[levis123]

I tried to reduce dinitro compound to diamine using iron and ammonium chloride in water/methanol. After the end of the reaction I evaporated methanol followed by workup of aqueous solution, then I was left with a solid with a much different melting point than I was expecting (60 C off). I have read that diamines often are sensitive to air oxidation, and maybe this is the reason i dont have my product. I am not sure how to overcome this problem.

The IR spectrum shows fery faint N-H peaks, but also seems to be dangerously similar to my starting material, which is however insoluble in water and should precipitate if there is any, but my solution is clear.

Any suggestions? I must use iron because I dont have access to any other catalyst.

[rolnor]

I would monitore the reaction with TLC, Rf should go down. Its a heterogenous reaction so it depends on stirring how fast it is. Its sounds as if its not finished.

[hollytara]

I agree with Rolnor - let it go longer.  These reductions aren't as easy as they are described. 

[levis123]

I agree with Rolnor - let it go longer.  These reductions aren't as easy as they are described.

I let it run for 21 hours in reflux. TLC showed formation of product.

[levis123]

I would monitore the reaction with TLC, Rf should go down. Its a heterogenous reaction so it depends on stirring how fast it is. Its sounds as if its not finished.

Iron sticks to the magnet and hinders the stirring - maybe that was the problem?

[rolnor]

I have used iron/80% acetic acid, the reaction is ready after 30minutes.

[OrganicDan96]

hydrogenation with raney Ni works well for reducing nitro groups to amines

[kriggy]

Pd/C + H2 is my go-to system for nitro group reduction quite fast as well most of the time. What is the nitro group positions? Maybe there is some side reaction occuring? ALso, Im not sure but doestn Fe + NH4Cl goes to hydroxylamine instead?

[levis123]

I have used iron/80% acetic acid, the reaction is ready after 30minutes.

Ok, maybe I'll try Fe in acetic acid or HCl. Thank you 

[levis123]

Pd/C + H2 is my go-to system for nitro group reduction quite fast as well most of the time. What is the nitro group positions? Maybe there is some side reaction occuring? ALso, Im not sure but doestn Fe + NH4Cl goes to hydroxylamine instead?

The nitro groups are meta- to each other. I also have a carboxylic acid on the ring at meta- position to both of those. The paper I'm following claims a NO2 to NH2 conversion in these conditions.

[wildfyr]

Sometimes diazonium salts get made when reducing nitros and these like to turn into oligomeric tar. Other times they make diazobenzene compounds in small yield that are brightly colored. These side products are incomplete reduction products.

I've tried a LOT of "mild" nitro to amine reductions from the lit and most of them worked poorly or not at all in my hands. YMMV.

The Fe/acid one is known as a Bechamp reduction. I think there's a variation with Zn that avoids the stir bar attraction. Otherwise I would mechanical stir, the iron won't mix well stuck to the bar.

[rolnor]

Pd/C + H2 is my go-to system for nitro group reduction quite fast as well most of the time. What is the nitro group positions? Maybe there is some side reaction occuring? ALso, Im not sure but doestn Fe + NH4Cl goes to hydroxylamine instead?

The nitro groups are meta- to each other. I also have a carboxylic acid on the ring at meta- position to both of those. The paper I'm following claims a NO2 to NH2 conversion in these conditions.

Are you following an exact reaction as in the paper? You get an amino acid and it could be water in the product maybe?

[levis123]

Sometimes diazonium salts get made when reducing nitros and these like to turn into oligomeric tar. Other times they make diazobenzene compounds in small yield that are brightly colored. These side products are incomplete reduction products.

I've tried a LOT of "mild" nitro to amine reductions from the lit and most of them worked poorly or not at all in my hands. YMMV.

The Fe/acid one is known as a Bechamp reduction. I think there's a variation with Zn that avoids the stir bar attraction. Otherwise I would mechanical stir, the iron won't mix well stuck to the bar.

Thank you, I didn't know about this. If Fe does not work I will try to use Zn. I am just not sure whether the conditions are too mild for a dinitro to diamino conversion.

[levis123]

Pd/C + H2 is my go-to system for nitro group reduction quite fast as well most of the time. What is the nitro group positions? Maybe there is some side reaction occuring? ALso, Im not sure but doestn Fe + NH4Cl goes to hydroxylamine instead?

The nitro groups are meta- to each other. I also have a carboxylic acid on the ring at meta- position to both of those. The paper I'm following claims a NO2 to NH2 conversion in these conditions.

Are you following an exact reaction as in the paper? You get an amino acid and it could be water in the product maybe?

The paper has a -Br instead of -COOH at the same position. But how can I avoid the formation of amino acid?

[rolnor]

Pd/C + H2 is my go-to system for nitro group reduction quite fast as well most of the time. What is the nitro group positions? Maybe there is some side reaction occuring? ALso, Im not sure but doestn Fe + NH4Cl goes to hydroxylamine instead?

The nitro groups are meta- to each other. I also have a carboxylic acid on the ring at meta- position to both of those. The paper I'm following claims a NO2 to NH2 conversion in these conditions.

Are you following an exact reaction as in the paper? You get an amino acid and it could be water in the product maybe?

The paper has a -Br instead of -COOH at the same position. But how can I avoid the formation of amino acid?

Thats a big difference, the compound you are trying to make is a amino acid and you must think of this when you do the workup, its water soluble both under basic and acidic
conditions. I think in this case Pd/C hydrogenation is better to avoid getting water soluble by-products.