AndersHoveland
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NO + O2 intermediate?
Does anyone know what the intermediate(s) are when nitric oxide reacts with diatomic oxygen (at room temperature)? What are the reaction mechanisms?
As anyone who knows about kinetic theory knows, it is exceedingly unlikely that any three molecules will simultaneously react with eachother. Nearly
all reactions involve two molecules first reacting with eachother to form an intermediate.
In the case of one molecule of NO and one molecule of O2, any intermediate molecule or molecules that forms would be highly reactive.
There seems to be only two possible pathways:
Two molecules of nitric oxide can transiently dimerize into N2O2, which could then be oxidized with with a molecule of O2, presumably forming an
intermediate square ring. The ring would then immediately break apart into two molecules of NO2.
One molecule of NO could be directly oxidized by a O2 to form a nitrate radical NO3•, which would then eventually react with another molecule of NO.
somewhere in the literature (if remember correctly) it stated that the reaction proceeds through both pathways, but that the first predominates, which
would explain the relatively slow reaction rate. but if even a small part of the reaction proceeds through the second path, could not the nitrate
radical be used as a powerful oxidizer for some third regent?
For example, if sulfur dioxide was also introduced into the reaction at the same time?
[Edited on 15-9-2011 by AndersHoveland]
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woelen
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What do you mean with 'relatively slow'. In my experience the reaction is very fast. Contact between NO and O2 immediately leads to formation of brown
NO2. I tried this in the following experiment:
http://woelen.homescience.net/science/chem/exps/NO_O2/index....
Mixing the NO with SO2 before adding O2 indeed could lead to interesting things. Maybe some SO3 is formed (NO + O2 --> NO3; NO3 + SO2 --> NO2 +
SO3). This would require special glassware though, because any water should be avoided in that case. Maybe there is someone who can make a dry and
constant flow of NO and SO2 and mix these gases before air is allowed to reach that gas mix?
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AndersHoveland
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This is just complete speculative imagination, but possible reactions might be:
O2 + SO2 + (2)NO --> (NO)2SO4
(4)O2 + (4)SO2 + (6)NO --> (2) (NO)2S2O7 + (2)NO2
(2)O2 + (2)SO2 + (2)NO --> (NO)S2O7(NO2)
The oxygen and sulfur dioxide should probably be pre-mixed and used in a large excess, then a much smaller portion of nitric oxide should be very
slowly and gradually added. In any case, the oxidation of SO2, if it occurs to any extent, is likely to be very inefficient. Care should be taken to
avoid the presence of any moisture, otherwise any oxidation products that might form would hydrolyse to sulfuric acid.
[Edited on 16-9-2011 by AndersHoveland]
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497
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There is a scanned book around here somewhere called "Absorption of Nitrous Gasses" that goes through a lot of this in great detail.
As concentration of NO drops the oxidation to NO2 does begin to proceed slowly. To get 99% conversion can take minutes. The first 70-80% reacts within
seconds though.
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hkparker
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This is the book, from the library:
http://library.sciencemadness.org/library/books/absorption_o...
My YouTube Channel
"Nothing is too wonderful to be true if it be consistent with the laws of nature." -Michael Faraday
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AndersHoveland
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This may be a revealing article:
http://pubs.acs.org/doi/abs/10.1021/es60093a015
They reacted NaCl, NO2, SO2, and air together, and obtained some interesting results.
"Formation of nitrosyl chloride from salt particles in air"
William H. Schroeder, Paul Urone
Environ. Sci. Technol., 1974, 8 (8), pp 756–758
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