I want to reduce the nitro to the amine group. But with Fe powder, requires column separation. I am interested in direct reductive products without the use of columns. Can this be achieved by sodium dithionite?
Dear Aashna Perwin sorry to see that your very interesting technical question has not yet received any expert answers from RG members. Personally I never tried a reduction of nitroaromatic compounds with sodium dithionite. However, sodium dithionite (Na2S2O4) is known to be a potent reducing agent. The reason lies in its sawhorse-like structure with a very long S–S bond. The S2O42– anion easily dissociates into SO2-. radical anions which are highly reducing. There are various hints in the chemical literature indicating that aromatic nitro compounds can be reduced to the corresponding anilines using sodium dithionite. For example, please have a look at the following potentially useful links:
Stoichiometric reduction with low valent sulfur (sulfide/dithionite)
https://reagents.acsgcipr.org/reagent-guides/nitro-reduction/list-of-reagents/stoichiometric-reduction-with-low-valent-sulfur-sulfide-dithionite
and
Sodium Hydrosulfite, Sodium Dithionite
https://www.organic-chemistry.org/chemicals/reductions/sodiumhydrosulfite-sodiumdithionite.shtm
Is this method better than reduction with Fe powder / HCl? I cannot say. In the end, the question if you need to use column chromatography for the purification of your products depends more on the nature of the products than on the synthetic method. Liquid products can also be purified by distillation, while solid products can be recrystallized from appropriate solvents.
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
Sometimes dithionite reduction procedure gives gum tar residues that might not be easy to remove without column separation. One thing to keep an eye on is purity of dithionite to be used in reaction.
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