Ozone depletion with the OH radical


> 
> $\ce{OH\*}$ radicals are known to deplete the ozone layer. Fill out the gaps below to complete the propagation stage:
> \begin{align}
>  \ce{? + O3 &-> ? + O2}\\
>  \ce{? + O3 &-> ? + O2}
> \end{align}
> 
> 
> 


So I am an A-Level chemistry student in the UK. We have covered ozone depletion in the context of free radical substitution with examples as follows:
\begin{align}
 \ce{ClCH3 &->[\text{U.V.}] Cl\* + \*CH3}\\
 \ce{Cl\* + O3 &-> ClO\* + O2}\\
 \ce{ClO\* + O &-> Cl\* + O2}
\end{align}


I know that we need the overall equation $\ce{O3 + O -> 2O2}$. However, all the examples covered in class have been of the form: \begin{align}
 \ce{X + O3 &-> Y + O2}\\
 \ce{Y + O &-> X + O2}
\end{align}


Clearly, the question provided at the top does not follow this form. We have never seen depletion reactions of the form $\ce{? + O3, ? + O3}$. Some internet research has lead to the idea that:


$$\ce{HO2, HO3, H2O3}$$


Are all chemicals that can occur in these atmospheric reactions. We have not studied any of them, but my best guess for an answer to the question is:


\begin{align}
 \ce{\*OH + O3 &-> HO2\* + O2}\\
 \ce{HO2\* + O3 &-> HO3\* + O2}
\end{align}


Is this right?




Another likely correct answer that obeys the constraints of the equation:



> 
> $\ce{X + O3 → Y + O2}$
> 
> 
> 


and forms likely stable radicals (as opposed to your suggested answer noting this reference ["On the stability of the elusive HO3 radical"](https://pubs.rsc.org/en/content/articlelanding/2011/cp/c1cp20791a)) for two members of the chain associated with an ozone depletion cycle which results in the net reaction:



> 
> $\ce{2 O3 → 3 O2}$
> 
> 
> 


is namely, the HOx ozone depletion cycle, where I claim that x may assume, at least functionally, the values of 0 and 1 as to oxygen presence. That is, possible acceptable answers could be $\ce{.H}$ and $\ce{.HO}$.


Support, per a source citing the HOx chain with x=1, namely: $\ce{.HO}$ [discussed briefly here](http://www.cchem.berkeley.edu/molsim/teaching/fall2008/ozone/Ozone%20website_files/Page749.htm), presents the reaction chain for $\ce{.OH}$ as:



> 
> $\ce{.HO + O3 → .HO2 + O2}$
> 
> 
> 



> 
> $\ce{.HO2 + O → .HO + O2}$
> 
> 
> 


And, by extension for x=0 (no oxygen, just hydrogen):



> 
> $\ce{.H + O3 → .HO + O2}$
> 
> 
> 


Source: ["Theoretical study of the H + O3 ↔ OH + O2 ↔ O + HO2 system"](https://aip.scitation.org/doi/10.1063/1.450342) where to quote:



> 
> The key features of the H+O3 potential energy surface are expected to be transferable to the X+O3 systems where X=Cl, OH, NO, and NH2.
> 
> 
> 


And the associated next step reaction:



> 
> $\ce{.HO + O → .H + O2}$
> 
> 
> 


Source: ["O + OH → O2 + H : A key reaction for interstellar chemistry. New theoretical results and comparison with experiment"](https://aip.scitation.org/doi/10.1063/1.3274226).


which completes the cycling of $\ce{.H}$ as required.


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