# Why doesn't nitric oxide react with water?

Why doesn't $\ce{NO}$ (nitric oxide) react with water? I know it is a neutral oxide, but I'm really curious as to why that is. Why will $\ce{NO}$ not react with $\ce{H2O}$?

• Why would it? Normally we explain why things happen, and not why they don't. – Ivan Neretin Mar 22 '17 at 22:31
• Think about it, oxides dissolve in water to give their corresponding acids or bases. Here, what acid would you get, and how stable would its conjugate base ? i believe now you have your answer – SubZero Mar 23 '17 at 7:26
• @IvanNeretin what is "normal"? – ParaH2 Mar 23 '17 at 8:22

Although nitric oxide is thermodynamically unstable, it is kinetically stable as its decomposition rate is very slow[ref] and so it is considered stable and won't normally react to anything.

So, nitric oxide wouldn't normally hydrolyze easily. But in the presence of air, it forms nitrous acid $(\ce{HONO})$:

$$\ce{4NO + O2 + 2 H2O -> 4 HNO2}$$

However, nitrous acid is very unstable and quickly disproportionates:

\begin{align} \ce{2 HNO2 &-> NO2 + NO + H2O &(cold dil. soln.)}\\ \ce{3 HNO2 &-> HNO3 + 2 NO + H2O &(warm conc. soln.)} \end{align}

Since $\ce{HNO2}$ is required to prepare diazonium salts (a versatile compound in organic chemistry), it is prepared in-situ by reaction of $\ce{NaNO2}$ and $\ce{HCl}$. Due to its instability, it is prepared for one-time use and is not stored for further preparations.

Reference: J. Phys. Chem., 1958, 62 (3), pp 360–361 https://doi.org/10.1021/j150561a030

I have also heard about a disproportion reaction which happens with a productivity of around $0,01 \%$ as,

$$\ce{4NO + H2O -> N2O + 2HNO2}$$

• Hi thanks for your contribution. Though in such cases, it's much better to cite your source as well. A research paper or a famous textbook generally works. Thanks! – Gaurang Tandon Apr 24 '18 at 9:16
• My chemistry teacher, a professor at my university told me about this reaction a long long time ago. Since then the only source where I could find this reaction was a Russian website which also contains a vast database of known chemical reactions. There is no original source, there's a mistake (HNO3 instead of HNO2) and the only note is "almost no reaction". Sorry, it's a really interesting reaction and I keep wondering about its mechanism but I just fail to find any papers or books, at least on the Internet. – user63281 Apr 24 '18 at 23:03
• No worries, and I appreciate your response. But in this case, I think it's rather better if you instead ask a new question, looking for proper citation for the reaction. We support reference-request as well, so it wouldn't be a problem :-) – Gaurang Tandon Apr 25 '18 at 0:23