Synthesis and Characterization of Atmospherically Relevant Hydroxy Hydroperoxides
Round 1
Reviewer 1 Report
HOMs play important roles in NPF. The strength of this paper is the synthesis of biogenic peroxides - these compounds are needed for simulations of peroxide reactions (e.g., autoxidation) and calibration of HOMs in CIMS. The authors used several chemical analytical methods, NMR, FT-IR, UV-Vis analysis, and HrTOF-CIMS (nitrate and proton transfer). These combined methods help to verify the molecular structures of the synthesized compounds. I suggest the authors include detailed chemical reaction schemes involved in chemical synthesis.
I am a little surprised to see the extremely low sensitivity of nitrate-CIMS. This is almost 3 orders of magnitude lower than what we currently assume (that is, the same as the sulfuric acid sensitivity). Does this mean that the entire HOMs-CIMS community completely got wrong with HOMs all these years? There are many high-profile papers published from CLOUD studies and others, using sulfuric acid sensitivity. This is kind of disturbing to realize. Of course, this is not the authors' responsibility and on the contrary, if this study provides a valid sensitivity, this will be an important contribution to the community in this context. If this is the case, the authors should emphasize the implications of their new sensitivities.
I am more concerned with the method used here to measure HOMs with CIMS – that is, inject synthesized HOMs in the chamber and detect with CIMS. If this is the case, I understand that nucleation takes place rapidly and there are also wall losses. HOMs concentrations should be estimated from steady-state conditions, taking these loss processes into consideration.
Author Response
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Reviewer 2 Report
Review : Synthesis and Characterization of Atmospherically Relevant Hydroxy Hydroperoxides
This manuscript describes a synthesis for key low-NOx oxidation products of isoprene and alpha-pinene. While I believe the authors have shown they did indeed synthesize the compounds reported, there is insufficient comparison to previous characterization of ISOPOOH compounds. Some clear comparisons of peak positions and relative heights should be included.
The mass spectra in the PTR-MS and CI-MS should be shown.
It does not make sense that the ISOPOOH cross section is similar to methyl hydroperoxide, yet you calculate that ISOPOOH photolyzes 100 times faster. This calculation should be re-done and explained more thoroughly.
Why is the alpha-pinene hydroperoxide not detectable with CIMS while ISOPOOH is? The comment about clustering is not sufficient as written. Why would the clustering be so different despite the same functional group being present?
This manuscript could be acceptable for publication once clearer comparison with either previous NMR/FTIR/MS spectra or similar compounds (e.g. CH3OOH and tert-butyl hydroperoxide). Much of the analysis seems speculative and the broad conclusions (e.g. photolysis in tropical regions) seems too far of an application for the tentatively quantified properties (absorption cross section).
Author Response
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Reviewer 3 Report
The manuscript submitted by Hartmut Herrmann and coworkers is interesting. But the presentation should be improved and there are some typos and grammatical errors. Please check your article for this one more time. The manuscript should be revised to enhance the readability of the scientific results. Overall I recommend the publication of this manuscript in Atmosphere" after minor revision. Please put all spectra in supplementary materials.
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Round 2
Reviewer 3 Report
The authors correctly answered to the questions and the manuscript can be published in the present form.
Author Response
We thank the reviewer for his positive comments.
