Sciencemadness Discussion Board

nitration of xylene using HNO3/DCM mixture

mackolol - 28-2-2018 at 08:35

Hi, I want to make 2,6 xylidine and i dont have better idea than to make it from mixed xylenes. However separation of isomers is huge pain in the ass. So im wondering if toluene nitrated by this mixture forms only ortho isomer then if it will work with xylene, what isomers will be created and if this will help in any point.

sykronizer - 6-3-2018 at 16:54

Look up Urbanski there is plenty of literature concerning different nitration mixtures and nitration of Xylene...typically around 80 percent sulfuric and 20 percent nitric is a mixture that will get you to trinitro xylene in one step...but you MUST read the literature regarding the temperature control because it can cook off and that's the last thing you want..


[Edited on 7-3-2018 by sykronizer]

Boffis - 8-3-2018 at 06:03

@mackolol, I have been reading up on this subject. From what I can find in papers by Strazzolini et al. (bull.chem.soc.japan Strazzolini et al 1995 p1155-1158 and JOrgChem Strazzolini et al 1998; v63; p952-958) the use of HNO3 in DCM in the nitration of toluene only enhance the yield of o isomer when the methyl group is substituted and that you get pretty much the same isomer ration as with mixed acid for toluene. My understanding is that you need an oxygen bearing group on the methyl group to coordinate with the nitric acid prior to nitration. So on this basis I would be surprises if you got any difference in isomer ratios between HNO3-DCM and mixed acids with m-xylene.

According to Kobe and Brennacke (Industrial and Engineering Chemistry, 1954, vol 45, p728-732) the nitration of m-xylene under mild conditions yields only about 15% 2-nitro-m-xylene and 85% nitro-m-xylene. It does not sound likely that the use of anhydrous nitric acid in DCM will significantly increase this.

I would check out Reaxys if you know someone with access or have access to the ref section of MS. There may be indirect routes say by low temperature sulphonation of m-xylene to m-xylene-4-sulphonic acid, low temperature nitration of this to 2-nitro-m-xylene-4-sulphonic acid followed by hydrolysis to the 2-nitro derivative. I don't know if this scheme would work but I'll bet that the old boys had worked out a route back in the hay-days of the dye industry.

Lidocaine may be a possible source since it occasionally pops up on eBay Europe; unless of course that's what you are trying to make.

mackolol - 10-3-2018 at 10:15

Yup i'm trying to make lidocaine and it would be great if it was pure enough to test it safely on myself. (I have access to lidocaine but want to make it on my own). And as You know Boffis i've tried separating xylene isomers by sulfonation but I didnt make it. It's so hard to say if it is meta isomer because all of them participate in this reaction.

Keras - 26-7-2019 at 09:07

I am sorta resurrecting this thread, because I find the idea (i.e. to synthesise lidocaine) interesting.

Did you have any success in nitrating your xylene mixture?

I would probably first try to isolate m-xylene from its other isomers. Apparently, m-xylene forms an azeotrope with water, and the other isomers don’t. I'm not sure about that, though.

Herr Haber - 29-7-2019 at 03:49

Urbanski tome I mentions a few methods of separation before or after nitration.
It also suggests the best source for xylene depending on what isomer you are looking for.

Always a great read :)

Keras - 7-11-2025 at 23:42

Wow this is old, but thinking back about it I wonder.

Nitration under mild conditions (~20 °C) of a mixture of xylene isomers should only produce nitro-m-xylene. Given the position of the methyl groups in o- and p-xylene, they cancel their slight activating action, whereas it is reinforced in m-xylene, so probably only m-xylene would get nitrated to a significant amount.

Now it remains to see:

1. How to separate the nitro products from unreacted xylene.
2. How to separate 2-nitro-m-xylene from 4-nitro-m-xylene.

If anyone has an idea…

bnull - 8-11-2025 at 11:33

You may first separate the isomers of xylene. m-xylene dissolves in 80% H2SO4 at room temperature but the other two do not.

I'm gonna check the rest of the stuff.

Fery - 8-11-2025 at 22:06

Quote: Originally posted by Keras  
How to separate the nitro products from unreacted xylene

https://www.sigmaaldrich.com/US/en/product/aldrich/n28353
1,3-Dimethyl-2-nitrobenzene bp 225 °C

https://www.sigmaaldrich.com/US/en/product/aldrich/171018
2,4-Dimethyl-1-nitrobenzene bp 244 °C

o-xylene bp 144 C
m-xylene bp 139 C
p-xylene bp 137 C
Quote: Originally posted by Keras  
How to separate 2-nitro-m-xylene from 4-nitro-m-xylene

chromatography

Fery - 8-11-2025 at 22:37

read this:
https://sci-hub.st/10.1021/ie50532a036

Attachment: kobe1954.pdf (577kB)
This file has been downloaded 121 times
Quote:
the entire reaction mass was washed into the steam-distillation flask and diluted to reduce the sulfuric acid concentration to less than 30%
The whole mixture was then steam distilled and the condensed vapors were passed through a trap. To make the trap effective, it was found necesary to extend the condenser outlet beneath the surface of the liquid in the trap. When the organic phase in the trap began to sink, it was collected and weighed as mononitro-m-xylene.



and this:
https://www.researchgate.net/publication/380627416_Chemo-and...

Attachment: Chemo-and_regioselective_aqueous_phase_co-acid_fre.pdf (1.3MB)
This file has been downloaded 59 times
Quote:
The starting concentration was 15.8 M (70% HNO3), as this nitric acid concentration is commercially widely available. The data are tabulated in Table 2. The most important observation during the above dilution experiments was that none of the concentrations yielded di-nitroproducts. This is an important step forward as the major goal is to achieve selective mono-nitration. It appears that the commercially available 15.8 M sample provided reasonable yield and 4-nitroregioselectivity. Further diluting this sample to 14 M resulted in a considerable drop in conversion, while the selectivity remained similar.

table 2:
15.8M HNO3 total conversion 66%, ratio of products 85% 2,4-Dimethyl-1-nitrobenzene : 15% 1,3-Dimethyl-2-nitrobenzene
14M HNO3 total conversion 23%, ratio of products 80% 2,4-Dimethyl-1-nitrobenzene : 20% 1,3-Dimethyl-2-nitrobenzene


[Edited on 9-11-2025 by Fery]