OK, I don't know if this helps, but using google I found a paper yesterday which deals with the reductive amination of nitro compounds of the form 'R-NO
2' to their corresponding amines (Rode C. V., Vaidya M. J., Chaudhari R. V., 2001. Hydrogenation of nitrobenzene to aminophenol in four-phase reactor: reaction kinetic and mass transfer effect.Chem. Eng. Sci. 56 1299-1304).
(see also
http://www.tech.chem.ethz.ch/hungerb/research/reaction/hydrogenation.html
for details)
It seems to proceed via the hydroxylamine.
Here it is:
1. R-NO
2 + H
2 -> R-NO + H
2O (-135 kJ/mol)
2. R-NO + H
2 -> R-NHOH (-155kJ/mol)
3. R-NHOH + H
2 -> R-NH
2 + H
2O (-260kJ/mol)
alternatively, the following reaction may occur, leading back to step 2):
3b) 2 R-NHOH -> R-NO + R-NH
2 + H
2O (-55kJ/mol)
As you can see the reaction is kinda exothermic.
They also postulated the following formula:
R
H2 =
wk'[H2][RNO2] 1+K
B[RNO
2]
where
k'[(m
3*kg-1*s-1)(m
3*kg-1*mol-1*s-1)] = reaction rate constant
K
B [l*mol-1] = Adsorption equilibrium constants
R
A [kmol*m
3-1*s-1] = Overall rate of hydrogenation reaction
w [kg/m
3] = catalyst loading
Don't ask me anything about it, I just typed it for those of you who like theoretical chemistry/mathematics and for the sake of completeness, I don't understand ANYTHING besides that you could use it for calculating everything related to this reaction...
Oh, not to forget the catalytic hydrogenation (happening at the same time if, let's say, a nitropropene is being reduced):
Hydrogen and alkene are being adsorbed by the catalyst, one proton (H+) is being transferred to the carbon with the double bond (which one? a bond is always BETWEEN TWO carbons, I thought..
) and the p-bond is being replaced by two s-bonds (at least I think it works that way, the paper says nothing about it)
...but water? It MUST bee some other reaction that converts the ketone to its amine, obviously the above reaction is favoured by removing water from the RXN...
(Sorry Rhod, I know this is perhaps off-topic, but just didn't find the right thread, but it seemed to bee worth posting it... if it will be moved to a thread more related to nitropropene reductions, that's just fine)