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Anders Hoveland

NH3 + H2O2

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What I am most interested in is what can oxidize NH3 to oxides of nitrogen at room temperature. Supposedly, hydrogen peroxide will react with ammonia in the presence of a catalyst, but there seems to be virtually no information about this in the literature. (whether the catalyst is iron salts or acetamide?)

 

What exactly is the chemistry between H2O2 and NH4OH ? Does acetone serve as a necessary catalyst for the reaction? When the two are mixed, there is no observable reaction, and there are many references in the literature to mixes of the two chemicals, presumably without reaction.

 

Under what conditions can ammonia be oxidized to NH4NO2 ? Excess H2O2 would presumably oxidize the NH4NO2 to NH4NO3. Nitrite is a much more reactive reducing agent than ammonia, so to obtain any nitrite one would think that a large excess of ammonia would have to be used.

 

Hydogen peroxide slowly decomposes in aqueous alkaline solution, so one would expect NH4OH/H2O2 solutions to gradually decompose, either with the liberation of oxygen, or possibly the oxidation of ammonia.

 

A mixture of hydrogen peroxide and ammonium hydroxide (in a 1:3 ratio) acts as a reactive oxidizer, which can attack organic compounds and elemental carbon. The reaction rate is negligible at room temperature, but when heated to 60°C the reaction becomes vigorous and self-sustaining. Such solutions are sometimes known as "base piranha". With a 1:1:5 volume ratio of NH4OH, H2O2, and H2O, respectively, the half-life times of peroxide were 4 hours at 50°C and 40 minutes at 80°C. "Reaction of Ozone and H2O2 in NH4OH Solutions and Their Reaction with Silicon Wafers" Japanese Journal Applied Physics. 43 (2004) pp. 3335-3339.

 

Strong solutions of H2O2 with a few drops of NH4OH or solutions of ammonium carbonate (with or without NaOH or Na2CO3) can be let to stand 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 H2O2 is mixed with NH4OH and a little Na2CO3 and is evaporated over pure conc. H2SO4 with a bell jar. H2O2 forms (even in very dilute solutions) nitrite very rapidly, if the H2O2 solution is mixed with a few drops of NH4OH and a little NaOH or Na2CO3, and this then boiled in a retort to a very small volume. They suggest this nitrite formation as a demonstration experiment because it is very quick to do, and then after acidification of the colorless liquid with H2SO4, the HNO2 can be nicely be proven to be present. Hoppe-Seyler

 

 

"A process developed by Produits Chimiques Ugine Kuhlmana (PcUK), and practiced by Atofina (France) and Mitsubish Gas (Japan) involves the oxidation of ammonia by hydogen peroxide in the presence of butanone (MEK) and another component that apparently serves as an oxygen-transfer agent. The reaction is carried out... at at 50degC. The ratio of H2O2/MEK:NH3 used is 1:2:4. Hydrogen peroxide is activated by acetamide and disodium hydrogen phosphate (117). The mechanism of this reaction involves an activation of the ammonia and hydrogen peroxide because these compounds do not themselves react (118-121). It appears that acetamide functions as an oxygen transfer agent, possibly as the iminoperacetic acid, HOOC(=NH)CH3, which then oxidizes the transient Schiff base formed between MEK and ammonia to give give the oxaziridine, with regeneration of acetamide."

 

(117) U.S. Pat. 3,962,878 (aug. 3, 1976), J.P. Schirmann, J. Combroux, and S. Y. Delavarenne

(118) J.P. Schirmann and S. Y. Delavarenne, Tetrahedtron :ett. 635 (1972)

(119) E. G. E. Hawkins, J. Chem. Soc. C, 2663 (1969)

(120) E. Schmitz, Chem. Ber. 97, 2521 (1964)

(121) Can. Pat. 2,017,458 (Nov. 24, 1990), J.P. Schirmann, J. P. Pleuvry, and P. Tellier (to Atochem)

 

D. Todd, in R. Adams, ed.,Organic Reactions, Vol. 4, John Wiley & Sons, Inc., New York, 1948, Chapt. 8. "Hydrazine and its Derivitives"

 

If I can now be allowed to speculate a little into the reaction.

 

So it appears that H2O2 can much more readily attack imines, R2C=NH, than it can plain ammonia? I thought I came across a book that stated that there is no reaction between H2O2 and imines without the use of some acetamide, which serves as a catalyst.

 

One wonders why nitrite forms rather than nitrate, since the H2O2 should readily oxidize the nitrite. One possibility may be that nitrite is initially the predominant product, but as nitrate begins to be formed, it alters the equilibrium, allowing formation of more nitrogen dioxide rather than nitric oxide.

 

(2) NO2[-] + (2) H[+]aq <==> H2O + NO + NO2

NO2[-] + NO3[-] + (2) H[+]aq <==> H2O + (2)NO2

 

Nitrogen dioxide is known to be able to attack ammonia.

 

(2)NO2 + (2)NO + (4)NH3 --> (2)NH4NO2 + (2)H2O + (2)N2

 

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

 

Perhaps the very slow spontaneous reaction of aqueous ammonia with H2O2 takes place the small equilibrium with amide anions, NH2[-].

 

NH2[-] + H2O2 --> NH2* + OH* + OH[-]

 

Even in NH4OH, there is a very slight equilibrium with amide ions.

 

(2)NH3 <==> NH2[-] + NH4[+]

 

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

 

H2O2 + OH[-] --> HOO[-] + H2O

HOO[-] + H2O2 --> HOOOH + OH[-]

HOOOH --> HOOO[-] + H[+]aq

HOOO[-] --> OH[-] + O2

 

Is the dihydrogen trioxide intermediate reactive enough to oxidize ammonia? H2O3, also known as "trioxone" quickly decomposes into water and singlet [excited] oxygen. The reaction is actually reversible, but much less favorable.

 

(2)H2O + O2* <==> H2O + H2O3

 

One question I would have though is what the dominant reaction in the spontaneous decomposition of NH4OH-H2O2 solutions. Is the reaction mainly the base catalysed decomposition of H2O2 into O2 ? Or is the main reaction the formation of ammonium nitrite? What proportion of the final product contains ammonium nitrate rather than nitrite?

 

And why does the reaction proceed so much faster when heated? Relative to the energy required to break most chemical bonds, the boiling point of the solution is not really much hoter than room temperature. Why would this make so much difference?

 

 

 

An interesting reaction from the literature of Marcellin Berthelot, dry ammonia gas reacts with the nitrogen dioxide and nitric oxide, at room temperature,

 

(2)NO2 + (2)NO + (4)NH3 --> (2)NH4NO2 + (2)H2O + (2)N2

 

Solid ammonium nitrite inside a tube explodes if heated on a water bath to between 60-70degC. And the substance gradually decomposes at room temperature, slower if cold, or faster in aqueous solutions, forming nitrogen gas.

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After a quick read of this post, there is one thing I see that sticks out. I can't see [ce] NH_{2}^{-} [/ce] ions having any significant existence in aqueous solution. They would be protonated extremely fast.

 

Can you find an equilibrium constant for the amide ion getting protonated in water?

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After a quick read of this post, there is one thing I see that sticks out. I can't see [ce] NH_{2}^{-} [/ce] ions having any significant existence in aqueous solution. They would be protonated extremely fast.

 

Can you find an equilibrium constant for the amide ion getting protonated in water?

 

No doubt the existence of amide ions is EXTREMELY unfavorable in ammonium hydroxide. The equilibrium would be very very small, virtually negligable for most reaction kinetics.

 

But the room temperature, uncatalysed reaction between ammonium hydroxide and hydrogen peroxide is also very slow. There is no observable reaction products after 24 hours. It takes several days before enough ammonium nitrite is created to be detectable. The very slow reaction rate is not incongruent with an amide reaction mechanism explanation.

 

The reaction between pressurised liquid anhydrous NH3 and pure H2O2 would likely proceed at a much faster rate.

 

As for amide getting protonated in water, I do not know the exact equilibrium constant, but I do know that sodium amide rapidly and vigorously reacts with water, so the equilibrium of amide existence in water must be very low.

 

NH2[-] + H2O --> NH3 + OH[-]

Edited by Anders Hoveland

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What exactly is the chemistry between H2O2 and NH4OH ? Does acetone serve as a necessary catalyst for the reaction? When the two are mixed, there is no observable reaction, and there are many references in the literature to mixes of the two chemicals, presumably without reaction.

 

I would be cautious of adding acetone to a solution containing H2O2 as you may end up with acetone peroxides, which are incredibly nasty and explosive.

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