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the Creative Commons Attribution 4.0 License.
| 29 Jan 2026
Evaluated kinetic and photochemical data for atmospheric chemistry: Volume IX – gas phase reactions of halogenated alkanes, alkenes, and oxygenated compounds
Abstract. This article, the ninth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation. It covers an extension of the gas phase and photochemical reactions of halogenated alkanes, alkenes, and oxygenated organic compounds implemented on the IUPAC website since 2008. The article consists of a summary table of the recommended kinetic parameters for the evaluated reactions, and a supplement containing the data sheets providing information upon which the recommendations are made.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 12 Mar 2026)
- RC1: 'Comment on egusphere-2026-259', Anonymous Referee #1, 13 Feb 2026 reply
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RC2: 'Comment on egusphere-2026-259', Anonymous Referee #2, 17 Feb 2026
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(1). In Section 2.3, the reactions A + B + M → AB + M and AB + M → A + B + M are presented in the text. Assigning equation numbers to these reactions would increase the clarity. In other words, all equations need to carry equation numbers for clarity.
(2). If this study focuses on a series of halogenated oxygenated VOCs, why were esters not included in the selected compounds?
(3). In your previous work (Volume IV), theoretical data were referenced for branching ratio calculations of C3 molecules. In the present study, the system involves molecules larger than C3, yet no theoretical data are provided for the branching ratio. The authors may include these data for completion purposes.
Citation: https://doi.org/10.5194/egusphere-2026-259-RC2 -
RC3: 'Comment on egusphere-2026-259', Anonymous Referee #3, 18 Feb 2026
reply
1) General Comments
This manuscript presents the ninth volume of a series of IUPAC evaluations of atmospheric chemical kinetic and photochemical data. It provides updated and newly assessed gas‑phase and photochemical reactions for halogenated alkanes, alkenes, and oxygenated organic compounds, reflecting developments since the 2008 Volume IV publication. These kinds of evaluations/compilations are greatly appreciated not only for atmospheric chemists but also for policy makers and modelers. Thus, the article highlights the expanding environmental and regulatory relevance of halogenated species —particularly HFCs and their industrial replacements— and emphasizes the need for accurate kinetic data to support atmospheric modeling and policy.
The evaluation of kinetic data focuses mainly on OH reactions, but Cl, NO3 and O3 reactions are also included for some halogenated species. However, since the last evaluation in 2008, the literature on gas-phase reaction kinetic studies on halogenated species has notably increased. Despite that, new results have not been incorporated in the present evaluation, and it would be worth including them, in my opinion.
Regarding the photochemical data, this assessment is only focused on fluorinated aldehydes as these species (slightly) absorb in the solar actinic region. It is likely that iodine species can also present some UV absorption in that spectral region. In fact, UV absorption cross sections for the iodine species included in the kinetic data evaluation were already published (Roehl et al. 1997 Journal of Geophysical Research, 102, 12,819-12,829). Authors have to consider if it is worth including them or not.
Overall, the manuscript provides a highly valuable update of the kinetic and photochemical data that complements the interactive online IUPAC database.
2) Specific Comments on the manuscript
Unify “gas phase reactions” or “gas-phase reactions”. Generally, the second one is used.
Unify “high(or low)-pressure limit” or “high (or low) pressure limit”
Unify “cross-section” or “cross sections”
Some reactions in sections 2.2 and 2.3 are not numbered.
Although Section 3.2 is of great interest from the theoretical background point of view, maybe this section on the treatment of termolecular reactions could be shortened. Only two termolecular reactions are evaluated here: oFOx162 and oFOx163.
Line 621: Authors state that “Rate coefficients are also known as rate constants, both terms are used here”. Perhaps this statement should be placed at the beginning of the manuscript, if authors consider the use of both terms. I would prefer to unify it. In fact, “rate constant” is only used only in section 3.2.
3) Specific Comments on the Supplementary Information
Although I did not make a large scrutiny, I noticed that some reactions are not properly updated. Is there any reason for not including them? For example:
oFOx143: The evaluation of this reaction was made in June 2025 with the newest data from 2011. However, a more recent article was published (Blázquez et al. 2022, https://doi.org/10.1039/D2CP00160H).
oFOx149: The evaluation of the HO+sevoflurane reaction was made in September 2025 and a paper on published in June 2025 (Espinosa et al. 2025. https://doi.org/10.1039/D5EM00061K).
oFOx150: The HO+desflurane reaction was evaluated. What about isoflurane (CF3CHClOCHF2)? There are some papers on this reaction (see below).
I miss more recent results on some OH- and Cl-reactions which are not included in the evaluation. I am giving here some examples:
Halogenated alkanes
HO+CH3CHBrCH2CH3 (2025, https://doi.org/10.1039/d5cp00961h)
Halogenated alkenes
HO+CH2=CHCH2OCF2CHF2 (2024, https://doi.org/10.1007/s11356-024-35536-4)
HO+CF3(CF2)2CH=CH2 (HFC-1447fz) (2016, https://doi.org/10.1021/acs.est.5b04379)
HO+ CF3CH=CH2 (HFO‑1243zf) ( 2015, https://doi.org/10.1007/s11356-014-3426-2)
Cl+CH2=CHCH2OCF2CHF2 (2024, https://doi.org/10.1007/s11356-024-35536-4)
Cl+CxF2x+1CH=CH2(x=1-6) (2017, https://doi.org/10.1016/j.chemosphere.2016.09.156)
O3+CxF2x+1CH=CH2(x=1-6) (2018, https://doi.org/10.1016/j.chemosphere.2018.02.183)
Halogenated ethers
HO + CHF2CF2CH2OCH3 (HFE-374pcf), and CF3CF2CH2OCH3 (HFE-365mcf3): 2022, https://doi.org/10.1039/D2CP00160H.
HO+isoflurane (CF3CHClOCHF2): Latest 2011: https://doi.org/10.1021/jp2077598; 2025: https://doi.org/10.1039/D5EM00061K).
Revise the special characters and/or spelling of the last name of some authors. For example, Sellevag (instead of Sellevåg), Sulbæk (instead of Sulbaek), Antiñolo (instead of Antinolo) among others are misspelled in several ways and places.
Format of the plot in oFOx161 datasheet is not the same as the rest.
Page 234: Some absorption cross sections of n-C4F9CHO are negative. Can these values be substituted by ~0? Usually, a negative value means that there is no absorption at that wavelength. On the other hand, the presented absorption cross sections do not include uncertainties.
Page 232 and 239: Dashed lines in the figure are not visible in the legend.
4) Suggestions/ Typographical errors
Line 96: Change “If the temperature coefficient has been measured…” by “If the temperature dependence of the rate coefficient…”
Line 98: Change “…the normal Arrhenius form” by “the conventional Arrhenius form”
Line 99: Replace E by Ea (activation energy) to avoid any confusion with E parameter in k= E T2exp(-F/T). I suggest using Ea/R instead of E/R throughout the paper.
Line 120: Please, delete “spectroscopy” from CIMS – chemical ionization mass spectroscopy/spectrometry. It is not an spectroscopic technique.
Line 408: The next table lists the preferred absorption cross section data and the preferred quantum yields at appropriate wavelength intervals. What table?
Line 425: I0 is defined as the incident light intensity, however it should be defined as the transmitted light intensity in the absence of absorber. Experimentally, the incident light intensity can be higher than the transmitted light intensity in the absence of absorber.
Citation: https://doi.org/10.5194/egusphere-2026-259-RC3 -
RC4: 'Comment on egusphere-2026-259', Anonymous Referee #4, 20 Feb 2026
reply
This kinetic and photochemical data evaluation is important and timely. Some of my comments overlap with those of other reviewers, so I won't repeat them here. I only have a few questions and suggestions in addition to what has already been said.
For the perfluorinated acids - Hurley 2004 reported for n=2-4, k(OH + F(CF2)nCOOH)) has a rate coefficient of (1.69 ( 0.22) x 10-13 cm3 molecule-1 s-1 at 296 K. I wonder why two k296 values were listed in the evaluation for the same technique, neither of them the reported value, and then a preferred value of 1.5 x 10-13 cm3 molecule-1 s-1 was chosen.
When evaluating the OH reaction with photolabile molecules such as CHF2CHO (PF5), the authors should also comment on how, or if, a correction for photolysis at the wavelengths used to generate OH radicals in experiments (e.g., 248 nm and 310 nm in oFOx97) has been made and how that infers their preferred values.
Citation: https://doi.org/10.5194/egusphere-2026-259-RC4
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This manuscript constitutes Volume IX of the series Evaluated kinetic and photochemical data for atmospheric chemistry. The authors present data sheets in Volume IX for the gas-phase and photochemical reactions of halogenated organic species that have been added since the publication of Volume IV. It covers the extension of the gas-phase and photochemical reactions of halogenated alkanes, alkenes, and oxygenated organic compounds, as implemented on the IUPAC website since 2008. This is excellent work that will be very useful for modelers and experimental kineticists.
The manuscript consists of a summary table of the recommended kinetic parameters for the evaluated reactions and a supplement containing the data sheets that provide the information on which the recommendations are based. This structure is well designed: the overall organization is clear, and the data presentation is intuitive, allowing readers to efficiently search for and compare kinetic and photochemical parameters across different reaction systems. I recommend publication after the authors address the following minor comments.
1. The data sheet table in the Supporting Information (Pages 2-4) currently lacks page numbers for reactions, which may hinder data navigation. It is recommended that the authors add this information.
2. On Page 94 of the Supporting Information, there is a typo in the unit of the reported rate coefficient (cm3 molecule-1 s-).