Sciencemadness Discussion Board

Reducing nitroguanidine with dithionite

Chisholm - 12-7-2017 at 07:21

Nitroguanidine is more interesting as a precursor to other substances than as an explosive in its own right.

Most prominently, it is a feedstock for aminoguanidine, which is a precursor for tetracene and tetrazole-based primaries.

I've tried the zinc-acetic acid method of reducing nitroguanidine and had no success whatsoever. The typical response would be to acquire better-quality zinc and activate it with 3% HCl before use, but after I saw ChemPlayer's video on reduction of aromatic nitro compounds with sodium dithionite, I wondered if alkaline sodium dithionite might work for reducing nitroguanidine.

The idealized equation would be:

3 Na2S2O4 + 1 CH4N4O2 + 6 NaOH = 1 CH6N4 + 6 Na2SO3 + 2 H2O

The initial procedure seems simple enough; dissolve the sodium hydroxide in water (warming it up and increasing solubility), then add the dithionite, then add the nitroguanidine and maintain heating and stirring until the yellow color has vanished. Then add sufficient hydrochloric acid to convert the bisulfite to sodium chloride and SO2 and neutralize the aminoguanidine freebase, heat until all SO2 and excess HCl have been driven off, then add a solution of sodium carbonate to precipitate the aminoguanidine as the bicarbonate salt. Filter, wash with water and ethanol, then dry.

Am I missing anything?

Boffis - 14-7-2017 at 00:06

Aminoguanidine is a strong base but rather susceptable to hydrolysis and I think you need the acidic conditions to minimizes this. Over reduction leads to ammonia and guanidine salts. Personally I think that under the strongly alkaline conditions you envisage you will not get aminoguanidine but ammonia, even guanidine hydrolyses under strongly basic condition if heated.