{\sim}second process duration). As a driving mechanism of oxygen release upon decomposition, migrations of the vacancy close to the surface and towards the bulk are determined for a number of crystalline directions and surface orientations and show considerable anisotropy, with two preferential directions: [110] and [001] with 1.35 and 1.77 eV activation, lowered to 1.08 and 1.03 eV activation when approaching the (111) and (001) surfaces, respectively. Finally, the CuO to ${\mathrm{Cu}}_{2}\mathrm{O}$ phase transformation follows a two-step process: a first structural modification from monoclinic to orthorhombic takes place when CuO has lost 12.5% of its oxygen atoms, followed by a barrierless transition to the cubic phase when 44--48% of the oxygen atoms have been removed, i.e., very close to stoichiometric ${\mathrm{Cu}}_{2}\mathrm{O}$.

Ab initio study of the structural stability and Dirac fermion behaviour in A3B (A = Cr, Mo, W; B = Al, Ga, In, Si, Ge, Sn, Be) and W3M, M = Ru, Ta, Re, Os, Ir, Au compounds

We study the structural stability and electronic properties of A3B (A = Cr, Mo, and W; B = Al, Ga, In, Si, Ge, Sn, and Be) compounds using ab initio pseudopotential method with Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) for the exchange-correlation functional. It is found that Cr3Be, Cr3Al, Cr3Ga, Cr3Si, Cr3Ge, Mo3Be, Mo3Al, Mo3Ga, Mo3Si, Mo3Ge, and W3Al compounds favor the A15 phase with an exothermic formation energy. In some other cases, the A15 phase has the lowest energy, but the formation energy is endothermic. The stability of these compounds remains unaffected after considering spin-orbit coupling. The charge transfer, electronic density of states, and band structure in each case have been analyzed. The Bader charge analysis shows a large variation in the electronic charge on A atoms. Further we have studied the stability of A15 phase of W3M compounds with M, a transition metal such as Ru, Ta, Re, Os, Ir, and also Au, some of which have recently attracted attention for spintronics applications. A comparison of the results and the occurrence of Dirac fermion behavior in β-W as well as the effects due to the compound formation and spin-orbit coupling have been discussed.

Thermoelectric properties and thermal stability of ferromagnetic half metallic CoVTe alloy, first principles study

ABSTRACT Thermoelectric properties and the thermal stability of ternary half-Heusler compound CoVTe are investigated for the first time, using the first principles computations. It is found that CoVTe alloy is an indirect half metallic ferromagnetic alloy. The integral value of the total magnetic moment obeys the Slater-Pauling rule which is in accordance with the half-metallic nature of this compound. The negative value of the formation energy EF and the positive value of the cohesive energy Ec show that this alloy can be easily produced experimentally with exothermic formation processes. The thermoelectric properties are computed at different temperatures from 0 to 900 K by step of 50 K and at different chemical potential values from −2 to 2 eV. Moreover, the lattice dynamical results regarding the phonon dispersion curves and phonon density of states are obtained and discussed. The investigated thermodynamic properties are in line with the results obtained by the Debye theory applied to several materials. The attractive magnetic half metallicity as well as the interesting thermoelectric properties make this alloy a good candidate for spintronic and thermoelectric applications.

Exothermic Formation Reactions as Local Heat Sources

This review focuses on the properties of reactive materials (RMs) that enable exothermic formation reactions and their application as local heat sources. We examine how the heat produced by these formation reactions can enable a range of useful functions including bonding, sealing, ignition, signaling, and built-in degradation. We begin by describing the chemistries, geometries, microstructures, and fabrication of RMs. We then explore the magnitude and measurement of their stored chemical energies and the rates and mechanisms by which the stored energy can be released to generate useful heat. The majority of the review focuses on how the released heat can be modeled and used to perform a range of functions.

CO2 trapping of selected N‐heterocyclic vinylidenes with an NBO mechanistic scrutiny by DFT

AbstractTrapping of CO2 is probed by a set of three N‐heterocyclic vinylidene minima, from the azole family, including imidazole (1), 1,2,4‐triazole (2), and tetrazole (3), at M06‐2X/6‐311++G** level of theory. Exothermic adsorption of CO2 over 1, 2, and 3 gives the initial CO2‐complex, 1a, 2a, and 3a, with no transition state (TS). Consequently, carbenic π‐additions to CO2 (within 1a, 2a, and 3a) may give reactant‐like, three‐membered cyclic TSs, which lead to the exothermic formation of 1b > 2b > 3b. Alternatively, CO2 intramolecular reactions within 1a, 2a, and 3a may result in the formation of the product‐like, five‐membered cyclic TSs, which lead to the endothermic formation of unstable side products 1c, 2c, and 3c, which revert to 1a, 2a, and 3a, respectively. Hence, this manuscript focuses on the main CO2 trapped products (1b, 2b, and 3b), and takes advantage of the immense potential of the NBO and AIM data in elucidating their formation provisional mechanisms. Unprecedentedly, contributions of different donor‐acceptor interacting orbitals to the formation of each product are assessed on the basis of their second‐order perturbation stabilization energy (E2) values.