Insights into the Reaction Mechanism of Criegee Intermediate CH2OO

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Insights Into the Reaction Mechanism of Criegee Intermediate CH2OO with Methane and Implications for the Formation of Methanol Kaining Xu, Weihua Wang, Wenjing Wei, Wenling Feng, Qiao Sun, and Ping Li J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b05858 • Publication Date (Web): 30 Aug 2017 Downloaded from http://pubs.acs.org on August 30, 2017

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The Journal of Physical Chemistry

Insights Into the Reaction Mechanism of Criegee Intermediate CH2OO with Methane and Implications for the Formation of Methanol Kaining Xua, Weihua Wang*,a, Wenjing Weia, Wenling Fenga, Qiao Sunb, and Ping Li*,a a

Key Laboratory of Life-Organic Analysis, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, 273165, P. R. China b

Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, School for Radiological and Interdisciplinary Sciences, Soochow University, Suzhou, 215123, P. R. China E-mails: [email protected] (Weihua Wang) and [email protected] (Ping Li)

ABSTRACT: Criegee intermediates (CIs) play a key role in controlling the atmospheric budget of hydroxyl radical, organic acids, and secondary organic aerosols. In this study, the detailed reaction mechanisms of the simplest Criegee intermediate CH2OO and its derivatives with methane (CH4) have been systematically investigated theoretically. Two pathways A and B have been identified for the title reaction. In pathway A, CIs can act as an oxygen donor by inserting its terminal oxygen atom into the C-H bond of alkanes, resulting in the formation of alcohol species. The corresponding energy barriers ranging from 6.5 to 24.1 kcal/mol are associated with the O-O bond strength of CIs. Meanwhile, this pathway is more favorable thermodynamically, where the free energy changes (enthalpy changes) range from -81.1 (-78.3) to -110.9 (-109.0) kcal/mol, respectively. In pathway B, addition reaction to produce the hydroperoxides occurs, accompanying with the hydrogen transfer from the alkanes to the terminal oxygen atom of CIs. The corresponding energy barriers ranging from 17.3 to 30.9 kcal/mol are higher than those in pathway A. Further calculations of the rate constants suggest that pathway A is the most favorable reaction channel and the rate constant exhibits a positive temperature dependence. In addition, the conformation-dependent reactivity for the title reaction has been observed. The present findings can enable us to better understand the potential reactivity of CIs in the presence of the alkane species.

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1. INTRODUCTION Alkenes are a class of volatile organic compounds that are emitted to the Earth’s troposphere in very large amounts from biogenic and anthropogenic sources.1 Their major degradation paths are reactions initiated with OH, NO3, Cl, and O3. Especially, the reactions of alkenes with O3 in the gas phase have been paid extensive attentions increasingly since the gas-phase alkene ozonolysis is recognized as an important atmospheric sink for the tropospheric alkenes. Moreover, it has been proven that this reaction is an important source of HOx(x=1,2) radicals, hydroperoxides, carboxylic acids. As shown in Scheme 1, it is nowadays accepted that the reaction between O3 and alkenes follows the Criegee mechanism2 and is initiated with a 1,3-cycloaddition of O3 to the C=C double bond of the alkenes to form the cyclic primary ozonide (POZ). Subsequently, the POZ decomposes to form the carbonyl oxides (so-called Criegee intermediates) and a carbonyl compound due to the large exothermicity of this reaction. After that, the internally excited CI will either decompose unimolecularly (about 37-50%) or become collisionally stabilized CI (sCI, about 50-63%).3-5 For these stabilized CIs, they may still react with the other atmospheric species via the unimolecular or bimolecular reaction channels due to their high reactivity. Here, these secondary reactions are thought to have an important effect on the earth's climate and human health.6-7 In addition, the CIs are also implicated in the reaction cycles of flavin-dependent Baeyer–Villiger monooxygenases that provide a green route for synthesizing enantiopure drug compounds. 8 Given the importance of CIs, more and more studies have focused on the reactivity of CIs experimentally and theoretically. Generally, they have eluded detection in the gas phase due to their high reactivity until they have been directly detected and produced experimentally.9-11 The direct experimental determination of bimolecular rate constants for the CIs reactions with atmospheric trace gas species have also become possible.12-19 Thus, the direct generation, detection, and reactions of the CIs have sparked a renewed interest in Criegee chemistry.19-29 On the other hand, the reactivity of CIs is still not fully understood because the data derived from their direct observation are limited. Alternatively, theoretical studies based on the quantum chemistry have become an effective tool increasingly to predict and elucidate the geometries and chemical reactivity of CIs especially for those beyond the experimental 2


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detections.30-52 As for the bimolecular reactions involving CIs, they are recognized to be the key processes in the formation of aerosols in the atmosphere. On the one hand, CIs can act as an oxidant by transferring an oxygen atom to CO or NO,46,49 resulting in the formation of a carbonyl compound (aldehyde or ketone depending on the CIs) and CO2 or NO2. Especially, the oxidation of SO2 via CIs is an important source of sulfuric acid, which plays an important role in aerosol nucleation.6-7,25,53-54 Similarly, NO2 also can abstract the terminal oxygen of CIs to form a nitrate radical and a carbonyl species.16,55 All these reactions demonstrate that CIs are a good oxygen atom donor. On the other hand, addition reactions can also take place between CIs and atmospheric species,14,31-40,42-45,53-54 accompanying with the hydrogen transfer from small molecules to the terminal oxygen atom of CIs if atmospheric species contain hydrogen atoms. For example, CIs can react with water,31-36 aldehydes,39 ammonia,42 and hydrogen sulfide,14 resulting in the formation of the hydroxy-hydroperoxide, secondary ozonide, or hydroperoxide alkylamine, etc. Undoubtedly, these findings suggest that CIs have two reactive sites for the addition reactions, namely the carbon atom and the terminal oxygen atom. As a widespread atmospheric species and long-lived greenhouse gas second only to CO2, methane (CH4) not only plays an important role in global carbon cycle and energy utilization, but also has an important influence on atmospheric chemistry and climate. The continuous growth of CH4 annually has received more and more attentions increasingly, where the atmospheric CH4 reached 256% of its pre-industrial level in 2015 due to increased emissions from anthropogenic sources according to the reports of the World Meteorological Organization (WMO). Given the high reactivity of CIs and the specific geometry of CH4 containing H atoms, we wonder if CIs can react with CH4 and its derivatives through the bimolecular reactions mentioned above. If so, how about the microscopic details for the whole reaction? Moreover, how about the substitution effects on the reactivity of CIs? Obviously, the clarification of the above questions will enable us a better understanding of the reactivity of CIs with alkanes. In the lack of the relevant experimental studies, a theoretical investigation on the title reaction appears to be highly desirable. 3



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Therefore, to better explore the reactivity of CIs with the alkane species, in this study, the reactions between CH2OO and CH4 as well as its derivatives have been systematically investigated employing density functional theory (DFT). To the best of our knowledge, no relevant studies have been reported previously. Given the fact that different CIs can be produced in the ozonolysis of different alkenes and the nature and position of the substituents in CIs may affect their reactivity,32 so the substitution effects of halogenation and alkylation for CIs have also been explored, where most of them exist in nature or have been prepared experimentally.11,19,26,32,56 As a result, the present findings not only can provide helpful clues to the relevant experiments about the potential reactivity of CIs, but also can reveal an alternative approach for the conversion of alkane to alcohol species using the CIs.

2. COMPUTATIONAL DETAILS In this study, given the fact that fifty reaction pathways have been considered and the sizes of the selected systems are large, so the compromise between the accuracy and computational cost should be considered in the choice of the computational method to ensure the normal proceeding of the relevant calculations. In view of the fact that the B3LYP method within the framework of the density functional theory (DFT) has been widely employed to study a variety of CI systems since it can provide many properties comparable in accuracy to higher levels of theory at a modest cost of computing time and disk space,14-15,19,31-39,41-47,57-58 so all the geometries have been fully optimized at the B3LYP/6-311++G(d,p) level of theory. As reported previously,20-22,30-36,41-52 the CIs can be treated as a closed-shell species. Actually, for the reactions of the CIs with ammonia,42 formic acid,43 and sulfuric acid,44 the obtained UB3LYP and B3LYP results for the energies and vibrational wavenumbers were identical. Subsequently, vibrational frequency analysis was performed at the same level of theory to identify the nature of the optimized structures. In addition, anharmonic analyses have also been performed for the transition states to evaluate the reasonableness of the implicit harmonic approximation employing the keyword “Freq=Anharmonic”. As a result, slight differences have been observed for the tunneling corrections between harmonic and anharmonic values (1.32 versus 1.38 in the pathway A mentioned below). So, all the results are obtained on the basis of the harmonic approximation if not noted otherwise. 4


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For the calculated transition states, further intrinsic reaction coordinate (IRC)59,60 calculations were performed to verify that the transition states indeed connect the initial reactants and products. To further refine the calculated energies, single-point energy calculations have been performed employing the CCSD(T) method on the basis of the optimized geometries at the B3LYP/6-311++G(d,p) level of theory. Depending on the sizes of the reaction systems, CCSD(T)/AUG-cc-pVTZ and CCSD(T)/AUG-cc-pVDZ levels of theory have been employed for the reactions involving CH4 and the other reactions, respectively. To evaluate the interaction strength between CH2OO and CH4 in the initial pre-reactive complex, the interaction energies are defined as the energy differences between the formed complexes and the corresponding monomers, which are further corrected by the zero-point vibrational energy (ZPVE) and basis set superposition errors (BSSEs). Here, the Boys-Bernardi counterpoise technique has been employed to evaluate the BSSEs.61 To qualitatively evaluate the structural changes of transition states relative to the reactants, the deformation energy has been calculated for CH4, which is defined as the energy difference between the CH4 at the geometry of transition state and the isolated CH4. Obviously, the larger the deformation energy is, the larger the geometric changes are. To better clarify the formation and nature of the intermolecular interactions between CIs and CH4, the atoms in molecules (AIM) theory has been employed. According to the AIM theory,62 the interatomic interaction is indicated by the presence of a bond critical point (BCP). The corresponding strength can be estimated from the magnitude of the electron density (ρbcp) at the BCP. Similarly, the ring structure can be confirmed by the existence of a ring critical point (RCP). Moreover, the nature of the interatomic interaction can be predicted from the topological parameters at the BCP, such as the Laplacian of (∇2ρbcp) and energy density (Hbcp), where the Hbcp is composed of the potential energy density (Vbcp) and kinetic energy density (Gbcp). Namely, the interatomic interactions may be characterized by the ionic bonds, H-bonds, and van der Waals interactions (closed-shell interaction) if ∇2ρbcp > 0. Otherwise, the interatomic interactions are the covalent bonds (shared interaction) if ∇2ρbcp < 0. To further confirm the presence of the intermolecular interactions in the formed 5



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pre-reaction complex, the plot of the reduced density gradient (RDG) versus the electron density multiplied by the sign of the second Hessian eigenvalue for the pre-reactive complex has been constructed, which has been widely used to identify the noncovalent interactions.63,64 To obtain the rate constant of the title reaction, the transition-state theory has been employed in combination with the Wigner tunneling correction. All of them have been completed using KiSThelP program.65 All the calculations have been performed using Gaussian 09 program66 except for the reaction rate constants.

3. RESULTS AND DISCUSSION As shown in Scheme 2, two reaction pathways, named as pathway A and pathway B, have been outlined. Correspondingly, alcohols and hydroperoxides have been produced, respectively. Considering the similarity of the reaction mechanism between different CIs and CH4, we will mainly discuss the representative reaction of CH2OO with CH4 for simplicity. 3.1 Reaction of CH2OO with CH4 3.1.1 Pathway A As the first step of the reaction pathway A, an initial pre-reactive complex labeled as IMa has been located. As shown in Figure 1, IMa is characterized by an intermolecular H-bond formed between the terminal oxygen atom of CH2OO and one of the hydrogen atoms of CH4, which can be confirmed by the presence of the BCP as shown in Figure S1 of the Supporting Information (SI). Moreover, as displayed in Figure S2 of the SI, the hydrogen bonding interaction can be further confirmed by the presence of the corresponding spike denoting the intermolecular hydrogen bond. Here, the larger H-bond distance of 2.675 Å suggests that the H-bonding interaction here should be weak. Actually, this point can be further reflected from the small electron density at the BCP of the H-bond. Moreover, the positive ∇2ρbcp and Hbcp values at the BCP of the H-bond suggest that the H-bonding interaction should be governed by the electrostatic interactions. Correspondingly, the insignificant geometric changes for CH2OO and CH4 fragments have been observed compared with their isolated states. For example, the O3-O4 bond of CH2OO and C5-H7 bond of CH4 participating in the H-bond have been elongated by only about 0.001 Å upon complexation. Moreover, the weak 6


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interaction between CH2OO and CH4 has also been confirmed by the calculated interaction energy of -1.0 kcal/mol considering the BSSE corrections. The enthalpy and Gibbs free energy changes in the formation process of IMa are 0.1 and 2.1 kcal/mol, respectively. Thus, the formation of the IMa is unfavorable thermodynamically. After the formation of the unstable IMa, the reaction proceeds through the transition state TSa to form the methanol and formaldehyde, where TSa has an unique imaginary frequency of 559.1i cm−1. Compared with IMa, the O3-O4 and C5-H7 bonds mentioned above have been further elongated and the terminal O4 atom of CH2OO gradually approaches the H7 atom of CH4. As a result, the strengths of the O3-O4 and C5-H7 bonds have been significantly weakened. On the contrary, the H-bonding interaction of O4···H7 bond has been strengthened. As shown in Table S1 of the SI, these phenomena can be confirmed by the decreasing ρbcp at the BCPs of the O3-O4 and C5-H7 bonds and the increasing ρbcp for that of the O4···H7 bond, respectively. To investigate the reaction mechanism of pathway A, IRC calculation has been performed on the basis of TSa. Correspondingly, the changes of the potential energy and the selected structural parameters along with the reaction coordinates have been given in Figures 2 and 3, respectively. So, the detailed reaction mechanism can be described as follows. Namely, CH2OO and CH4 approach each other through the intermolecular H-bond formed between the terminal O* atom of CH2OO and the H* atom of CH4, where an unstable initial pre-reactive complex can be formed. With the proceeding of the reaction, the O-O bond of CH2OO gradually breaks and the terminal O* atom has been dissociated from CH2OO. After then, the dissociated O* atom abstracts the H* atom of the CH4, resulting in the formation of the OH and CH3 fragments. Finally, both radicals interact with each other to form methanol. Therefore, the final products in pathway A are methanol and formaldehyde. In addition, as shown in Figure 3, the elongation of the O-O* (i.e., O3-O4) bond of CH2OO is more significant relative to that of the C-H* (i.e., C5-H7) bond of CH4 before approaching the transition state, where no obvious changes have been observed for the C-H* bond in this period. Therefore, the strength of the O-O bond in CH2OO should be the main factor influencing the reactivity of pathway A. This point can be further confirmed by the observed 7



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correlation between the energy barrier and the O-O bond strength mentioned below. As presented in Table 1, the calculated enthalpy and Gibbs free energy changes of the whole reaction process are -82.0 and -83.9 kcal/mol, suggesting that the pathway A is a more exothermic and spontaneous process. Therefore, the proceeding of the reaction is favorable thermodynamically. Kinetically, the energy barrier is 22.6 kcal/mol, which can be further reduced more or less upon substitution as mentioned below. 3.1.2 Pathway B Similar to pathway A, an initial pre-reactive complex, namely IMb, has been located in the first step of the reaction. As displayed in Figure S1 of the SI, IMb is characterized by the intermolecular H-bond from the presence of the BCP between CH2OO and CH4. The larger H-bond distance of 2.583 Å suggests that the H-bond should be weak, which can be confirmed by the small electron density at the BCP of the H-bond. As shown in Table S1 of the SI, the positive ∇2ρbcp and Hbcp values at the BCP of H-bond suggest that the H-bond should be governed by the electrostatic interactions. As a result, no obvious geometrical changes occur for CH2OO and CH4 relative to their isolated states. Moreover, the calculated interaction energy of -1.3 kcal/mol and the positive changes of the enthalpy and Gibbs free energy (-0.7 and 3.4 kcal/mol) during the formation process suggest that the formation of IMb is unfavorable thermodynamically. With the proceeding of the reaction, the transition state TSb has been located. Compared with IMb, larger geometric changes can be observed. For example, the terminal O atom of CH2OO has deviated from the original molecular plane and the O-O bond has been elongated by about 0.051 Å. Meanwhile, the C-H bond of CH4 involved in the H-bond has been elongated by 0.206 Å, implying the dissociation of the H atom. On the contrary, both the C atoms of the CH2OO and CH4 approach each other gradually, where the contact distance between two C atoms have been decreased by 1.566 Å to 2.208 Å. Similarly, the H-bond distance has also been decreased to 1.351 Å. To clarify the reaction mechanism of pathway B, IRC calculation has been performed on the basis of TSb. Correspondingly, the changes of the potential energy and the selected structural parameters along with the reaction coordinates have been given in Figures 4 and 5, 8


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respectively. Obviously, both CH2OO and CH4 approach each other firstly along the direction of the formed intermolecular H-bond between them. The C-H* bond involved in the H-bond increases slowly initially and significantly near the transition state. However, slight increase for the O-O bond of CH2OO has been observed, implying that the C-H bond strength is an important factor determining the energy barrier of this pathway. With the cleavage of the C-H* bond of CH4, the H* and CH3 fragments have been produced. After then, the H* and CH3 fragments have been respectively coupled with the terminal O and C atoms of CH2OO, resulting in the formation of the hydroperoxyethyl. As shown in Figure 5, there is no obvious changes for the O-H* (i.e., O5-H8) bond relative to that of the C1-C6 bond after the transition state. Therefore, the H* atom addition to the terminal O atom of CH2OO is prior to the CH3 fragment addition to the C atom, exhibiting the non-cooperativity of the addition reaction. As presented in Table 1, the energy barrier of pathway B is 25.4 kcal/mol relative to the initial reactants, suggesting that it is difficult to proceed under normal conditions. On the contrary, the enthalpy and Gibbs free energy changes of pathway B are -46.8 and -37.2 kcal/mol, respectively, suggesting that this pathway is favorable thermodynamically. For the sake of comparison, the reaction profiles for the pathways A and B have been given in Figure 6. Obviously, the energy barrier of pathway B is higher by about 2.8 kcal/mol than that of the pathway A. Most probably, the high energy barrier for pathway B should be due to the stronger C-H bond of CH4 relative to that of the O-O bond of CH2OO since both bonds play a key role in determing the proceedings of the two reaction pathways. On the other hand, the calculated changes of the enthalpy and Gibbs free energy in the reaction pathway A are more negative than those of pathway B. Therefore, pathway A should be the predominated reaction channel kinetically and thermodynamically, which can be further confirmed by the other reactions below. 3.2 Reactions of CH2OO with other Alkanes To further validate the possibility of the reactions of CIs with other alkanes, the open-chain alkanes and cycloalkanes have been employed to react with CH2OO, where the alkanes employed here have been displayed in Figure S3 of the SI for reference. As expected, like the reaction of CH2OO with CH4, similar reaction mechanism has been observed for them. 9



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For the reactions of CH2OO with other alkanes according to the pathway A, some general rules can be observed as shown in Table 1. For example, all the reactions are exothermic and spontaneous processes thermodynamically. For the open-chain alkanes, the order of the relative reactivity is: tertiary C-H > secondary C-H > primary C-H from the calculated energy barriers. This point can be understood since the stability of the alkyl radical produced in the C-H dissociation process is the largest for the tertiary carbon radical followed by the secondary and primary carbon radicals. Here, the energy barrier of the reaction between CH2OO and the tertiary C-H bond of isopentane is only 11.0 kcal/mol. Moreover, the reactivity of the primary C-H bond at the different positions in isopentane is almost similar to each other. For the reactions between CH2OO and cycloalkanes, it was found that the reactivity increases with the increasing of the ring sizes, which can be owed to the favorable stability of the larger sizes of rings with small ring tension. For the reactions occurring according to the pathway B, all the energy barriers ranging from 16.2 to 23.0 kcal/mol are higher than those of the reactions of pathway A although the whole reactions are still favorable thermodynamically from the negative values of the enthalpy and Gibbs free energy changes. Therefore, the pathway B is less favorable relative to the pathway A for the reaction of CH2OO with alkanes. 3.3 Substitution Effects of CIs To evaluate the substitution effects of the different substituents on the title reaction, the reactions of the substituted CIs involving halogenation and alkylation with CH4 have been systematically investigated. For the substituted cases with the electron-releasing groups, the H atom of CH2OO has been respectively substituted with one and two methyl groups, where there are anti- and syn-CH3CHOO conformers for the monosubstituted case. For the pathway A, as illustrated in Figure 7 and Table 1, the energy barriers have been increased slightly except for anti-CH3CHOO. Here, the energy barrier involving anti-CH3CHOO has been decreased by about 2.0 kcal/mol relative to that of the title reaction. As for pathway B, similar to pathway A, the energy barriers have also been increased except for anti-CH3CHOO, which are still larger than those in pathway A. Similarly, the above analyses are also true for the enthalpy and 10


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Gibbs free energy changes in both pathways. Therefore, there is a slight influence of the electron-releasing groups on the title reaction overall. However, the substitution effects are more significant upon the introduction of the electron-withdrawing groups. As shown in Figure 7, the energy barriers of pathway A have been decreased significantly when the H atom of CH2OO is substituted with one and two halogen atoms. For example, the energy barriers have been decreased by 12.5(9.1), 8.0(3.7), and 7.6(3.2) kcal/mol upon introduction of one F, Cl, and Br atoms, respectively, where the data in parentheses refer to the results of the syn-conformers of CIs. Moreover, the energy barrier has been further decreased by 3.6 kcal/mol upon substitution with two F atoms. On the other hand, the halogenation effects on the pathway B are less obvious compared with those of the pathway A. For example, the energy barrier has been decreased by about 4.5, 3.0, and 3.5 kcal/mol for the anti-conformers of FCHOO, ClCHOO, and BrCHOO, respectively. On the contrary, the energy barrier has been increased by 3.5 and 3.1 kcal/mol for the syn-conformers of ClCHOO and BrCHOO, respectively. Obviously, the different effects of halogenation on the two reaction pathways should be mainly due to the different reaction mechanisms mentioned above. To clarify the correlation between the reactivity of CIs and their O-O bond strengths in pathway A, the dependence of the energy barrier versus the electron density at the BCP of the O-O bond has been explored, where only the halogenation effects have been included due to the slight influence of alkylation effects. As shown in Figure 8, the corresponding energy barriers increase with the increasing of the O-O bond strengths. From the viewpoint of the functional forms, the energy barrier decreases with the increasing of the ability of the electron-withdrawing substituents, which should be due to the significant weakening of the O-O bond upon introduction of the electron-withdrawing substituents. However, no clear trends have been observed for the electron-releasing substituents. Therefore, the reactivity of pathway A should be mainly controlled by the O-O bond strength of CIs, which is consistent with the above analyses of the reaction mechanism. Moreover, the relationship between the energy barrier and the deformation energy of CH4 has also been explored. As displayed in Figure S4 of the SI, the small deformation energy of 11



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CH4 suggests that the transition state more closely resembles the reactant, which is consistent with the Hammond’s postulate. At the same time, the energy barrier decreases with the decreasing of the deformation energy. In other words, for the exothermic reaction, the lower the energy barrier is, the more the geometry of the transition state resembles the reactant. In addition, as shown in Figure 7, all the energy barriers in pathway A are lower by about 2.8-10.8 kcal/mol than those of pathway B regardless of the introductions of the electron-withdrawing or electron-releasing substituents. Moreover, the reactivity of the anti-conformer of the CIs is higher than that of the syn-conformer from the calculated energy barriers, exhibiting the conformation-dependent reactivity of CIs with the alkanes. 3.4 Rate Constant Calculations To gain more kinetic information for the title reaction, the rate constants for pathways A and B have been calculated employing the conventional transition-state theory in combination with the Wigner tunneling correction. As listed in Table 2, the calculated rate constants of pathway A are much larger than those of pathway B at 298.15 K, further suggesting the predominance of the pathway A. Taking the reaction between CH2OO and CH4 as an example, the temperature dependence of the rate constant for pathway A has been given in Figure 9. Obviously, the rate constant increases with the increasing of the temperature, exhibiting the positive temperature dependence. Moreover, the calculated rate constant exhibits typical Arrhenius behavior within a large temperature range from 200 to 1200 K. Moreover, the Wigner tunneling correction at 298.15 K is 1.30, which is comparable to the more accurate Eckart tunneling correction of 1.38. As shown in Figure 9, the tunneling effect is more pronounced at low temperature. Similarly, the same is also true for pathway B. In the case of substituted CIs with electron-withdrawing groups, all the rate constants are larger than that of CH2OO more or less depending on the specific substitutes. For example, for the reaction of syn-ClCHOO with CH4, the rate constant is 6.27 × 10-26 cm3 molecule-1 s-1 for the pathway A. However, it increases to 4.46 × 10-17 cm3 molecule-1 s-1 for the reaction of F2COO with CH4. 3.5 Implications of the Results 12


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It is well known that the reaction of CIs with water vapor is one of the important sinks of CIs in the atmosphere because the water vapor is one of the most abundant trace gases in the atmosphere. Here, the reported rate constants for the reactions of CIs with water vapor range from 10-17 to 10-9 cm3 molecule-1 s-1 depending on the relative humidity of the environments.10,32,67-69 As for the present reactions of CIs with CH4, the calculated rate constants range from 10-30 to 10-17 cm3 molecule-1 s-1 depending on the nature and position of the substituents. Moreover, the globally averaged CH4 mole fraction calculated from in situ observations reached a new high of 1845±1 ppb (about 4.96 × 1013 molecule per cm3) in 2015 according to the reports of the World Meteorological Organization (WMO). Therefore, the reactions of CIs with CH4 could not compete with the corresponding reactions involving water vapor under normal conditions. However, given the larger rate constants for the reactions of the halogenated Criegee intermediates, the importance of the present reactions should not be ignored in the specific environmental conditions. For example, the higher concentration of CH4 can be expected in the specific areas emitting CH4, such as oil extraction, biomass burning, landfill place, or artificial environment. Therefore, despite the fact that no quantitative data for the concentrations of the halogenated Criegee intermediates are available, it is likely that the reaction of CIs with CH4 may play a certain role in some specific areas if the concentration of the CH4 reaches a certain level. In addition, according to the reaction mechanism of pathway A, it can lead to the formation of alcohol species. Hopefully, this reaction mechanism can provide helpful clues to the conversion of alkane to alcohol species experimentally. Certainly, some factors like the preparation of Criegee intermediates and some safety considerations should be resolved before the performance of the actual reactions. More sophisticated experiments are highly required to confirm the present results in the near future.

4. CONCLUSIONS In this study, the reaction mechanisms of the simplest Criegee intermediate CH2OO and its selected derivatives with CH4 and other alkanes have been systematically investigated in the gas phase theoretically. The main findings are summarized as follows: (1) Two reaction pathways A and B have been observed for the title reaction. In pathway 13



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A, the terminal O atom of CIs inserts into the C-H bond of alkanes, resulting in the formation of the corresponding aldehyde and alcohol species. As for pathway B, it is a bimolecular addition reaction, accompanying with the hydrogen transfer from CH4 to the terminal oxygen atom of CIs to produce the hydroperoxyethyl. Compared with pathway B, pathway A is the predominant reaction channel thermodynamically and kinetically. Moreover, the reactivity of pathway A is mainly controlled by the O-O bond strength of CIs. (2) The conformation-dependent reactivity has been observed for the CIs possessing antiand syn-conformers, i.e., the reactivity of the anti-conformer of CIs is higher than that of the syn-conformer. (3) The substitution effects on the reactivity of CIs are highly dependent on the nature of the substituted groups. Namely, the electron-withdrawing groups can significantly enhance the reactivity of CIs for pathway A. While the electron-releasing groups have a little effect on the reactivity. Expectedly, the present results can provide helpful information to better understand the CIs chemistry and the potential role of CIs in the specific regions. Meanwhile, the proposed reaction mechanism provides a new approach to the formation of the alcohol species. Certainly, more sophisticated experiments are required to further confirm these points in the future.

Supporting Information Available Molecular graphs and topological parameters for the pre-reactive complexes and transition states, plot of the RDG versus the electron density multiplied by the sign of the second Hessian eigenvalue for the pre-reactive complex IMa, the considered alkanes and substituted CIs, and the relationship between the energy barrier and deformation energy of CH4 in the transition state.

ACKNOWLEDGMENTS This work is supported by NSFC (21577076, 21303093, and 21003082), the NSF of Shandong Province (ZR2014BM020), and the Doctoral Foundation of Shandong Province (ZR2017BB055). 14


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REFERENCES (1) Wayne, R. P. Chemistry of atmospheres; Oxford University Press: Oxford, 3rd edn, 2000. (2) Criegee, R. Mechanism of ozonolysis. Angew. Chem. Int. Edit. 1975, 14, 745–752. (3) Horie, O.; Mortgat, G. K. Gas-phase ozonolysis of alkenes. Recent advances in mechanistic investigations. Accounts. Chem. Res. 1998, 31, 387–396. (4) Johnson, D.; Marston, G. The gas-phase ozonolysis of unsaturated volatile organic compounds in the troposphere. Chem. Soc. Rev. 2008, 37, 699–716. (5) Neeb, P.; Horie, O.; Moortgat, G. K. The ethene-ozone reaction in the gas phase. J. Phys. Chem. A 1998, 102, 6778–6785. (6) Stieb, D. M.; Judek, S.; Burnett, R. T. Meta-analysis of time-series studies of air pollution and mortality: Effects of gases and particles and the influence of cause of death, age, and season. J. Air. Waste. Manag. Assoc. 2002, 52, 470–484. (7) Kroll, J. H.; Seinfeld, J. H. Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere. Atmos. Environ. 2008, 42, 3593–3624. (8) Leisch, H.; Morley, K.; Lau, P. C. K. Baeyer-Villiger monooxygenases: More than just green chemistry. Chem. Rev. 2011, 111, 4165–4222. (9) Taatjes, C. A.; Meloni, G.; Selby, T. M.; Trevitt, A. J.; Osborn, D. L.; Percival, C. J.; Shallcross, D. E. Direct observation of the gas-phase Criegee intermediate (CH2OO). J. Am. Chem. Soc. 2008, 130, 11883–11885. (10) Welz, O.; Savee, J. D.; Osborn, D. L.; Vasu, S. S.; Percival, C. J.; Shallcross, D. E.; Taatjes C. A. Direct kinetic measurements of Criegee intermediate (CH2OO) formed by reaction of CH2I with O2. Science 2012, 335, 204–207. (11) Taatjes, C. A.; Welz, O.; Eskola, A. J.; Savee, J. D.; Scheer, A. M.; Shallcross, D. E.; Rotavera, B.; Lee, E. P. F.; Dyke, J. M.; Mok, D. K. W., et al. Direct measurements of conformer-dependent reactivity of the Criegee intermediate CH3CHOO. Science 2013, 340, 177–180. (12) Foreman, E. S.; Kapnas, K. M.; Murray, C. Reactions between Criegee intermediates and the inorganic acids HCl and HNO3: Kinetics and atmospheric implications. Angew. Chem. Int. Edit. 2016, 55, 10419–10422. (13) Taatjes, C. A.; Shallcross, D. E.; Percival, C. J. Research frontiers in the chemistry of Criegee intermediates and tropospheric ozonolysis. Phys. Chem. Chem. Phys. 2014, 16, 1704–1718. (14) Smith, M. C.; Chao, W.; Kumar, M.; Francisco, J. S.; Takahashi, K.; Lin, J. J. Temperature-dependent rate coefficients for the reaction of CH2OO with hydrogen sulfide. J. Phys. Chem. A 2017, 121, 938–945. (15) Su, Y. T.; Lin, H. Y.; Putikam, R.; Matsui, H.; Lin, M. C.; Lee, Y. P. Extremely rapid self-reaction of the simplest Criegee intermediate CH2OO and its implications in atmospheric chemistry. Nat. Chem. 2014, 6, 477–483. (16) Ouyang, B.; McLeod, M. W.; Jones, R. L.; Bloss, W. J. NO3 radical production from the reaction between the Criegee intermediate CH2OO and NO2. Phys. Chem. Chem. Phys. 2013, 15, 17070–17075. (17) Smith, M. C.; Chao, W.; Takahashi, K.; Boering, K. A.; Lin, J. J. Unimolecular decomposition rate of the Criegee intermediate (CH3)2COO measured directly with UV absorption spectroscopy. J. Phys. Chem. A 2016, 120, 4789–4798. (18) Smith, M. C.; Chang, C. H.; Chao, W.; Lin, L. C.; Takahashi, K.; Boering, K. A.; Lin, J. J. Strong negative temperature dependence of the simplest Criegee intermediate CH2OO reaction with water dimer. J. Phys. Chem. Lett. 2015, 6, 2708–2713. (19) Lin, H.Y.; Huang, Y. H.; Wang, X. H.; Bowman, J. M.; Nishimura, Y.; Witek, H. A.; Lee, Y. P. Infrared identification of the Criegee intermediates syn- and anti-CH3CHOO, and their 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

distinct conformation-dependent reactivity. Nat. Commun. 2015, 6, 7012. (20) Su, Y. T.; Huang, Y. H.; Witek, H. A.; Lee, Y. P. Infrared absorption spectrum of the simplest Criegee intermediate CH2OO. Science 2013, 340, 174–176. (21) Li, H. W.; Fang, Y.; Kidwell, N. M.; Beames, J. M.; Lester, M. I. UV photodissociation dynamics of the CH3CHOO Criegee intermediate: Action spectroscopy and velocity map imaging of O-atom products. J. Phys. Chem. A 2015, 119, 8328–8337. (22) Miliordos, E.; Xantheas, S. S. The origin of the reactivity of the Criegee intermediate: Implications for atmospheric particle growth. Angew. Chem. Int. Edit. 2016, 55, 1015–1019. (23) Taatjes, C. A.; Welz, O.; Eskola, A. J.; Savee, J. D.; Osborn, D. L.; Lee, E. P. F.; Dyke, J. M.; Mok, D. W. K.; Shallcross, D. E.; Percival, C. J. Direct measurement of Criegee intermediate (CH2OO) reactions with acetone, acetaldehyde, and hexafluoroacetone. Phys. Chem. Chem. Phys. 2012, 14, 10391–10400. (24) Beames, J. M.; Liu, F.; Lu, L.; Lester, M. I. Ultraviolet spectrum and photochemistry of the simplest Criegee intermediate CH2OO. J. Am. Chem. Soc. 2012, 134, 20045–20048. (25) Huang, H. L.; Chao, W.; Lin, J. J. Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO2. Proc. Natl. Acad. Sci. USA 2015, 112, 10857–10862. (26) Beames, J. M.; Liu, F.; Lu, L.; Lester, M. I. UV spectroscopic characterization of an alkyl substituted Criegee intermediate CH3CHOO. J. Chem. Phys. 2013, 138, 244307. (27) Zhao, Y.; Wingen, L. M.; Perraud, V.; Greaves, J.; Finlayson-Pitts, B. J. Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air. Phys. Chem. Chem. Phys. 2015, 17, 12500–12514. (28) Sheps, L.; Scully, A. M.; Au, K. UV absorption probing of the conformer-dependent reactivity of a Criegee intermediate CH3CHOO. Phys. Chem. Chem. Phys. 2014, 16, 26701–26706. (29) Chhantyal-Pun, R.; Welz, O.; Savee, J. D.; Eskola, A. J.; Lee, E. P. F.; Blacker, L.; Hill, H. R.; Ashcroft, M.; Khan, M. A. H.; Lloyd-Jones, G. C., et al. Direct measurements of unimolecular and bimolecular reaction kinetics of the Criegee intermediate (CH3)2COO. J. Phys. Chem. A 2017, 121, 4–15. (30) Kumar, M.; Busch, D. H.; Subramaniam, B.; Thompson, W. H. Barrierless tautomerization of Criegee intermediates via acid catalysis. Phys. Chem. Chem. Phys. 2014, 16, 22968–22973. (31) Long, B.; Bao, J. L.; Truhlar, D. G. Atmospheric chemistry of Criegee intermediates: Unimolecular reactions and reactions with water. J. Am. Chem. Soc. 2016, 138, 14409–14422. (32) Anglada, J. M.; Gonzalez, J.; Torrent-Sucarrat, M. Effects of the substituents on the reactivity of carbonyl oxides. A theoretical study on the reaction of substituted carbonyl oxides with water. Phys. Chem. Chem. Phys. 2011, 13, 13034–13045. (33) Anglada, J. M.; Solé, A. Impact of the water dimer on the atmospheric reactivity of carbonyl oxides. Phys. Chem. Chem. Phys. 2016, 18, 17698–17712. (34) Chen, L.; Wang, W. L.; Wang, W. N.; Liu, Y. L.; Liu, F. Y.; Liu, N.; Wang, B. Z. Water-catalyzed decomposition of the simplest Criegee intermediate CH2OO. Theor. Chem. Acc. 2016, 135, 131. (35) Ryzhkov, A. B.; Ariya, P. A. A theoretical study of the reactions of parent and substituted Criegee intermediates with water and the water dimer. Phys. Chem. Chem. Phys. 2004, 6, 5042–5050. (36) Lin, L. C.; Chang, H. T.; Chang, C. H.; Chao, W.; Smith, M. C.; Chang, C. H.; Lin, J. J.; Takahashi, K. Competition between H2O and (H2O)2 reactions with CH2OO/CH3CHOO. Phys. Chem. Chem. Phys. 2016, 18, 4557–4568. (37) Long, B.; Tan, X. F.; Long, Z. W.; Wang, Y. B.; Ren, D. S.; Zhang, W. J. Theoretical studies on reactions of the stabilized H2COO with HO2 and the HO2···H2O complex. J. Phys. 16


Page 16 of 26

Page 17 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Chem. A 2011, 115, 6559–6567. (38) Kjaergaard, H. G.; Kurten, T.; Nielsen, L. B.; Jorgensen, S.; Wennberg, P. O. Criegee intermediates react with ozone. J. Phys. Chem. Lett. 2013, 4, 2525–2529. (39) Wei, W. M.; Yang, X.; Zheng, R. H.; Qin, Y. D.; Wu, Y. K.; Yang, F. Theoretical studies on the reactions of the simplest Criegee intermediate CH2OO with CH3CHO. Comput. Theor. Chem. 2015, 1074, 142–149. (40) Buras, Z. J.; Elsamra, R. M. I.; Jalan, A.; Middaugh, J. E.; Green, W. H. Direct kinetic measurements of reactions between the simplest Criegee intermediate CH2OO and alkenes. J. Phys. Chem. A 2014, 118, 1997–2006. (41) Hoops, M. D.; Ault, B. S. Matrix isolation study of the early intermediates in the ozonolysis of cyclopentene and cyclopentadiene: Observation of two Criegee intermediates. J. Am. Chem. Soc. 2009, 131, 2853–2863. (42) Jorgensen, S.; Gross, A. Theoretical investigation of the reaction between carbonyl oxides and ammonia. J. Phys. Chem. A 2009, 113, 10284–10290. (43) Long, B.; Cheng, J. R.; Tan, X. F.; Zhang, W. J. Theoretical study on the detailed reaction mechanisms of carbonyl oxide with formic acid. J. Mol. Struct. 2009, 916, 159–167. (44) Kurten, T.; Bonn, B.; Vehkamaki, H.; Kulmala, M. Computational study of the reaction between biogenic stabilized Criegee intermediates and sulfuric acid. J. Phys. Chem. A 2007, 111, 3394–3401. (45) Wei, W. M.; Zheng, R. H.; Pan, Y. L.; Wu, Y. K.; Yang, F.; Hong, S. Ozone dissociation to oxygen affected by Criegee intermediate. J. Phys. Chem. A 2014, 118, 1644–1650. (46) He, M. X.; Cao, H. J.; Sun, Y. H.; Han, D. D.; Hu, J. T. Mechanistic and kinetic study of the gas-phase reaction of vinyl acetate with ozone. Atmos. Environ. 2012, 49, 197–205. (47) Liu, F.; Beames, J. M.; Petit, A. S.; McCoy, A. B.; Lester, M. I. Infrared-driven unimolecular reaction of CH3CHOO Criegee intermediates to OH radical products. Science 2014, 345, 1596–1598. (48) Kettner, M.; Karton, A.; McKinley, A. J.; Wild, D. A. The CH3CHOO ‘Criegee intermediate’ and its anion: Isomers, infrared spectra, and W3-F12 energetics. Chem. Phys. Lett. 2015, 621, 193–198. (49) Kumar, M.; Busch, D. H.; Subramaniam, B.; Thompson, W. H. Criegee intermediate reaction with CO: Mechanism, barriers, conformer-dependence, and implications for ozonolysis chemistry. J. Phys. Chem. A 2014, 118, 1887–1894. (50) Osborn, D. L.; Taatjes, C. A. The physical chemistry of Criegee intermediates in the gas phase. Int. Rev. Phys. Chem. 2015, 34, 309–360. (51) Vereecken, L.; Francisco, J. S. Theoretical studies of atmospheric reaction mechanisms in the troposphere. Chem. Soc. Rev. 2012, 41, 6259–6293. (52) Vereecken, L.; Glowacki, D. R.; Pilling, M. J. Theoretical chemical kinetics in tropospheric chemistry: Methodologies and applications. Chem. Rev. 2015, 115, 4063–4114. (53) Mauldin III, R. L.; Berndt, T.; Sipilä, M.; Paasonen, P.; Petäjä, T.; Kim, S.; Kurtén, T.; Stratmann, F.; Kerminen, V. M.; Kulmala, M. A new atmospherically relevant oxidant of sulphur dioxide. Nature 2012, 488, 193–196. (54) Berndt, T.; Jokinen, T.; Mauldin, R. L.; Petaja, T.; Herrmann, H.; Junninen, H.; Paasonen, P.; Worsnop, D. R.; Sipila, M. Gas-phase ozonolysis of selected olefins: The yield of stabilized Criegee intermediate and the reactivity toward SO2. J. Phys. Chem. Lett. 2012, 3, 2898–2896. (55) Presto, A. A.; Donahue, N. M. Ozonolysis fragment quenching by nitrate formation: The pressure dependence of prompt OH radical formation. J. Phys. Chem. A 2004, 108, 9096–9104. (56) Cabezas, C.; Guillemin, J. C.; Endo, Y. Fourier-transform microwave spectroscopy of a halogen substituted Criegee intermediate ClCHOO. J. Chem. Phys. 2016, 145, 184304. 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(57) Aplincourt, P.; Ruiz-López, M. F. Theoretical investigation of reaction mechanisms for carboxylic acid formation in the atmosphere. J. Am. Chem. Soc. 2000, 122, 8990−8997. (58) Cremer, D.; Kraka, E.; Szalay, P. G. Decomposition modes of dioxirane, methyldioxirane and dimethyldioxirane — a CCSD(T), MR-AQCC and DFT investigation. Chem. Phys. Lett. 1998, 292, 97−109. (59) Gonzalez, C.; Schlegel, H. B. An improved algorithm for reaction path following. J. Chem. Phys. 1989, 90, 2154–2161. (60) Gonzalez, C.; Schlegel, H. B. Reaction path following in mass-weighted internal coordinates. J. Phys. Chem. 1990, 94, 5523–5527. (61) Boys, S. F.; Bernardi, F. The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors. Mol. Phys. 1970, 19, 553–566. (62) Bader, R. F. W. Atoms in molecules: A quantum theory. Oxford University Press: Oxford, UK, 1990. (63) Johnson, E. R.; Keinan, S.; Mori-Sánchez, P.; Contreras-García, J.; Cohen, A. J.; Yang, W. Revealing noncovalent interactions. J. Am. Chem. Soc. 2010, 132, 6498−6506. (64) Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comp. Chem. 2012, 2012 33, 580−592. (65) Canneaux, S.; Bohr, F.; Henon, E. KiSThelP: A program to predict thermodynamic properties and rate constants from quantum chemistry results. J. Comput. Chem. 2014, 35, 82–93. (66) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A., et al. Gaussian 09, Revision D.01; Gaussian, Inc.: Wallingford, CT, 2013. (67) Stone, D.; Blitz, M.; Daubney, L.; Howes, N. U. M.; Seakins, P. Kinetics of CH2OO reactions with SO2, NO2, NO, H2O and CH3CHO as a function of pressure. Phys. Chem. Chem. Phys. 2014, 16, 1139–1149. (68) Chao, W.; Hsieh, J.; Chang, C.; Lin, J. J. Direct kinetic measurement of the reaction of the simplest Criegee intermediate with water vapor. Science 2015, 347, 751–754. (69) Lewis, T. R.; Blitz, M. A.; Heard, D. E.; Seakins, P. W. Direct evidence for a substantive reaction between the Criegee intermediate, CH2OO, and the water vapour dimer. Phys. Chem. Chem. Phys. 2015, 17, 4859–4863.

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Scheme 1. Ozonolysis of alkenes to produce the carbonyl compound and Criegee intermediates, where R represents any alkyl substituent or halogen atom.

Scheme 2. Schematic diagram for the CIs + CH4 reaction channels, where R represents any alkyl substituent or halogen atom.

Figure 1. Optimized pre-reactive complexes (IM), transition states (TS), and products (P) in the pathways A (top) and B (bottom) for the reaction of CH2OO with CH4. The selected interatomic distances are given in Å. 19



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Figure 2. The changes of the potential energy along with the reaction coordinates of pathway A, where the selected geometry is given.

Figure 3. The changes of the selected bond along with the reaction coordinates in pathway A. 20


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Figure 4. The changes of the potential energy along with the reaction coordinates of pathway B, where the selected geometry is given.

Figure 5. The changes of the selected bond along with the reaction coordinates in pathway B. 21



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Figure 6. The reaction profiles for the available pathways in the reaction between CH2OO and CH4. The symbols R and P refer to the isolated reactants and products, respectively.

Figure 7. Calculated energy barriers and the enthalpy and free energy changes of the reactions between CIs and CH4. 22


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Figure 8. The energy barriers of pathway A as a function of the electron density at the BCP of the O-O bond of CIs.

Figure 9. The dependence of the rate constant (top) and tunneling corrections χ (bottom) versus temperature ranging from 200.0 to 1200.0 K for the pathway A. 23



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Table 1. The energy barriers (∆E*), relative energies (∆E), and the changes of the enthalpy and Gibbs free energy (∆H and ∆G) in the different reactionsa Reactions

∆E*

∆E

∆H

∆G

CH2OO+CH4 22.6/25.4 -82.0/-45.7 -82.0/-46.8 -83.9/-37.2 anti-CH3CHOO+CH4 20.6/24.5 -82.5/-42.5 -82.7/-43.6 -84.8/-33.5 syn-CH3CHOO+CH4 24.1/30.9 -79.0/-38.3 -79.1/-39.3 -81.4/-29.2 (CH3)2COO+CH4 23.2/30.3 -78.2/-35.5 -78.3/-36.6 -81.1/-25.9 anti-BrCHOO+CH4 15.0/21.9 -92.8/-49.7 -93.2/-50.7 -95.2/-40.9 syn-BrCHOO+CH4 19.4/28.5 -90.0/-50.0 -90.2/-51.0 -92.4/-40.9 anti-ClCHOO+CH4 14.6/22.4 -93.8/-48.6 -94.2/-49.7 -96.2/-39.8 syn-ClCHOO+CH4 18.9/28.9 -91.4/-49.4 -91.5/-50.5 -93.6/-40.3 anti-FCHOO+CH4 10.1/20.9 -100.2/-50.0 -100.5/-51.1 -102.4/-41.4 syn-FCHOO+CH4 13.5/24.3 -99.4/-51.9 -99.6/-52.9 -101.6/-42.9 6.5/17.3 -108.6/-64.2 -109.0/-65.3 -110.9/-54.9 F2COO+CH4 CH2OO+C2H6 16.5/23.0 -88.8/-48.4 -88.5/-49.0 -89.8/-38.7 CH2OO+C3H8(1°) 16.3/22.4 -88.5/-48.9 -88.1/-49.3 -88.3/-38.0 CH2OO+C3H8(2°) 14.2/20.6 -92.8/-50.7 -92.4/-51.2 -92.4/-39.5 CH2OO+C4H10(1°) 16.2/22.0 -88.5/-49.1 -88.1/-49.5 -88.3/-38.2 CH2OO+C4H10(2°) 14.4/20.2 -92.4/-50.6 -92.0/-51.0 -92.0/-39.4 CH2OO+isopentane(1°) 15.3/21.2 -88.4/-46.6 -87.9/-47.1 -88.1/-35.3 CH2OO+isopentane(1°′) 15.4/21.4 -88.5/-49.2 -88.1/-49.4 -88.3/-38.3 CH2OO+isopentane(1°′′) 16.0/22.3 -88.4/-49.3 -88.0/-49.7 -88.1/-38.3 13.0/19.1 -92.6/-50.3 -92.3/-50.8 -92.0/-38.3 CH2OO+isopentane(2°) CH2OO+isopentane(3°) 11.0/22.0 -95.8/-52.7 -95.4/-53.0 -95.0/-41.3 CH2OO+cyclopropane 16.9/16.2 -89.9/-52.0 -89.4/-52.5 -89.4/-40.8 CH2OO+cyclobutane 14.8/19.5 -94.0/-52.5 -93.6/-52.8 -94.3/-42.2 CH2OO+cyclopentane 12.7/18.4 -93.3/-51.5 -92.9/-52.0 -92.6/-39.2 CH2OO+cyclohexane 12.6/19.3 -93.0/-52.0 -92.6/-52.3 -93.5/-41.7 a All the data are in kcal/mol. The data before and after the slash refer to the results of the pathway A and pathway B, respectively. All the results have been obtained at the CCSD(T)/AUG-cc-pVTZ and CCSD(T)/AUG-cc-pVDZ levels of theory for the reactions involving CH4 and other reactions, respectively. The relevant thermodynamic corrections at the B3LYP/6-311++G(d,p) level of theory have been included. 1°, 2°, and 3° refer to the reaction between CH2OO and the primary, secondary, and tertiary C-H bonds of alkanes.

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Table 2. The reaction rate constant for the studied reactions at 298.15 Ka Reactions

Pathway A

Pathway B

CH2OO+CH4 5.09 × 10-32 5.68 × 10-29 -27 anti-CH3CHOO+CH4 2.14 × 10 1.39 × 10-31 syn-CH3CHOO+CH4 2.65 × 10-36 7.52 × 10-30 (CH3)2COO+CH4 2.54 × 10-29 6.40 × 10-36 -23 anti-BrCHOO+CH4 3.64 × 10 8.54 × 10-30 syn-BrCHOO+CH4 1.20 × 10-26 1.10 × 10-34 anti-ClCHOO+CH4 5.60 × 10-23 3.97 × 10-30 syn-ClCHOO+CH4 8.19 × 10-35 6.27 × 10-26 -20 anti-FCHOO+CH4 7.79 × 10 6.22 × 10-29 syn-FCHOO+CH4 2.24 × 10-22 1.20 × 10-31 F2COO+CH4 4.46 × 10-17 9.27 × 10-27 -25 CH2OO+C2H6 8.61 × 10-32 7.13 × 10 CH2OO+C3H8(1°) 2.83 × 10-30 8.66× 10-25 CH2OO+C3H8(2°) 4.45 × 10-25 1.10 × 10-29 CH2OO+C4H10(1°) 1.17 × 10-24 5.01 × 10-30 -23 CH2OO+C4H10(2°) 1.09 × 10 3.05 × 10-29 CH2OO+isopentane(1°) 5.54 × 10-25 1.37 × 10-30 CH2OO+isopentane(1°′) 1.35 × 10-30 4.84 × 10-25 CH2OO+isopentane(1°′′) 2.01 × 10-25 3.25 × 10-31 -23 CH2OO+isopentane(2°) 2.29 × 10 2.38 × 10-29 CH2OO+isopentane(3°) 2.14 × 10-31 9.58 × 10-22 CH2OO+cyclopropane 2.26 × 10-25 1.74 × 10-26 -23 CH2OO+cyclobutane 2.41 × 10-28 1.56 × 10 CH2OO+cyclopentane 2.21 × 10-28 2.40 × 10-22 CH2OO+cyclohexane 1.59 × 10-29 5.66 × 10-22 a All the data are in cm3 molecule-1 s-1. All the results have been obtained at the CCSD(T)/AUG-cc-pVTZ and CCSD(T)/AUG-cc-pVDZ levels of theory for the reactions involving CH4 and other reactions, respectively. 1°, 2°, and 3° refer to the reactions between CH2OO and the primary, secondary, and tertiary C-H bonds of alkanes.

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TOC Graphic

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Insights into the Reaction Mechanism of Criegee Intermediate CH2OO

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