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  1. I converted benzene into toluene by Friedel-Crafts alkylation reaction.
  2. Then by nitration I got two compounds o-nitrotoluene and p-nitrotoluene.

Is it possible to get only p-nitrotoluene?

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    $\begingroup$ I don't think there is a more effective (read: selective) way to do this conversion. Maybe check pubchem for another route, they have quite some references there. $\endgroup$ – Martin - マーチン Jan 6 '15 at 11:50
  • $\begingroup$ Solubility differences or other things $\endgroup$ – Arvin Kushwaha May 26 '16 at 12:54
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I'd doubt that exclusive nitration of toluene in para position is possible in homogenous solution.

But imagine to stuff a toluene molecule into a very narrow "tube". This tube will block any attack at C-2 (and C-3), while a nitrating agent may approach C-4.

Exactly this has been done in the vapour phase nitration of toluene with nitric acid over a zeolite (ZSM-5). See: Kalbasi, R.; Ghiaci, M.; Massah, A. Highly selective vapor phase nitration of toluene to 4-nitro toluene using modified and unmodified H3PO4/ZSM-5. Applied Catalysis A: General 2009, 353 (1), 1–8. DOI: 10.1016/j.apcata.2008.10.013.

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I think It can be done. But it's a rather long process.First prepare nitrobenzene from benzene by nitration.Then, convert it to aniline by adding a reducing agent(preferably Sn/Hcl).Then, Convert the NH2 group to NHCOCH3 by adding ethanoic anhydride in acetic acid(Which is a weaker activating group than NH2 but a stronger one as compared to CH3).Then, Add the methyl group by friedel-crafts alkylation. Then, convert NHCOCH3 back to NH2 by hydrolysis.Then, convert aniline to diazonium chloride by adding NaNo2 in Hcl. Finally convert diazonium chloride to Nitro group by Adding NaNo2/Cu. U get p-Nitrotoluene. But, I am not too sure this is acceptable.

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    $\begingroup$ This suffers from the same problems of selectivity (in the friedel-crafts step) as the OP's synthesis but it is far longer so will be much less efficient. $\endgroup$ – bon May 26 '16 at 12:43
  • $\begingroup$ I don't like the first process because practically we always have more than 1 molecule in a sample. Thus, After friedel crafts alkylation of benzene, After some time as the concentration of reactant decreases and that of product increases, Methyl Chloride may react with toluene(Since it is more activated than benzene)to give p-methyl toluene. Thus, p-nitrotoluene is not formed. $\endgroup$ – Sid May 26 '16 at 12:49
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    $\begingroup$ Your proposed Friedel-Crafts alkylation of aniline suffers from exactly the same problem... $\endgroup$ – orthocresol May 26 '16 at 13:22
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    $\begingroup$ F-C alkylation of aniline wouldn't work at all, as amino group would react with catalyst. $\endgroup$ – Mithoron May 26 '16 at 16:23
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    $\begingroup$ The product of your alkylation also has the amino group, do you think it just magically disappeared? $\endgroup$ – orthocresol May 26 '16 at 17:52

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