[herrhansen]

Hi everybody.

I recently nitrated my activated aromatic by using 68% nitric acid and it was just fine. Now I only Got stock of 62% nitric acid.

Does anyone know if it would do the job just as fine as the 68 %? Normally I have seen diluted nitric acid solution in nitrating Jobs, whenever there was a tendency of polymerization of the products. So my guess is the 62 % solution should work just fine?

If anybody knows, then please let mé
Know. Thanks in advance.

[Åke]

Hi!

Why not just try on a small scale and know for sure?

[nox]

Somehow I really, really doubt that 6% dilution would make a difference.

[OC pro]

Yeah makes no difference. You could also try Claycop. I got better yields in most cases.

[herrhansen]

Thanks for replies.

I would like to conduct it on a smale scale, but as I have to make a conversion before I can nitrate I would rather do it all at once if it is possible.

But I think too it is possible. I just had to be convinced :-)

The claycop seems effective, but I have obtained good yields by just dissolving my product in 68 % nitric acid. But maybe another time if I have to control the nitration. Thanks.

[opsomath]

I would bet that it works. I always did these in acetic acid with only one equivalent or a little more of nitric acid; you might try that if you run into problems.

[herrhansen]

Thanks for replies.

It worked just fine thanks.

[408]

I have never seen a difference for 60% vs 70% for activated aromatics.  If you are worried toss in some sulfuric or oleum.  If something is easily nitrated it makes no difference usually. 

[orgopete]

I would bet that it works. I always did these in acetic acid with only one equivalent or a little more of nitric acid; you might try that if you run into problems.

In general, one should be able to anticipate the effect of acid concentration by a simple stoichiometry calculation (or just thinking about it). In this example, and remember, water is the by-product, what is the nitric acid concentration for the last nitration?

I could be wrong on this because I don't recall having done one of these nitrations with reactive aromatic rings, but I think nitric acid is added to the aromatic ring. The reaction is controlled by stopping the addition. In this case, the nitric acid concentration falls as the reaction proceeds.

I always like to think in this way about reactions as they proceed. If they slow down, why might they slow down? What can I do to speed them up, etc.?

[opsomath]

I'm sorry, but I'm not sure exactly what you're saying here.

[orgopete]

I'm sorry, but I'm not sure exactly what you're saying here.

Okay, bear with me. Had the original poster given actual reaction conditions, I could get this right. Let us assume we need to nitrate 1 mole and we used a 50% excess of 68% nitric acid.

Start: 1.5 mol x 63 g = 94.5 g HNO3
139 g x 68% = 94.5 g HNO3
139 g - 94.5 g = 44.5 g H2O

End:
94.5 g HNO3 - 63 g HNO3 = 31.5 g HNO3
44.5 g H2O + 18 g H2O = 62.5 g H2O
31.5 g HNO3/(31.5 g + 62.5 g) = 0.33

Without having done anything, will 62% nitric acid work in this reaction? Well, the concentration range for my hypothetical reaction gives the product with the nitric acid concentration falling from 68% down to 33%. So, I would say yes, 62% should work as well. If we knew the actual stoichiometry of the proposed reaction, we could calculate that final concentration. 

If a smaller excess of nitric acid were used, then the concentration would fall to an even lower value. Since the reaction depletes the nitric acid, then a higher rate can be obtained by simply adding more nitric acid. Presumably, if one were forced to start with a lower concentration of nitric acid, one could increase the amount of nitric acid to obtain the same final concentration.