Is there any possibility of reducing the water insoluble organic nitro compounds to its amine form. I was trying to reduce the 3-methyl-5-nitrobenzoic acid to 3-amino-5-methylbenzoic acid by using Sn/ HCl but reaction is not taking place.
Reduce water insoluble organic compounds by using Sn/ HCl , dissolve nitro compd. in minimum amount of acetic acis or ethanol , then add tin powder and Conc.HCl and reflux gently for 2 hrs. , cool and neutralize adding aq. NaOH to get desired amino compd.
The best technique for your reduction is to carry out the reaction in an aqueous-alcoholic medium. The solvent can dissolve the organic compound (Full or partially) which is sufficient for the reaction. You can use Zn or Sn dust in concentrated HCl under refluxing conditions for the reaction. After neutralization of the reaction mixture with NaOH, you will get the amine with metal oxide (as a colloidal mixture). Solvent extraction is required to get the organic compound in the organic medium. To get pure amine product, column chromatography with neutral alumina is required here.
Dear Pujan Sasmal many thanks for sharing this interesting chemical problem with the RG community. If you use tin and concentrated HCl the nitro compound will dissolve in the course of the reaction. For a typical protocol please see the attached pdf file:
https://chemistry.sites.clemson.edu/organic/Labs/2280Docs/ReductionNitroacetophenone.pdf
As suggested by Nayim Sepay it could be useful to add some ethanol to help solubilizing the nitro compound.
Also please have a look at the answers given to the following closely related technical question which has been asked earlier on RG:
What is the procedure of the reduction from NO2 to NH2 using Sn or SnCl2?
https://www.researchgate.net/post/What_is_the_procedure_of_the_reduction_from_NO2_to_NH2_using_Sn_or_SnCl2
In addition, please have a look atvthe following very instructive YouTube video:
Reaction of Nitroalkane With Sn Concentrated HCl - Compounds Containing Nitrogen
https://www.youtube.com/watch?v=XRAEB_Lj_Hg
Instead of tin you can also use iron powder and HCl for the reduction. There are numerous protocols for this method available on the internet.
Good luck with your work and best wishes, Frank Edelmann
For very insoluble nitro compounds, I had good results with acetic acid as solvent, and iron powder as the reducing agent. Even if the nitro compound doesn't dissolve initially, enough does go into solution to allow the reaction to proceed at room temperature, and eventually all of it will be dissolved and reduced.
The same solvent is also excellent for catalytic reduction (H2/PtO2).
I would agree with Dr. Demers that this reduction might proceed more cleanly with Fe powder in AcOH, however, for reduction with powdered Sn in HCl (normality?) addition of EtOH as suggested by Dr. Sepay should facilitate the reaction. Either way the complete reaction scheme should be looked at (i.e. what are all of the reaction products) which should dictate how to do the work up. There are metal salts to deal with in either case. It could be that in HCl of high enough normality 3-amino-5-methylbenzoic acid might precipitate as the HCl salt which would make work up more straightforward as long as the metal salts are soluble. A practical hint, on addition of powdered Sn to the reaction mixture considerable foaming can occur so using an oversized reaction flask is recommended.
Dear Pujan,
I hope Fe/NH4Cl in ethanol at 60 oC may helps you.
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