-1
$\begingroup$

Which EAS (electrophilic aromatic substitution) reactions does nitrobenzene show?

We know that nitrobenzene is particularly deactivated towards most such reactions, as the nitro group is strongly electron withdrawing via resonance and inductive effects. However, I wish to know exactly where to draw the line - which reactions nitrobenzene undergoes, and which ones it doesn't.

Of course, there's no clear boundary as to whether or not a compound undergoes a particular EAS, but can't we at least comment on the yield obtained in such reactions?

I haven't been able to find much about EAS reactions of nitrobenzene online, hence I come to Chem SE, seeking data and sources.

The reactions of interest are:

1.Friedel Crafts Alkylation, Acylation

2.Nitration (concentrated sulphuric and nitric acid)

3.Sulphonation (fuming sulphuric acid)

4.Halogenation in presence of Lewis acids etc.

Please help! Thanks a lot!

$\endgroup$
3
$\begingroup$

Of course, there must be some boundary as to whether or not nitrobenzene undergoes a particular electrophilic aromatic substitution (EAS) since nitro-group is very deactivating. I leave it to you to decide that fact on the yield obtained in following reactions, because there are some data you may fail to find but, nonetheless, exist in literature.

Chlorination of nitrobenzene at $\pu{35\!-\! 45 ^{\circ}C}$ in the presence of iron (III) chloride ($\ce{FeCl3}$) gives an isomer mixture, which contains 86% 3-chloronitrobenzene, 10% 2-chloronitrobenzene and 4% 4-chloronitrobenzene (Ref.1). Even if nitro group is $m$-directing, this reaction has given significant amount of $o$-prodouct. You may compare this reaction with nitration reaction of chlorobenzene at $\pu{40\!-\! 70 ^{\circ}C}$ with mixed acids (30% $\ce{HNO3}$ : 56% $\ce{H2SO4}$ : 14% $\ce{H2O}$), which typically gives a 98% yield of an isomer mixture consisting of 34-36% 2-chloronitrobenzene, 63-65% 4-chloronitrobenzene, and about 1% 3-chloronitrobenzene (Ref.1).

A simple and efficient method for the sulfonation of nitrobenzene using liquid $\ce{SO3}$ as the sulfonating agent in a microreactor at $\pu{40\!-\! 110 ^{\circ}C}$ was developed and conducted recently, and 88% yield of 3-nitrobenzenesulfonic acid (m-NBSA) has been obtained (Ref.2). The main by-product is bis(3-nitrophenyl)sulfone (BNPS) and proposed mechanism was depicted in the following Figure:

Mechanism for synthesis of m-nitrosulfonic acid

On the other hand, the sulfonation of toluene has given $o:m:p$ ratio of 21.2% : 2.1% : 76.7% in 77.8% $\ce{H2SO4}$ (Ref.3). The $o:m:p$ ratio has become 38.8% : 2.6% : 58.6% when solvent has changed to 84.3% $\ce{H2SO4}$ (significant decrease of $p$-product in increasing acidity; Ref.3). Also, note that the sulfonation by sulfuric acid of nitrobenzene itself and of various aromatic compounds in nitrobenzene solution has been studied at a series of temperatures (Ref.4). Yet, no concomitant sulfonation of nitrobenzene in the presence of other activated substrates such as toluene and xylene has been reported.

Using $\ce{NO2+PF6-}$ as the nitrating reagent, Olah had studied nitration of nitrobenzene in two different solvents: He achieved $o:m:p$ ratio of 7.1% : 91.5% : 7.4% in 96% $\ce{H2SO4}$ and that of 10% : 88.5% : 1.5% in $\ce{CH3NO2}$ (Ref.3).

For comparison, same nitrating agent ($\ce{NO2+PF6-}$) has given $o:m:p$ ratio of 68.2% : 2% : 29.8% in $\ce{CH3NO2}$ when subjected to nitrate toluene (Ref.3).

To my knowledge, Friedel-Crafts reaction of nitrobenzene (alkylation or acylation) is yet to be known. I'd love to hear if somebody say otherwise.


References:

  1. International Agency for Research on Cancer (World Health Organization), lARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol. 65, 1996, “2-Chloronitrobenzene, 3-chloronitrobenzene and 4-chloronitrobenzene,” pp. 263-296.
  2. Y. Chen, Y. Su, F. Jiao, G. Chen, “A simple and efficient synthesis protocol for sulfonation of nitrobenzene under solvent-free conditions via a microreactor,” RSC Adv. 2012, 2, 5637–5644 (DOI: 10.1039/C2RA20406A).
  3. George A. Olah, “Aromatic substitution. XXVIII. Mechanism of electrophilic aromatic substitutions,” Acc. Chem. Res. 1971, 4(7), 240–248 (DOI: 10.1021/ar50043a002).
  4. F. J. Stubbs, C. D. Williams, C. N. Hinshelwood, “The Kinetics of Aromatic Sulphonation Reactions. Sulphonation by Sulphuric Acid in Nitrobenzene Solution,” J. Chem. Soc. 1948, 1065–1078 (DOI: 10.1039/JR9480001065).
$\endgroup$
  • $\begingroup$ What about nitration of nitrobenzene using HNO3 + H2SO4? $\endgroup$ – arya_stark May 4 at 3:32
  • $\begingroup$ Reference 3 has that values as well. $\endgroup$ – Mathew Mahindaratne May 4 at 4:17
  • $\begingroup$ Thanks, that clears it! $\endgroup$ – arya_stark May 4 at 9:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.