Guys, as far as my question regarding HNO3, it WASN'T regarding organic nitration. But a means to prepare copper nitrate, without a contaminating sodium or potassium cation, as the copper is intended for a catalytic purpose. Had been doing it with mixed nitrate salt (NaNO3) and sulfuric, to generate HNO3 in-situ.
But of course, the cleaner, the better, and less farting about with extraneous stuff having to be cleaned after roasting the nitrate to produce copper oxide to convert to CuCl2, recycling the NOx to reclaim my nitrate salt or reclaim it as HNO3, depending on whether or not a solution of sodium bicarbonate is used in the Dreschel bottles (one empty, interposed, to prevent suckback) or H2O alone. That being a secondary consideration based on atom economy and my tendencies to recycle and find new uses for old side products wherever feasible without loss of quality control.
I'm not entirely sure, as to the structure of the catalyst in question, generated by in-situ reduction of CuCl2 in aqueous solution added to isopropanolic sodium borohydride, there is no doubt the system is being utilized, by others, to reduce C3 nitroalkanes to aminoalkanes after borohydride reduction of nitroalkenes to the nitroalkane, with excess NaBH4 to prevent that parasitic (and rather incestuous) Michael addition between substrate nitroaliphatic and it's parent nitroalkene.
The second step has been said to be copper nanoparticles, but to me, it seems an awful lot like the technique used in preparation of binary metal borides, such as Ni2B, in a sort of hybrid version between P1 and P2 type dinickel boride (P1 is more active, prepared in alcoholic media, P2 is less active, using aqueous solution, both via borohydride reduction of a nickel salt, NiCl2 is used by some, but a preferable alternative is to use the acetate in the case of nickel boride. Same processes used to make cobalt boride, so, I can't help but question, whether this is producing copper NPs, as has been said, or if the product is something with a likely stoichiometry of Cu2B.
Either way it is being used by folk for the reduction in question and they are getting their results, proof of the pudding is in the eating, as they say.
But, what is driving me up the wall, is not knowing for sure if it's a binary boride, or if it's CuNPs as claimed. Visually, there isn't much to say, save for the reaction, before use for a reduction process, affords a finely divided black product, that forms a slurry if stripped of much solvent, both in the case of nickel boride (I've only ever made P2 nickel boride though, using the acetate salt, and it, too, is a fine black suspension of insoluble particles.
Anybody know if acidification of these binary borides with a non-oxidizing strong acid would, in the case of, after thorough washing to remove remains of borohydride and residues of it's decomposition containing boron, repeated until eventual evaporation of solvent. after decanting most of it off, with no organics to be reduced, afford diborane upon acidification, with transition metal borides, in particular, copper borides? because I've been scratching my head what with sadly, not having a basement with an ICP-MS setup and an electron microscope to take a peek at what is going on in there.
So testing for boron via liberation of diborane seems like a way to go, possibly? (yes, I am aware of it's high toxicity, pyrophoricity, gaseous nature, and if pentaborane has anything to go by, an atrocious stench in even trace quantities, not something I'd undertake without the appropriate great care, on small scales for analysis of boron content in the product, and subsequent deliberate pyrolysis of all exit gases, again, to examine for chemical behaviour as well as neutralizing the threat of diborane itself.
