[organoman]

hi all,
I am working on preparation of 4-nitroxylene.However general nitration of xylene with fuming nitric acid leads to the mixture of 3-nitroxylene and 4-nitroxylene almost in 50-50 ratio.
Can somebody suggest me a better route which is easy to carry out in laboratory and not so costly also.

[kiwi]

In theory i guess you could nitrate a strongly directed substrate like o-cresol, then after conversion of the phenol to the triflate couple on the extra methyl group via some sort of Pd coupling. But thats a long way to go for a simple compound, can you just column/crystallise out the desired isomer from your mixture? Buying a lot of xylene and nitric acid and throwing half your product away is probably still cheaper than buying more expensive reagents.

[sjb]

Which xylene are you working with? From your description of your observed products, I'd guess o-xylene (1,2-dimethylbenzene), but just wanted to be sure.

Do you really need to hit it as hard as fuming nitric? Given the methyl groups would activate the ring, perhaps nitronium tetrafluoroborate, or similar?

Have you seen Proc. Chem. Soc., 1961, 357 http://dx.doi.org/10.1039/PS9610000357 ?

From the googled cache it seems that the 4-isomer predominates here ~2:1 over the 3, but I don't have access to the full paper to be certain.

Or perhaps David A. Burgess and Ian D. Rae, Aust. J Chem., 1977, 30, 927-31 or Lennart Florvall and Maj-Liz Persson, Acta. Chemica. Scandinavica B, 36 (1982) 141-146 - both report use of 4-nitroxylene in further transformations (from http://www.patentstorm.us/patents/6132944-description.html)

What do you need it for, perhaps another way around the maze might help?

S

[gtaskiran1977]

May be you can try to heat just a little.

[organoman]

I would like to add to the information. Yes it is o-xylene to start with. I have tried the reaction at different temperature (0-50 deg C)and concentration of fuming nitric acid. The ratio of two isomers more or less remains same. However I have observed that at higher temperature diniration increases.
Perhaps this can give some more clue.
Anyway thanks for your inputs.

[hmx9123]

The book 'Nitration' by George Olah goes into great detail about aromatic nitration, and what nitration agents promote what isomer.  I would check that out.