[Miep]

Hi,

Could someone tell me about the mechanism when reducing a nitro group with Fe/HCl?  I found a mechanism based on single electron transfer, however isn't there H2 formed as a reductor?

Thanks,
Miep

[movies]

I believe the mechanism you found with SET is probably correct.  You might generate a small amount of H₂, but these reactions are not run under an atmosphere of hydrogen like in other metal reductions, so the hydrogen is probably just lost to the atmosphere.

Also remember that H₂ doesn't act as the direct reductant in catalytic hydrogenation – it is likely a metal hydride or a hydrogen radical that does the reaction.  These intermediates are also possible in nitro reduction, I suppose, but I don't know all the evidence for why the SET mechanism is preferred.