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Heterolysis (chemistry)
Heterolysis (chemistry)
Heterolysis (chemistry)
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In chemistry, heterolysis or heterolytic fission (from Greek ἕτερος (heteros) 'different' and λύσις (lusis) 'loosening') is the process of cleaving/breaking a covalent bond where one previously bonded species takes both original bonding electrons from the other species.[1] During heterolytic bond cleavage of a neutral molecule, a cation and an anion will be generated. Most commonly the more electronegative atom keeps the pair of electrons becoming anionic while the more electropositive atom becomes cationic.

Heterolytic fission almost always happens to single bonds; the process usually produces two fragment species.

The energy required to break the bond is called the heterolytic bond dissociation energy, which is similar (but not equivalent) to homolytic bond dissociation energy commonly used to represent the energy value of a bond.

One example of the differences in the energies is the energy required to break a H−H bond

ΔH = 104 kcal/mol
ΔH = 66 kcal/mol (in water)[2]

History

[edit]

The discovery and categorization of heterolytic bond fission was clearly dependent on the discovery and categorization of the chemical bond.

In 1916, chemist Gilbert N. Lewis developed the concept of the electron-pair bond, in which two atoms share one to six electrons, thus forming the single electron bond, a single bond, a double bond, or a triple bond.[3] This became the model for a covalent bond.

In 1932 Linus Pauling first proposed the concept of electronegativity, which also introduced the idea that electrons in a covalent bond may not be shared evenly between the bonded atoms.[4]

However, the ions had been studied before bonds mainly by Svante Arrhenius in his 1884 dissertation. Arrhenius pioneered development of ionic theory and proposed definitions for acids as molecules that produced hydrogen ions, and bases as molecules that produced hydroxide ions.

Solvation effects

[edit]

The rate of reaction for many reactions involving unimolecular heterolysis depends heavily on rate of ionization of the covalent bond. The limiting reaction step is generally the formation of ion pairs. One group in Ukraine did an in-depth study on the role of nucleophilic solvation and its effect on the mechanism of bond heterolysis. They found that the rate of heterolysis depends strongly on the nature of the solvent.

For example, a change of reaction medium from hexane to water increases the rate of tert-Butyl chloride (t-BuCl) heterolysis by 14 orders of magnitude.[5] This is caused by very strong solvation of the transition state. The main factors that affect heterolysis rates are mainly the solvent's polarity and electrophilic as well as its ionizing power. The polarizability, nucleophilicity and cohesion of the solvent had a much weaker effect on heterolysis.[5]

However, there is some debate on effects of the nucleophilicity of the solvent, some papers claim it has no effect,[6] while some papers claim that more nucleophilic solvents decrease the reaction rate.[7]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Heterolysis (chemistry)

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In chemistry, heterolysis, also known as heterolytic cleavage or heterolytic fission, is the process by which a breaks such that both s of the shared pair are retained by one of the two bonded atoms, resulting in the formation of two oppositely charged , typically a cation and an anion. This unequal distribution of electrons distinguishes heterolysis from homolysis, where the bonding pair splits evenly, with each atom receiving one electron to form neutral radicals. Heterolysis is a fundamental step in many ionic reaction mechanisms in , often occurring in polar solvents that stabilize the charged intermediates produced. The process is commonly represented using curved arrows with double barbs to indicate the movement of the from the bond to one fragment, emphasizing its role in generating reactive species such as or carbanions. For instance, in the , heterolysis of the carbon- bond in an alkyl produces a intermediate and a anion, with the departing with the . Similarly, in E1 elimination reactions, heterolysis forms a that subsequently loses a proton to yield an . These mechanisms highlight heterolysis's importance in facilitating nucleophilic and electrophilic processes, which are central to synthetic organic transformations and biochemical pathways.

Fundamentals

Definition

In chemistry, a covalent bond forms when two atoms share one or more pairs of valence electrons, resulting in a mutual attraction between the positively charged nuclei and the negatively charged between them. This sharing creates a stable linkage, with the occupying a region of high density that holds the atoms together at a characteristic internuclear distance. Heterolysis, also known as heterolytic cleavage or fission, is the process by which a covalent bond breaks such that both electrons from the shared pair are retained by one of the two bonded atoms. This unequal division produces oppositely charged species: a cation and an anion, such as a carbocation and carbanion in organic chemistry contexts. The heterolytic nature arises from the inherent polarity in many covalent bonds, where electron distribution is uneven due to differences in atomic properties, favoring the transfer of the entire electron pair to one fragment. For a generic between atoms A and B, heterolysis is represented as A—B → A⁺ + B⁻ (or A⁻ + B⁺), with the direction determined by which atom is more electronegative and thus more likely to attract and retain the . This contrasts with symmetric bond breaking, in which the shared electrons are equally divided, but heterolysis emphasizes the production of ions through this asymmetric electron assignment.

Bond Cleavage Characteristics

In heterolytic bond cleavage, the shared pair of electrons in a covalent bond is unequally distributed such that both electrons are retained by one of the bonded atoms, resulting in the formation of two oppositely charged species: an electron-deficient cation and an electron-rich anion. This process contrasts with equal sharing in homolysis and typically occurs in polar bonds where the electron pair moves entirely to one fragment. The direction of electron assignment during heterolysis is primarily governed by the relative electronegativities of the atoms involved, with the more electronegative atom acquiring both electrons to form the anion, while the less electronegative atom becomes the cation. For instance, in carbon- bonds (C—X, where X is a ), the , being more electronegative than carbon, typically takes the , yielding a and a anion. This electronegativity-driven polarization facilitates the cleavage and determines the identity of the charged fragments. The process is conventionally represented as A—B → A⁺ + :B⁻, where the colon denotes the on the anion, illustrating the complete transfer of the bonding s. To depict the electron movement, curved notation is employed in mechanistic diagrams: a double-barbed (full-headed) curved originates from the bonding and points toward the atom that will bear the negative charge, signifying the flow of the during bond rupture. This -pushing formalism provides a visual tool for tracking electron reorganization, emphasizing that the electrons are not split but relocated as a unit to the more stable site. As an immediate outcome, heterolysis generates highly reactive ionic intermediates, such as s or carbanions, whose stability depends on the atomic composition of the fragments. For example, a positive charge on a carbon atom () is destabilized relative to one on a more electropositive element, while negative charges are more stable on highly electronegative atoms like or oxygen. These intermediates are prone to further reactions due to their electron imbalance, driving subsequent chemical transformations.

Heterolysis versus Homolysis

Homolysis refers to the cleavage of a in which the shared pair of electrons is divided equally between the two resulting fragments, producing two neutral species each with an , known as free radicals./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) This process can be represented as A−B→A∙+B∙A-B \rightarrow A^\bullet + B^\bullet, where each atom retains one from the bond./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) In contrast, heterolysis involves the unequal division of the bonding electrons, with one fragment taking both electrons to form ions: a cation and an anion./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) This polar process generates charged , whereas homolysis is non-polar and yields uncharged radicals./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) Heterolysis is typically favored in polar or ionizing solvents that stabilize the resulting ions through , while homolysis predominates in non-polar environments, the gas phase, or under conditions like high or that promote radical formation without charge separation./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) The following table summarizes key differences between the two processes:
AspectHeterolysisHomolysis
Electron FateBoth electrons go to one fragmentOne electron to each fragment
Products FormedCation and anion (ions)Two radicals (neutral, unpaired s)
Typical ConditionsPolar solvents, solution phaseNon-polar solvents, gas phase, /
For instance, heterolysis occurs in SN1 reactions, where a departs with the electron pair to form a intermediate, while homolysis is central to , such as chlorination of alkanes initiated by light to generate radicals./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage) These distinctions profoundly influence reaction pathways: heterolysis leads to ionic mechanisms involving nucleophilic or electrophilic attacks, often proceeding stepwise with charge-stabilized intermediates, whereas homolysis initiates radical chain reactions characterized by initiation, propagation, and termination steps, enabling selective but highly reactive transformations./09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage)

Relation to Ionization and Dissociation

Heterolysis serves as a fundamental mechanism for in chemical systems, particularly in molecules where covalent bonds cleave asymmetrically to produce charged . In this , the shared pair of electrons from the bond is retained entirely by one fragment, resulting in the formation of a cation and an anion, which constitutes molecular through bond breaking. This contrasts with atomic , such as the electron loss from a sodium atom (Na → Na⁺ + e⁻), which occurs without involving a . Heterolysis thus emphasizes bond-specific charge separation, often favored in polar environments due to differences between atoms. The concept of dissociation further connects heterolysis to broader ionic phenomena, distinguishing heterolytic dissociation of covalent molecules from electrolytic dissociation of ionic compounds. Heterolytic dissociation involves the breaking of a into oppositely charged ions, serving as the initial molecular-level step in forming salts from covalent precursors, such as acids or bases ionizing in solution. In contrast, electrolytic dissociation refers to the separation of pre-existing ions in salts like NaCl when dissolved, without bond cleavage, allowing the solution to conduct . Heterolysis thus underlies the transition from covalent to ionic character in many systems. A representative example is the heterolytic dissociation of hydrogen chloride (HCl) in aqueous solution, where the H–Cl bond cleaves to yield H⁺ and Cl⁻ ions, enabling electrolytic conduction and linking molecular heterolysis to observable ionic behavior./01%3A_Chapters/1.33%3A_Radical_Reactions) This process highlights how heterolysis facilitates salt formation and ionization at the bond level. While heterolysis specifically targets covalent bonds, general ionization can involve electron ejection from molecular orbitals without bond rupture, as in photoelectron spectroscopy, underscoring the bond-centric nature of heterolytic processes.

Influencing Factors

Solvation Effects

Polar solvents play a crucial role in facilitating heterolytic bond cleavage by solvating the resulting cations and anions through ion-dipole interactions, which stabilize the charged species and thereby lower the energy barrier for the process. This stabilization is particularly evident in the heterolytic decomposition of tert-butyl halides, where solvent polarity enhances charge separation in the , accelerating the . The dielectric constant of the significantly influences heterolysis by modulating the electrostatic interactions between . with high dielectric constants, such as (ε ≈ 80), effectively screen charges and reduce ion pairing, promoting the formation of free over tightly bound pairs. In contrast, non-polar with low dielectric constants provide insufficient stabilization, making heterolysis rare and often resulting in persistent ion pairs rather than dissociated . Protic solvents, like and alcohols, excel at stabilization through bonding, which both cations and anions more effectively than in aprotic media, as seen in the heterolysis of tert-alkyl halides where protic environments correlate with higher reaction rates. Aprotic solvents, such as (DMSO), rely primarily on their polarity for and tend to favor the stabilization of certain anions due to weaker specific interactions, leading to distinct sensitivities in heterolysis reactions compared to protic solvents. This difference is quantified in multiparametric analyses, where protic solvents exhibit greater influence on anion via bonding.

Thermodynamic and Kinetic Aspects

Heterolytic bond cleavage involves the breaking of a such that one fragment retains both electrons, resulting in the formation of oppositely charged species. The bond dissociation energy (BDE) for this process, defined as the standard change for the reaction AB → A⁺ + B⁻ in the gas phase, is substantially higher than for homolytic cleavage due to the energetic cost of charge separation. For instance, in methyl chloride (CH₃Cl), the homolytic BDE for CH₃–Cl → CH₃• + Cl• is approximately 351 kJ/mol, whereas the heterolytic BDE for CH₃Cl → CH₃⁺ + Cl⁻ is about 942 kJ/mol, reflecting the additional energy required to generate free ions without stabilization. The thermodynamics of heterolysis are governed by the change (ΔG) for the dissociation equilibrium AB ⇌ A⁺ + B⁻, where the K is given by K = [A⁺][B⁻]/[AB], and ΔG = -RT ln K. This ΔG encompasses the heterolytic BDE as the dominant contribution to ΔH, along with an entropic term TΔS that favors dissociation due to increased molecular freedom, though the large positive ΔH typically renders K very small in the gas phase. For example, the high heterolytic BDE leads to ΔG values on the order of hundreds of kJ/mol, making spontaneous heterolysis unfavorable without external stabilization. Kinetically, heterolytic cleavage proceeds via a featuring partial charge development on the separating fragments, which raises the (Ea) compared to homolysis. The rate constant k follows the : k=Ae−Ea/RTk = A e^{-E_a / RT} where A is the , R is the , and T is temperature; the partial charges in the make Ea sensitive to environmental factors, such as polar media that can lower it through electrostatic stabilization. Substituent effects play a crucial role in modulating the by altering stability; electron-donating groups, particularly those enabling delocalization (e.g., phenyl s stabilizing carbocations), reduce the heterolytic ΔH by 50–100 kJ/mol or more relative to unsubstituted analogs. This stabilization shifts the equilibrium toward s and lowers Ea, facilitating heterolysis in reactions involving stabilized species.

Historical Context

Early Observations

The theory of electrolytic dissociation proposed by in 1887 provided an early framework for understanding ionic processes in solution, indirectly laying groundwork for recognizing heterolytic cleavage as distinct from neutral dissociation in aqueous media. By the , empirical observations in highlighted heterolysis through reactions such as the of alkyl halides, where substitution products suggested the formation of charged species rather than even bond splitting. These findings underscored that bond breaking in such systems favored one atom retaining both electrons, aligning with later interpretations of heterolytic paths. Although the term "heterolysis" was not coined until the 1930s by Christopher Ingold and Edward Hughes to describe this uneven distribution in bond fission, conceptual precursors appeared in 's 1890 strain theory, which attributed heightened reactivity in small-ring cycloalkanes to angular distortions that facilitated polar bond cleavage under stress. In 1900, Moses Gomberg demonstrated free radicals from triphenylmethyl compounds, which was contrasted by and Victor Villiger's 1902 isolation of the triphenylmethyl via heterolytic dissociation of the corresponding chloride, highlighting ionic mechanisms in substitution reactions.

Development of the Concept

The formalization of heterolysis as a key mechanistic process in occurred in the 1930s through the pioneering work of Edward D. Hughes and Christopher K. Ingold. In their 1935 publication, they proposed the SN2 mechanism for bimolecular nucleophilic substitutions, describing a concerted heterolytic cleavage where the entering displaces the with both electrons of the bond moving to the latter, forming an ion pair intermediate. This was extended in their 1937 paper on reaction kinetics and the Walden inversion, introducing the SN1 mechanism, which features a unimolecular rate-determining step involving heterolytic bond fission to generate a free , followed by nucleophilic attack. These mechanisms provided the first systematic framework for understanding polar bond breaking in substitution reactions, emphasizing the role of asymmetry in solution-phase processes. Quantum mechanical insights into heterolysis advanced in the post-1940s era with the application of , which elucidated the movement of electron pairs during bond cleavage. Building on earlier foundations, Erich Hückel's 1931 quantum theoretical contributions to the problem demonstrated how delocalized π-electron systems confer stability to aromatic compounds, resisting heterolytic disruption due to the required to localize electrons. This work, integrated into valence bond descriptions by the 1940s, highlighted how and orbital overlap influence the feasibility of heterolytic pathways in conjugated systems, providing a theoretical basis for the stability of intermediates like carbocations in electrophilic aromatic substitutions. A significant advancement came in the through Louis P. Hammett's contributions to , where he quantified effects on heterolysis rates using linear free energy relationships (LFERs). Extending his 1937 , which correlated influences on the of benzoic acids—a classic heterolytic process—Hammett's analyses in the applied LFERs to solvolysis reactions, revealing how electron-withdrawing groups accelerate heterolytic cleavage by stabilizing transition states. These relations, expressed as log(K/K₀) = ρσ (where ρ measures reaction sensitivity and σ quantifies electronic effects), enabled predictive modeling of heterolysis kinetics across diverse substrates. By the 1980s, the concept evolved from empirical and semi-empirical models to advanced computational frameworks, with quantum chemical methods confirming heterolytic behaviors in both gas-phase and solution environments. Early gas-phase studies using Hartree-Fock calculations demonstrated lower energy barriers for heterolysis without solvation, contrasting with solution-phase models incorporating implicit solvents that stabilize ions and alter rates. This shift, exemplified by computations on SN1-like dissociations, underscored the solvent's role in modulating electron pair transfer, bridging theoretical predictions with experimental observables.

Applications and Examples

In Organic Chemistry Reactions

Heterolysis is pivotal in numerous polar organic reactions, where the unequal cleavage of bonds generates ionic intermediates that drive substitution, elimination, and processes. These mechanisms rely on the formation of electron-deficient species, such as carbocations, which are stabilized by inductive effects, , or , making heterolysis thermodynamically more favorable in polar solvents for many transformations. In the SN1 mechanism, the rate-determining step involves the heterolytic dissociation of the carbon-leaving group (C-LG) bond, producing a and the departing anion. This unimolecular process is , dependent solely on the substrate concentration, as established through kinetic studies by Hughes and Ingold in . A classic example is the solvolysis of in , where the tertiary C-Cl bond undergoes heterolysis to form the stable tert-butyl and , followed by rapid nucleophilic attack by to yield the alcohol product after . The key step can be represented as: \ceR−X−>[slow]R++X−\ce{R-X ->[slow] R^+ + X^-} Subsequent combination with a nucleophile (Nu⁻) forms the substitution product. This mechanism predominates for tertiary substrates due to the stability of the resulting carbocation. The E1 elimination mechanism similarly features heterolytic bond cleavage, beginning with the departure of the leaving group from the substrate to generate a carbocation intermediate, followed by the fast heterolytic removal of a β-proton to form an alkene. Like SN1, it is unimolecular and often competes with substitution under similar conditions, with product distribution influenced by the stability of the alkene formed. An illustrative case is the acid-catalyzed dehydration of 2-butanol, where protonation of the hydroxyl group facilitates heterolysis of the C-OH₂⁺ bond, yielding a secondary carbocation that loses a proton from an adjacent carbon to produce butene isomers. Electrophilic addition reactions to alkenes also depend on heterolysis, particularly in the initial or addition step that breaks the π-bond asymmetrically to form a . This is exemplified by the addition of HBr to propene, which adheres to : the proton attaches to the less substituted carbon, generating the more stable secondary on the terminal carbon, which then captures bromide to form . The heterolytic nature of the π-bond cleavage ensures based on stability, a principle elucidated in early 20th-century studies on acid additions. Heterolysis underpins the majority of polar organic mechanisms, including these examples, by enabling the generation of reactive ionic that facilitate bond formation in a controlled manner.

In Biochemical and Industrial Processes

In biochemical processes, heterolysis plays a crucial role in by facilitating the formation of ionic intermediates that enable precise bond cleavage in aqueous environments. For instance, in serine proteases such as , the nucleophilic attack by the serine residue on the carbonyl carbon of a substrate forms a tetrahedral intermediate, followed by heterolytic cleavage of the C-N bond to generate an acyl-enzyme intermediate. This step allows for the selective of bonds, essential for protein degradation and signaling pathways. Similarly, involves heterolytic cleavage of the Pγ–Oβ bond, where nucleophilic attack by water leads to the release of inorganic phosphate and ADP, powering energy-dependent cellular processes like and . The prevalence of heterolysis in biochemical systems is particularly advantageous in aqueous environments, where polar molecules stabilize charged transition states and intermediates, promoting selective reactivity over competing homolytic pathways. This solvation-driven selectivity ensures high efficiency in active sites, minimizing side reactions and enabling under mild physiological conditions. In industrial applications, heterolysis underpins key processes for resource conversion and material synthesis. Acid-catalyzed cracking relies on heterolytic dissociation of C-C bonds over catalysts like zeolites, generating intermediates that drive skeletal rearrangements and fragmentation to produce lighter hydrocarbons such as gasoline-range fractions. Likewise, of alkenes, such as isobutyl vinyl ether, initiates via heterolytic cleavage of a carbon-halogen bond in adducts formed from halides and monomers, propagating chain growth to yield polymers with controlled molecular weights for adhesives and coatings. A specific example is biodiesel production through base-catalyzed transesterification, where alkoxide ions attack the carbonyl of triglycerides, forming a tetrahedral intermediate that undergoes heterolysis of the ester C-O bond to yield fatty acid methyl esters and glycerol. In scaling up these industrial heterolytic processes, solvation effects are optimized to enhance efficiency; for instance, explicit solvent modeling in liquid-phase reactions reveals that hydrogen bonding stabilizes transition states, reducing activation barriers by up to 0.46 eV in acid-catalyzed cleavages and improving yields in biomass-derived feedstocks.

References

  1. http://www.chem.ucla.edu/~harding/IGOC/H/heterolytic_cleavage.html
  2. https://open.maricopa.edu/fundamentalsoforganicchemistry/chapter/9-1-homolytic-and-heterolytic-cleavage/
  3. https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/chapt4.htm
  4. https://kpu.pressbooks.pub/organicchemistry/chapter/9-1-homolytic-and-heterolytic-cleavage/
  5. https://www.chemistrysteps.com/homolytic-and-heterolytic-bond-cleavage/
  6. https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/react1.htm
  7. https://www.utdallas.edu/~scortes/ochem/OChem1_Lecture/Class_Materials/11_acid_base_chem.pdf
  8. https://byjus.com/chemistry/homolytic-and-heterolytic-fission/
  9. https://www.chemistrysteps.com/initiation-propagation-termination-in-radical-reactions/
  10. http://www.chem.ucla.edu/~harding/IGOC/I/ionization.html
  11. https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/07%3A_Periodic_Properties_of_the_Elements/7.04%3A_Ionization_Energy
  12. https://oyc.yale.edu/chemistry/chem-125b/lecture-4
  13. https://www.sciencedirect.com/topics/chemistry/electrolytic-dissociation
  14. https://pubs.acs.org/doi/10.1021/jo00328a012
  15. https://link.springer.com/article/10.1134/S1070363207090095
  16. https://academic.oup.com/bcsj/article-abstract/67/3/831/7348900
  17. https://webbook.nist.gov/cgi/cbook.cgi?ID=C74873&Mask=1
  18. https://webbook.nist.gov/cgi/cbook.cgi?ID=24917&Mask=1
  19. https://pubs.rsc.org/en/content/articlelanding/2020/cs/d0cs00405g
  20. https://www.sciencedirect.com/science/article/abs/pii/S2210271X12002198
  21. https://pubs.acs.org/doi/10.1021/ja00048a042
  22. https://www.britannica.com/biography/Svante-Arrhenius
  23. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_(Morsch_et_al.)/04:_Organic_Compounds-_Cycloalkanes_and_their_Stereochemistry/4.03:_Stability_of_Cycloalkanes_-_Ring_Strain
  24. https://www.acs.org/education/whatischemistry/landmarks/freeradicals.html
  25. https://www.sciencedirect.com/science/article/abs/pii/S266710932400352X
  26. https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.199627501
  27. https://link.springer.com/content/pdf/10.1007/978-1-4615-8660-9.pdf
  28. https://cdnsciencepub.com/doi/pdf/10.1139/v92-054
  29. https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/mas.20223
  30. https://books.rsc.org/books/monograph/1549/chapter/978512/Enzyme-Models-Classified-by-Reaction
  31. https://pubs.acs.org/doi/10.1021/ja507169f
  32. https://www.sciencedirect.com/science/article/abs/pii/S1367593114000295
  33. https://pubs.acs.org/doi/10.1021/ma402490f
  34. https://www.sciencedirect.com/science/article/abs/pii/S0016236122031337
  35. https://pubs.acs.org/doi/10.1021/acscatal.7b04367
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