|This revised paper addresses most (but not all) of the comments of the other two reviewers and a few of my comments, but the responses to several of my comments were unsatisfactory. These are discussed below.|
In one of my comments, I stated that the abstract should say they used a simple chemical mechanism to describe the experiments, rather than a "modeling tool". Rather than address it, the author chose to criticize my comments and apparently misunderstood this rather obvious point. A "modeling tool" is just a software and/or algorithm, and doesn't describe any chemistry. It is the chemical mechanism implemented in the tool that describes what is happening, and it could be employed using any number of modeling tools. The author seems to think that I don't know the difference between a modeling tool and a mechanism, but after over 40 years working in this field I suspect the problem is more likely with him.
A comment I made regarding the apparent formation of acetaldehyde in the O3 + 2BOL reaction, was also not satisfactorily addressed. Figure 2 shows acetaldehyde coming from the OH-substituted Criegee, but doesn't show a co-product or suggest a mechanism, since its formation is not expected based on what is known of simpler Criegees. I gave a suggested mechanism but I incorrectly wrote "formaldehyde" when I should have written "formyl radicals" (ultimately giving acetaldehyde + CO + HO2 + OH). The authors correctly noted my error, but apparently didn't bother to look at the system and see that the co-product should obviously be formyl. Their main response was that the main point is that acetaldehyde is probably formed from this Criegee (or so the data suggest), but speculation on the mechanism was beyond the scope of the paper. This is a fair point, but in this case, they should not pretend it is a mechanism on Figure 2, but instead should show a "?" and "+ other products" as I suggested in my comment.
I also commented on their statement that there was curvature in Figure 4 in the yield plots for 2HPr, but this was not evident in the figure. In response, the author stated that there was curvature for individual experiments, but this is not evident in Figure 4 because it shows all the experiments with a single symbol. Since this curvature is noted in the text, the readers should be able to see it for themselves. Either use different symbols for different experiments in Figure 4 or, if this doesn't show this clearly, then show a plot of a representative experiment as an insert or in a supplement.
With regard my proposed mechanism for forming formaldehyde from the PAN analogue shown on Figure 7, the author criticized my suggesting about what I called a "1,4-H" shift of the PAN analogue, stating it was really a 1,5-H shift, which is less favorable (but not always). But this suggested reaction actually has a 6-member ring transition state, so can't be criticized on this basis. However, there is no need for the authors to accept this suggestion because it does not affect the results of interest, though the possibility of another route for acetaldehyde formation would be of interest in the context of this figure.