# Predicting the products of reaction between ammonia and hydrogen peroxide

Like we do in organic chemistry is there any way to write the mechanism of the reaction between $\ce{NH_3}$ and $\ce{H_2O_2}$?

Can the products be predicted?

• Please don't introduce mathjax code to question titles due to the searchability issues that rise. – M.A.R. Dec 7 '15 at 21:23
• @Ϻ.Λ.Ʀ. Oh sorry.I'm so acquainted with that in math SE that I forget it sometimes.Thanks for reminding @M.A.R! – user14857 Dec 7 '15 at 21:24

Strong solutions of $\ce{H2O2}$ with a few drops of $\ce{NH4OH}$ (aq. ammonia) is left for 24 hours without any nitrite formation occurring. But upon longer standing, even with a small amount of hydroxide then nitrite forms. Nitrite also forms when a dilute solution of $\ce{H2O2}$ is mixed with $\ce{NH4OH}$ and is evaporated over pure conc. $\ce{H2SO4}$ with a bell jar. $\ce{H2O2}$ forms (even in very dilute solutions) nitrite very rapidly, if the $\ce{H2O2}$ solution is mixed with a few drops of $\ce{NH4OH}$ and a little $\ce{NaOH}$ and this then boiled in a retort to a very small volume.

$\ce{2NO2- + 2H+(aq) <=> H2O + NO + NO2}$

$\ce{NO2- + NO3- + 2H+(aq) <=> H2O + NO2}$

Nitrogen dioxide is then able to attack ammonia.

$\ce{2NO2 + 2NO + 4NH3 -> 2NH4NO2 + 2H2O + 2N2~~~~~~~~~~~~~~~~~~~~(1)}$

In any case, solutions of ammonium nitrite decompose on heating to 60 to 70C.

Perhaps the very slow spontaneous reaction of aqueous ammonia with $\ce{H2O2}$ takes place the small equilibrium with amide anions, $\ce{NH2-}$.

$\ce{NH2- + H2O2 -> NH2- + 2OH-}$

Even in $\ce{NH4OH}$, there is a very slight equilibrium with amide ions.

$\ce{2NH3 <=> NH2- + NH4+}$

Amide rapidly and vigorously reacts with water, so the equilibrium of amide existence in water must be very low.

$\ce{NH2-+ H2O -> NH3 + OH-}$

In the base catalysed decomposition of hydrogen peroxide, the mechanisms is presumably:-

$\ce{H2O2 + OH- -> HOO- + H2O}$

$\ce{HOO- + H2O2 -> HOOOH + OH-}$

$\ce{HOOOH --> HOOO- + H+(aq)}$

$\ce{HOOO- -> OH- + O2}$

Also, ammonium nitrite decomposes into nitrogen and water.

$\ce{NH4NO2 → N2 + 2 H2O~~~~~~~~~~~~~~~~~~~~~~~~~~(2)}$

A combination of ammonia and hydrogen peroxide is often used in the process of bleaching hair. Hydrogen peroxide has the necessary properties to remove the color from hair - it oxidizes one of hair’s melanin pigments to a colorless substance. This results in the hair becoming lighter. However, it is not recommended by hair professionals (those who don't understand chemistry but want your cash), and can cause extensive damage to hair (even causing it to fall out).

Therefore, the overall reaction is:-

$\ce{2(NH3•H2O) + 3H2O2 ->[\Delta] N2 + 8H2O~~~~~~~~~~~~~~~~~~~~~~~(1) + (2)}$

As far as I can tell, the prior answer while posting several well known reactions, did not actually detail how nitrite is introduced.

To be honest, this is not an easy question to answer and as far as I know, even the pundits have not agreed on the precise pathway. I suspect the actually kinetics starts with the action of light on an alkaline solution introducing the hydroxyl radical and possible solvated electrons:

OH-(aq) + hv --> •OH + e-(aq) (see ‘Flash photolysis in the vacuum ultraviolet region of sulfate, carbonate, and hydroxyl ions in aqueous solutions’ by Elie Hayon, and John J. McGarvey, in J. Phys. Chem., 1967, 71 (5), pp 1472–1477, DOI: 10.1021/j100864a044 , link: https://pubs.acs.org/doi/abs/10.1021/j100864a044?journalCode=jpchax )

This could be followed by some radical reactions:

NH3 + •OH --> •NH2 + H2O (See Eq (1) at "Kinetics and Mechanism of the Reaction of •NH2 with O2 in Aqueous Solutions", by B. Laszlo , Z. B. Alfassi , P. Neta , and R. E. Huie, J. Phys. Chem. A, 1998, 102 (44), pp 8498–8504, DOI: 10.1021/jp981529+, July 15, 1998, at https://ws680.nist.gov/publication/get_pdf.cfm?pub_id=831494 )

•NH2 + O2 --> •NH2O2 (Same source, Eq(2))

O2 + e-(aq) --> •O2- (Same source, Eq(3))

•NH2O2 + •O2- --> O2 + NH2O2- (Same source, Eq(7))

And also, some standard chemical reactions:

NH2O2- --> NO- + H2O (Same source, Eq(8))

NO- + H2O2 = NO2- + H2O (Speculation, as NO- with O2 (not H2O2) forms peroxynitrite, but NO2- + H2O2 --> peroxynitrite, see http://www.jbc.org/content/289/51/35570.full.pdf, so NO- + 2 H2O2 = (NO2- + H2O2) + H2O = aqueous peroxynitrite is a supportive argument for the speculated reaction as it suggests a consistent reaction system!)

NH4+ + NO2- = NH4NO2 .

The source of oxygen above follows from the instability of alkaline H2O2 to self-decompose through various pathways or from the presence of air in an open vessel. If dust (which can contain transition metals like iron,..) is allowed to enter the solution, a possible Fenton (or Fenton-like with Cu, Mn,..) reaction could proceed producing a source of hydroxyl radical (in place of the action of light) although this suggested path would be hindered by the addition of OH-, so not my preferred likely explanation.