HCl + nitrate

[metal dragon]

Hello all,
Concentrated HCl has a p. H of 1 meaning it is extremely strong acid. When could HCl acid and a nitrate be used as nitrating mix? Say for nitrocellulose or mono-nitro-naphthalene? HCl I will be using is 30% but in quantity is not a problem. HCl should be the origin of H+ ions. In Alen, Mega and Mr cool all have a synthesis in which HCl is used with a nitrate (of memory I think it is hexamine-di-nitrate) Any comments are all welcome.
Thanks all!

[knowledgehungry]

IIRC the reaction HCl+nitrate <=> HNO3+chloride favors the left side so most nitrations arent succesful.

[frogfot]

Formation of nitro esters (for example NC) also needs this to happen:
HNO3 + H+ ==> NO2+ + H2O
HCl is probably too weak for this. I once tested to make NC by HCl/KNO3 without any success, however maby this method can be improved somehow??
Oh, and hexamine dinitrate is a nitrate salt, so thats another thing.

[kingspaz]

metal dragon, you will not recieve instant banning for the crime of posting a new topic with a low number of posts as i feel this topic is worth discussing and i have things to add :)
just be aware of the rules of the forum and the unofficial rules found in the water cooler as a sticky thread.

i don't believe this method will be of any use for any real nitrations. only for formation of nitrate salts. as other have stated.

the way i thought it worked is that HCl (being quite a strong acid) would donate H+ to any NO3- ions in the solution since NO3- is a stronger base than Cl- (well, thats what i remember). Thus you get a solution of HNO3 when you react a nitrate salt with a solution of HCl.

to form nitrate salts you just need a base. so if you throw hexamine into the now HNO3 solution you get HDN.

[knowledgehungry]

I thought Cl was stronger(not right word) than NO3. I thought the H+ were drawn to the Cl- cuz its more electronegative, but im not sure.

[vulture]

No, Cl will draw electrons to itself, making the formation and dissociation of H+ favourable.

[Al Koholic]

Think of it in terms of affinity. Cl- has a higher affinity (this can be determined by the acids dissociation constant) for H+ than does NO3- hence the lack of formation of HNO3. Sulfuric acid on the other hand has a much lower affinity for H+ than even NO3- and hence vacuum distillation of weaker HNO3 is possible from H2SO4 and XNO3.

The differences in affinity are caused by differing stability of the anions in question. Cl- happens to have a noble electron configuration, happens to be fairly electronegative, and happens to have a fairly large atomic radius leading to a good amount of stability in its charged form. Nitrate and sulfate are heteroatomic, double bond containing anions and hence can form resonance structures leading to a higher stability in a charged state and therefore less need for a proton to increase stability.

[metal dragon]

Thanks everybody, SWIM is going to test NC via HCl + KNO3. SWIM will be using 30% HCl, pure KNO3 and pure cotton. Does anybody know the correct formula and ratios for these chemicals? As soon as that is figured out I should be ready to begin. Maybe the reaction should be heated in order for the H+ ions to react. Any help would be appreciated? Thanks

[IPN]

I would use 3mols HNO3 to one mol of cellulose, although there is nothing to remove the water formed...

But anyways I would use the following amounts of chemicals:

109,374 ml HCL (100%, you will have to calculate the correct amount for 30%)
303,33 g KNO3
~10 g Cellulose (It's a small amount but considering the concentration of the HNO3 in the nitrating mix...)

[kingspaz]

IPN, exactly. esterification reactions are equilbirium reactions. thus if you can't remove the water you aren't going to form and ester (NC).
so in short metal dragon, its not going to work period.

[knowledgehungry]

Maybe if you bubbled 100% HCl through the reaction as it was occurring that might help in some way, it would shift the equilibrium.

[Al Koholic]

I still don't think you are even going to have a high enough concentration of HNO3...

You really need an acid with a larger Ka than HNO3 has in order to make a favourable equillibrium and HCl just won't cut it.

Think about it, the dissociated acid leads to an H+ and a conjugate base. When mixing KNO3 and HCl you are going to be left with an equilibrium that departs little from the initial conditions, IE: HCl, and KNO3.

Not to mention that there will be excess water all over the place. If you are going to attempt this I would agree with the above post in that you need dry HCl gas.

[kingspaz]

knowledgehungry,

cellulose + HNO3 <=> H2O + NC

equilibrium shift to counteract the change you put on them. thus, if you remove all the cellulose then any NC will turn back into HNO3 and cellulose to try and replace the ceullulose taken away.

so, to shift it the way we want (to make lots of NC) we must remove either the NC or the water. the NC is impossible to remove as it will be infinately mixed with ordinary cellulose fibres and in most cases attached to un nitrated fibres. thus, for a complete nitration all the water must be removed to convert ALL cellulose into nitro cellulose.

this is true of most exterification reaction, such as those of NG and MHN....

[Arthis]

Kingspaz you're right about the equilibrium phenomenom, but as cellulose is in a solid phase, its quantity in the mix will not affect the equilibrium point as long as there's at least a single cristal (fiber in this case :)).

Here, as water cannot be removed either due to the azeotrope formed with the remaining water, an excess of HNO3 is required to complete the reaction.

[knowledgehungry]

Adding more HCl would affect the equilibrium, but you would have to add more KNO3 also to make it shift to more NC, i forgot about that, but I meant that if you had excess HNO3 it would push the reaction right, very inefficient however.

[kingspaz]

Arthis, you're dam right. i forgot about that! :cool:

[Milamber]

Three suggestions... What if you make the nitric acid in some solvent that KNO3 is soluble in but KCl is not? The KCl would then precipitate and push the equilibrium to the nitric acid side. Only problem is finding a solvent - glycerol came to mind, but it might be nitrated in the reaction, which would probably not be a desired outcome under most circumstances...
Second, if I remember, isn't the pKa of HCl about -7, that of H2SO4 about -3 and HNO3 -1-ish? If this is right, HCl should be excellent for producing nitric acid... besides, even if the equilibrium made it inefficient, you could always just add extra nitrate to make it more favourable and then recover it later - a little more tedious, but might be useful for someone who has trouble getting sulfuric acid.
Finally, if you wanted to remove the water from a nirtation of cellulose, couldn't you use a dehydrating agent in the mix? The most obvious choice would be MgSO4, since not only is it common, but the worst thing that could happen if it reacted would be that you get H2SO4 and MgCl2 produced and that makes more nitric acid (by both moving the HCl equilibrium to the right and also due to the action of the sulfuric).

[frogfot]

Is it -7 in concentrated liquid form, or diluted?
Btw, there are another crap, the chloride would be oxidised by nitric acid producing free chlorine and NOx. This reaction is seen with diluted HCl/nitrate salt, and it will be faster with more concentrated HCl. So we loose lots of produced nitric acid.
(Oh, forgot to mention that CaCl2 as dehydrating agent doesnt seem to work here..)

[kingspaz]

anhydrous calcium nitrate can be used to dehydrate a mixture of HNO3 and glycerine to form NG.

[Arthis]

Making the reaction in a solvent where KCl is non soluble is a way to over-complicate things. Anyway, you need dry HCl gas, or your solvent needs to be non miscible with water.

Correct me if I'm wrong or if I missed something, but wouldn't this just be a complication and a all-in-one process for the good NA from DCM extractions process ?

[John Ashcroft]

In order for nitration to occur, the HNO3 must be protonated to yield a significant concentration of nitronium ions [NO2+]. They are the attacking species in a nitration. Aqueous HCl will not protonate HNO3 to a significant enough degree. In fact, you'll get more oxidation of HCl than nitronium ions (say hello to aqua regia whether you're mixing ionic nitrate with excess of HCl or nitric acid with excess of HCl).