Oligomerization Reactions of Criegee Intermediates with 1 Hydroxyalkyl Hydroperoxides : Mechanism , Kinetics , and 2 Structure-Reactivity Relationship

Structure-Reactivity Relationship 3 Long Chen, 1,2 Yu Huang, * ,1,2 Yonggang Xue, 1,2 Zhenxing Shen, 3 Junji Cao, * ,1,2 Wenliang Wang 4 4 1 Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese 5 Academy of Sciences, Xi’an, Shaanxi, 710061, China 6 2 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth 7 Environment, Chinese Academy of Sciences, Xi’an 710061, China 8 3 Department of Environmental Sciences and Engineering, Xi'an Jiaotong University, 9 Xi'an, 710049, China 10 4 School of Chemistry and Chemical Engineering, Key Laboratory for 11 Macromolecular Science of Shaanxi Province, Shaanxi Normal University, Xi'an, 12 Shaanxi, 710119, China 13


Introduction
Alkenes are the most abundant volatile organic compounds (VOCs) in the atmosphere after methane and primarily originate from anthropogenic and biogenic sources (Lester et al., 2018).Gas-phase ozonolysis of volatile alkenes is extremely exothermic, and the potential energy surface (PES) following the 1,3-cycloaddition of ozone to the C=C double bond forming a primary ozonide (POZ) is riddled with shallow wells and low barriers (Donahue et al., 2011;Aplincourt et al., 2000), which then dissociate to produce a carbonyl oxide (also called Criegee intermediates (CIs)) and a carbonyl moiety (Johnson et al., 2008;Welz et al., 2012;Criegee, 1975).Alkene ozonolysis is thought to be an important source of radicals, whose subsequent reactions lead to the formation of hydroperoxides, organic peroxides, and secondary organic aerosols (SOAs) (Donahue et al., 2011;Becker et al., 1990;Kroll et al., 2008;Hallquist et al., 2009;Tobias et al., 2001), and thus influence air quality, climate forcing and human health (Rissanen et al., 2014;Donahue et al., 2011;2012).Criegee intermediates were first proposed by Rudolph Criegee as early as 1975 (Criegee, 1975), and their direct synthesis in the laboratory experiment were performed by the photolysis of organic iodides in the presence of O 2 and the photolytic Cl-initiated oxidation of dimethyl sulfoxide (DMSO) (Welz et al., 2012;Taatjes et al., 2008).
Experimentally, Su et al. (2013) investigated the transient infrared absorption spectrum of CH 2 OO using a step-scan Fourier-transform spectrometer, and observed that the vibrational frequencies are more consistent with a zwitterion rather than a diradical structure.Taatjes et al. (2013) studied the kinetics of CH 3 CHOO reactions with H 2 O, SO 2 , and NO 2 , and found that anti-CH 3 CHOO is substantially more reactive toward water and SO 2 than is syn-CH 3 CHOO with an upper limit rate coefficient (1.0 ± 0.4) × 10 -14 cm 3 molecule -1 s -1 .Also Smith et al. (2015) reached similar conclusions in their UV absorption of the CH 2 OO + H 2 O reaction system that the rate coefficient is determined as (7.4 ± 0.6) × 10 -12 cm 3 molecule -1 s -1 at 298 K, and it exhibits a large negative T-dependence at temperatures from 283 to 324 K.
Moreover, oligomerization reactions of CIs with typical atmospheric species are identified as one of the dominate pathways leading to the formation of highly oxygenated and high-molecular-weight oligomers that have remarkably low vapor pressure contributing to SOAs formation and growth (Bonn et al., 2008;Heaton et al 2007;Wang et al., 2016;Inomata et al., 2014).For example, Sakamoto et al. (2013) performed laboratory-scale ethylene ozonolysis in a Teflon bag reactor, and revealed that the sequential addition of CH 2 OO to hydroperoxides leads to oligomeric hydroperoxides and finally affords SOAs.Sadezky et al. (2008) proposed that SOAs formation is initiated by the reaction of SCI with a RO 2 radical, followed by the sequential addition of SCIs, and chain termination by reaction with HO 2 radical.Also several groups reached similar conclusions that the highly oxygenated molecules (HOM) are produced via RO 2 autoxidation in the cyclohexene and terpenes ozonolysis systems (Rissanen et al., 2014;Kirkby et al., 2016;Berndt et al., 2018).
Moreover, HOM are major contributors to aerosol particle formation and growth on a global scale (Tröstl et al., 2016;Stolzenburg et al., 2018) (Wang et al., 2016).Moreover, oligomerization reactions accompany with the shorter time period during the early stage of SOAs growth (Heaton et al., 2007).
Therefore, we think that it is essential to investigate the Criegee chemistry-based mechanism of SOAs formation and growth.molecules• cm -3 ) under atmospheric conditions (Zhang et al., 2014;Zhang et al., 2015), the reaction with water vapour is the dominant chemical sink (Aplincourt et al., 2000).
Also Ryzhkov et al. (2003;2004;2006) (Vereecken et al., 2012;Anglada et al., 2013), and revealed that the above reaction initially proceeds via the formation of a strong pre-reactive complex followed by a submerged electronic-energy barrier for the subsequent addition of the CH 3 OO terminal oxygen atom to the CH 2 OO central carbon atom.An analogous conclusion was obtained by investigating the reactions of anti-CH 3 CHOO with HO 2 and H 2 O 2 molecules, i.e., the sequential addition of SCIs is a favorable reaction mode for SOAs formation (Chen et al., 2017).Vereecken et al. (2017)  In this study, we mainly focus on the oligomerization reaction of carbonyl oxides with HHPs leading to the formation of high-molecular-weight oligomers under atmospheric conditions.This reaction represent the initial step of oligomer formation and growth during alkene ozonolysis, and therefore need to be extensively characterized to gain deeper insights into the fundamental chemical composition of these oligomers in the atmosphere.Moreover, structure-reactivity relationship plays an important role in determining the rates and outcomes of bimolecular processes.
Herein, we employ high-level theoretical calculations in conjunction with kinetics analysis to study the mechanism and kinetics of the reactions of four carbonyl oxides with four HHPs, and describe the effects of carbonyl oxide conformation on reaction rate.The carbonyl oxides considered in this work (CH 2 OO, syn-/anti-CH 3 CHOO, and (CH 3 ) 2 COO) are anticipated upon ozonolysis of ethylene, propylene, isobutene and 2,3-dimethyl-2-butene, while the investigated HHPs are assumed to arise from bimolecular reactions with water vapour in the troposphere.

Computational details
The geometries of all stationary points on PES are optimized and characterized by the M06-2X functional (Zhao et al., 2006) in combination with the 6-311+G(2df,2p) basis set (Zheng et al., 2009), since the M06-2X functional allows one to reliably compute the energies and stability of non-covalent interactions (Zhao et al., 2008a,b).Harmonic vibrational frequencies are performed at the same level of theory to verify that the nature of each structure is either a minimum (NIMAG = 0) or a transition state (NIMAG = 1) and to provide the zero point vibrational energy (ZPVE) corrections.A scale factor of 0.98 is applied to scale all the M06-2X/6-311+G(2df,2p) frequencies to account for the thermodynamic contribution to the Gibbs free energy and enthalpy at 298 K and 1 atm (Zheng et al., 2009).The reactant-product connectivity on either side is established by intrinsic reaction coordinate (IRC) calculations (Fukui, 1981).

Bimolecular reaction of SCIs with water vapour
Equations ( 5) and ( 6) represent the two types of bimolecular reactions between carbonyl oxides and water vapour.Previous investigations have shown that some carbonyl oxides are largely removed by their reactions with water dimer (Chen et al., 2016a,b;Chao et al., 2015;Taatjes et al., 2013;Anglada et al., 2016 ) to generate HHPs (Chen et al., 2016a,b;Anglada et al., 2011), which are important atmospheric oxidants initiating vegetation damage (Becker et al., 1990).Further mechanistic details of the above reaction can be found in our previous works (Chen et al., 2016a,b;2018).
Figure 1 presents a simplified scheme for the reactions of several distinct carbonyl oxides (CH 2 OO, syn-/anti-CH 3 CHOO, (CH 3 ) 2 COO) with water dimer to form HHPs. In all cases, each reaction begins with the formation of a strong pre-reactive complex and then surmounts a small barrier that is still lower in energy than the reactants before product generation.Table 1 contains the relative energies of stationary points and the activation energies of elementary reactions.In Figure 1 and Table 1, labels A, B, C, and D correspond to the relative energies of the pre-reactive complex (RC), transition state (TS), post-reactive complex (PC) and the product (P).
R1 and R2 denote syn-and anti-positions of the substituent, respectively.These four transition states are located by rotation of two dihedral angles (DO2H4O4H3, DO4H2O3H1).Based on the energies given in Table 1, products Pa and Pb are near-isoenergetic conformers differing only in the orientation of the H1 atom along the C1-O3 bond.As has been mentioned above, HHPs are key reactive intermediates that possess with -OH and -OOH functional groups, and can therefore sequentially react with carbonyl oxide to generate oligomers.Considering the fact that Pa and Pb are structurally and energetically similar, the former is judiciously selected for studying oligomerization reactions, whereas the latter is merely listed in the Figures S1-S3.2016), which makes its chemistry particular important for forest and urban environments.The largest sink of CH 2 OO corresponds to its bimolecular reaction with water dimer in the troposphere, which generates HO-CH 2 OO-H as the dominant product (Lewis et al., 2015;Kumar et al., 2014).Figure 2 shows the schematic PES for the reaction of CH 2 OO with HO-CH 2 OO-H, with the optimized geometries of all stationary points on this PES given in Figure S4.

PES for the reaction of CH
Figure 2 shows that the differences between the relative free energies and the electronic energies for all stationary points are significant (~ 10-24 kcal• mol -1 ), implying that the addition reactions of the parent carbonyl oxide with Pa 1 are characterized by obvious contributions of entropy effect.Similar behaviors are also observed for oligomerization reactions of other carbonyl oxides with HHPs (see Figures 3-5).Thus, unless otherwise stated, the discussion in the following sections refers to free-energy barriers (ΔG a # ).
The formation of oligomers P2a, P2b, P2c and P2d (containing CH 2 OO as the repeating unit) is strongly exothermic (>104 kcal• mol -1 ), and the apparent activation energies E app observed for all elementary reactions are negative values, signifying that these reactions are both thermochemically and dynamically feasible under The secondary addition reaction CH 2 OO + P1a is equivalent to that of CH 2 OO + Pa 1 reaction, and hence features an analogous pathway, i.e., the formation of pre-reactive complexes IM2a and IM2b in entrance channels, is followed by the addition of -OH and -OOH groups of P1a to the CH 2 OO central carbon atom to produce P2a and P2b.The barrier heights predict TS2a and TS2b to lie -36.3 and -35.9 kcal• mol -1 , respectively, below the energies of the separate reactants, and 7.5 and 7.4 kcal• mol -1 above the energies of the corresponding pre-reactive complexes IM2a and IM2b.The above result shows that these two addition reactions (R2a and R2b) equally contribute to the title reaction system.Compared to the first CH 2 OO addition reaction, the second one features a lower barrier.Finally, the addition reaction CH 2 OO + P1b proceeds via mechanism fairly similar to those described above for the CH 2 OO + P1a system and do not discussing in detail to avoid redundancy.

PES for the reaction of CH 3 CHOO with HO-CH 3 CHOO-H
The methyl-substituted parent Criegee intermediate can exist in two conformations, syn-and anti-CH 3 CHOO, depending on whether the methyl group is located on the same or opposite side of the terminal oxygen (Yin et al., 2017).
Numerous theoretical studies have proven that the presence of an intramolecular hydrogen bond in the syn-conformer makes it more stable than the anti-conformer (Anglada et al., 2011;2016).The interconversion of these two conformers via rotation around the C-O bond has a very high barrier (~ 42 kcal• mol -1 ), which implies that one can treat syn-and anti-CH 3 CHOO as independent species existing in the atmosphere (Yin et al., 2017).It is well known that the predominant pathway of unimolecular reaction of syn-CH 3 CHOO is isomerization to vinyl hydroperoxide (VHP) via the hydrogen atom transfer, whereas the preferable route of unimolecular reaction of anti-CH 3 CHOO is ring-closure to dioxirane via an oxygen atom transfer (Donahue et al., 2011;Taatjes et al., 2013;Long et al., 2016).Both of the prompt and thermal unimolecular decay of the energized VHP may dissociate to OH radicals, and their yields are strongly pressure and temperature dependents (Kroll et al., 2011a,b).The dioxirane can finally isomerize to acetic acid via the "hot acid" channel (Kroll et al., 2011a,b).Long et al. (2016) proposed that the enthalpic barrier of syn-CH 3 CHOO isomerization to VHP is more than ~3 kcal higher than that of the addition reaction syn-CH 3 CHOO + H 2 O, indicating that the latter reaction is the dominant pathway.

PES for the reaction of (CH 3 ) 2 COO with HO-(CH 3 ) 2 COO-H
The dimethyl-substituted Criegee intermediate (CH 3 ) 2 COO is generated in the ozonolysis of 2,3-dimethyl-2-butene (Lester et al., 2018;Drozd et al., 2017).The unimolecular reaction of (CH 3 ) 2 COO and its bimolecular reaction with water vapour strongly depend on temperature (Long et al., 2018).For example, the unimolecular reaction is the dominant decay pathway above 240 K, whereas it reaction with SO 2 can compete well with the corresponding unimolecular reaction below 240 K (Long et al., 2018).Although a fraction of (CH 3 ) 2 COO may proceed unimolecular decomposition or react with SO 2 under some specific conditions, the removal of this species from the atmosphere mainly occurs via its reaction with water vapour due to its higher atmospheric concentration (Kuwata et al., 2015;Long et al., 2018;Huang et al., 2015), which afford HO-C(CH 3 ) 2 OO-H as the major product.The PES of addition reactions (CH 3 ) 2 COO + HO-C(CH 3 ) 2 OO-H is given in Figure 4, and the optimized geometries of all stationary points are shown in Figure S7.
As shown in Figure 4, the vdW complexes IM7a and IM7b are 5.0 and 5.1 kcal• mol -1 lower in energy than the reactants, while the corresponding transition states TS7a and TS7b leading to products P7a and P7b are 10.3 and 14.2 kcal• mol -1 higher in energy than the respective complexes.The formation of P7a and P7b is strongly exothermic, with the reaction energies of -31.0 and -25.8 kcal• mol -1 .Again, this result shows that the addition of the -OOH group in Pa 3 to the central carbon atom of (CH 3 ) 2 COO is both thermochemically and dynamically favorable.Compared with the barriers of 2anti-CH 3 CHOO + Pa 2 system given in Figure 3(a), one can notice that the dimethyl-substituted parent carbonyl oxide leads to the barrier increasing by ~ 5 kcal• mol -1 .The secondary addition reaction (CH 3 ) 2 COO + P7a is found to be similar to that described for the (CH 3 ) 2 COO + Pa 3 system.The pre-reactive complexes IM8a and IM8b are formed in entrance channels with over 5.0 kcal• mol -1 stabilization energies, and followed by the addition of -OH and -OOH groups in P7a to the central carbon atom of (CH 3 ) 2 COO to generate P8a and P8b.According to the predicted barrier heights, TS8a and TS8b lie 12.0 and 13.0 kcal• mol -1 above complexes IM8a and IM8b, respectively, which shows that the second addition reactions R8a and R8b are nearly equally accessible.

PES of distinct SCI reactions with HO-CH 2 OO-H
To gain deeper insights into the substituent-influenced modification atmospheric oligomer composition, one should elucidate the origin of the substituent influence on the reactivity and kinetics of carbonyl oxides.Therefore, an understanding of structure-reactivity relationships is important for determining bimolecular processes and reaction products.Since the addition of the -OOH group to the central carbon atom of SCIs is shown to be both thermochemically and dynamically preferable, this type of addition reaction is selected to study the effect of substituents on the reactivity of carbonyl oxides.The PES of addition reactions SCIs + HO-CH 2 OO-H is given in As shown in Figure 5, each reaction begins with the formation of a strong pre-reactive complex and then surmounts a medium barrier that is higher in energy relative to the reactants before forming the corresponding products.The bimolecular reaction of CH 2 OO with HO-CH 2 OO-H to form P1a(HO-(CH 2 OO) 2 -H) is characterized by a barrier of 8.8 kcal• mol -1 and an exothermicity of 43.4 kcal• mol -1 .
Hence, the small barrier and large stability of the hydroperoxide species imply that its formation is both thermochemically and kinetically favoured.Notably, the introduction of a methyl group at the anti-position reduces the barrier by ~ 1.0 kcal• mol -1 relative to that of the CH 2 OO + HO-CH 2 OO-H system, whereas the corresponding syn-and dimethyl substitutions increase the above barrier by 4. conformers in the atmosphere.A similar conclusion has been obtained by studying the reactions of syn-/anti-CH 3 CHOO with water and SO 2 , i.e., the rate coefficient of the anti-CH 3 CHOO reaction was calculated to be one to two orders of magnitude higher than that of the syn-CH 3 CHOO system (Lin et al., 2016;Huang et al., 2015;Taatjes et al., 2013;Anglada et al., 2016).Therefore, it is concluded that the position and number of methyl groups significantly affect barrier heights and reaction rates.On the other hand, the exothermicities of other reaction pathways are lower than that of the parent system, which implies that methyl substitution is thermochemically unfavorable.A similar trend is observed for the bimolecular reactions of SCIs with other HHPs (Figures S8-S10).In order to avoid redundancy, we do not repeat them here in detail.

Kinetics and implications in atmospheric chemistry
To better understand the effect of substituents on reaction kinetics, the rate coefficients of distinct SCI reactions with HO-CH 2 OO-H are computed using a combination of canonical transition state theory and Eckart tunneling correction at temperatures between 273 and 400 K, with the obtained results listed in Table 2.
Table 2 shows that the predicted rate coefficients for the reaction of CH 2 OO with HO-CH 2 OO-H(R1a) decrease with increasing temperature, with a similar trend observed for syn-CH 3 CHOO(R9), anti-CH 3 CHOO(R10), and (CH 3 ) 2 COO + HO-CH 2 OO-H(R11) systems.The above behavior is ascribed to the fact that the apparent activation barriers E app of these four addition reactions are significantly negative, as previously observed for the reaction of CH 3 O 2 with BrO (Shallcross et al., 2015).These findings imply that a significant fraction of atmospheric carbonyl oxides may survive under high temperature conditions and react with peroxy radical or organic acid to generate SOAs.
The obtained data shows that the rate coefficient depends on the relative position and number of methyl groups in the parent carbonyl oxide, e.g., the rate coefficient increases by two orders of magnitude when methyl substitution occurs at the anti-position, whereas a reduction by four orders of magnitude is observed for methyl reactive than the parent carbonyl oxide and the syn-conformer (Anglada et al., 2011;2016).On the other hand, the introduction of two methyl groups does not result in a marked rate coefficient change compared to the parent system, since the addition reaction R11 is mediated by the pre-reactive hydrogen-bonded complex.
As discussed above, the reaction of anti-CH 3 CHOO with HO-CH 2 OO-H is preferred over the other three pathways.Therefore, it would be interesting to investigate whether the reaction between anti-CH 3 CHOO and HO-CH 2 OO-H can compete with the reaction between anti-CH 3 CHOO and formic acid, which represents a substantially dominant atmospheric degradation pathway (Welz et al., 2014).
Therefore, the anti-CH 3 CHOO + HO-CH 2 OO-H reaction may not compete with the anti-CH 3 CHOO + HCOOH reaction during daytime.However, the concentration of formic acid dramatically decreases in the nighttime, allowing the anti-CH 3 CHOO + HO-CH 2 OO-H reaction to compete with the anti-CH 3 CHOO + HCOOH reaction at temperatures below 273 K when the concentration of HCOOH equals 9.0 × 10 7 molecules cm -3 .(d) The rate coefficients show a significant increase when adding a methyl group on the anti-position, whereas it displays a dramatical decrease on the syn-position.

Conclusion
On the other hand, the addition of dimethyl group does not cause much variation in the rate coefficients.
Zhao et al. (2015) studied the ozonolysis of trans-3-hexene in a flow reactor and static chambers in the absence and presence of an OH or SCI scavenger at 295 ± 1 K, arriving at the same conclusion as above.In particular, oligomers having SCIs as chain units were identified as one of the dominant components of atmospheric SOAs and were produced by the sequential addition of C 2 H 5 CHOO to RO 2 radical.More recently,Wang et al. (2016) investigated the heterogeneous ozonolysis of oleic acid (OL) using an aerosol flow tube, and found that reactions of particulate SCIs generate high-molecular-weight oligomers, with low volatility that are preferentially partitioned into the particle phase to promote SOAs formation.They confirmed that the SCI-based mechanism is dominant pathway in the formation of high-molecular-weight oligomers.On the other hand,Ehn et al. (2014) reported a large source of low-volatility SOAs generated from the ozonolysis of α-pinene and other endocyclic monoterpenes under atmospheric conditions, and proposed that the mechanism of extremely low-volatility organic compounds (ELVOCs) formation is driven by RO 2 autoxidation.
atmospheric condition.Product Pa 1 (HO-CH 2 OO-H) formed in the reaction of CH 2 OO with water dimer has two functional groups (-OH and -OOH), both of which can be involved in addition reactions.The addition reactions of 2CH 2 OO + Pa 1 begin with the formation of loosely bound pre-reactive complexes IM1a and IM1b, of -3.5 and -3.1 kcal• mol -1 stability.They are formed by a hydrogen bond between the terminal CH 2 OO oxygen atom and the hydrogen atom of the -OOH group in Pa 1 , and a van der Waals (vdW) bond between the central carbon atom of CH 2 OO and the oxygen atom of the -OH group in Pa 1 .The above complexes are immediately converted into products P1a and P1b via transition states TS1a and TS1b with barriers of 8.8 and 12.2 kcal• mol -1 , respectively, while the corresponding reaction exothermicities are estimated as 43.4 and 40.5 kcal• mol -1 , respectively.The above result shows that the most favorable channel is the addition of the -OOH group of Pa 1 to the parent carbonyl oxide.The detailed mechanism mainly involves that the HO-CH 2 OO moiety Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2018-935Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 November 2018 c Author(s) 2018.CC BY 4.0 License.released from the breaking O-H bond in Pa 1 binds to the central carbon atom of CH 2 OO, and simultaneously the remnant hydrogen atom transfers to the terminal oxygen leading to product P1a.The addition pathway opens the door for other subsequent reactions leading to SOAs via Criegee chemistry, which may result in aerosol formation and thus impact climate.As pointed out in previous studies(Chen et al., 2016a,b;Kumar et al., 2014), the thermal unimolecular decay of Pa 1 can occur via two competitive pathways, namely (i) HO-CH 2 OO-H → CH 2 O + H 2 O 2 and (ii) HO-CH 2 OO-H → HCOOH + H 2 O.However, since the corresponding barriers are much higher than that of the bimolecular reaction with CH 2 OO (~35 kcal• mol -1 ), the thermal unimolecular decay of HHPs is not taken into consideration in this work.
suggest that water can effectively scavenge CH 3 CHOO to generate low volatile HO-C(CH 3 )HOO-H and thus promote SOAs formation.The energy diagram of addition reactions between CH 3 CHOO and HO-C(CH 3 )HOO-H is given in Figure 3.The optimized geometries of all stationary points are shown in Figures S5 and S6.

Figure 3
Figure 3(a) demonstrates that the sequential additions of anti-CH 3 CHOO to Pa 2 are strongly exothermic and spontaneous, indicating that the occurrence of these consecutive reactions in the atmosphere is thermochemically feasible.The addition reactions of 2anti-CH 3 CHOO + Pa 2 start with the barrierless formation of pre-reactive complexes IM3a and IM3b held together by weak hydrogen bonds and vdW forces.

Figure 5 ,
Figure 5, whereas those for bimolecular reactions with other HHPs are displayed in Figures S8-S10.
Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2018-935Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 November 2018 c Author(s) 2018.CC BY 4.0 License.substitution at the syn-position.Thus, the relative position of the methyl group plays an important role in determining SCI reactivity, in particular, anti-substitution promotes the reaction with HHPs and accelerates the formation of oligomers in the atmosphere.Anglada et al. arrived at the same conclusion by studying the reactions of SCIs with water vapour, showing that the anti-conformer is significantly more Atmos.Chem.Phys.Discuss., https://doi.org/10.5194/acp-2018-935Manuscript under review for journal Atmos.Chem.Phys.Discussion started: 6 November 2018 c Author(s) 2018.CC BY 4.0 License.The reactivity and kinetics of oligomerization reactions of Criegee intermediates with HHPs are studied using quantum-chemical methodologies in conjunction with statistical theory calculations.The main conclusions are summarized as follows: (a) The oligomerization reactions of SCIs with HHPs are strongly exothermic and spontaneous, signifying that the consecutive reactions are feasible thermochemically in the atmosphere.(b) The addition of -OOH group in HHPs to the central carbon atom of SCIs is both thermochemically and dynamically preferable as compared with the -OH group addition pathway.(c) The reaction barrier and kinetics strongly depend on both, the number of the substituents in the Criegee intermediate and on its position (syn-or anti-).