# Making o-bromoaniline from aniline

How can I make o-bromoaniline from aniline (as a major product)?

I know how to make p-bromoaniline from aniline, by acetylation followed by treatment with $\ce{Br2}$/$\ce{CH3COOH}$ and hydrolysis. But in this process the ortho isomer (if formed) will be the minor product.

• Did you consider different sequences? Remember that aromatic nitro compounds can be reduced to the corresponding amines ;-) Mar 8 '16 at 8:08
• @Klaus Warzecha But even if I consider nitro benzene, the ortho isomer will be the minor product. Would the yield be satisfactory ? Mar 8 '16 at 8:18
• Remember how the nitro group directs. If you start with nitrobenzene, chances are good that the bromination will almost exclusively yield the meta-substituted product. But what if you try to nitrate bromobenzene? Mar 8 '16 at 8:29

Didn't you consider the way through sulfanilic acid, the para-position will be protected. In this case both substituents will direct the electrophilic substitution in ortho- position with respect to amino group. Then remove sulfonic acid group by desulfonation and you will obtain your ortho-bromoaniline.

• Wont it exist in zwitter ion form and loose its directing influence? Feb 17 '20 at 8:46

As outlined in a comment direct bromination of nitrobenzene with $\ce{Br2}$ and $\ce{FeBr3}$ is likely to give the meta-substituted product.

If you want to avoid time-consuming and expensive procedures, your options are:

• Change the order of events. Nitrate bromobenzene under mild(er) conditions, or
• Find conditions, under which bromination of nitrobenzene furnishes the ortho-product

For the latter, have a look at Chem. Commun., 1996, 2679-2680 (DOI). The authors state:

We have observed that monosubstituted benzene derivatives react with a mixture of dimethyl sulfoxide and aqueous hydrobromic acid […] to yield regiospecifically only the monobromo derivatives. It is interesting to note that electron- withdrawing groups such as $\ce{NO2}$, $\ce{CHO}$ yield ortho-bromo derivatives, while electron-donating groups such as $\ce{NH2}$, $\ce{OH}$ or $\ce{Me}$ give only para-bromo derivatives.

I think that you probably cannot avoid separating ortho from para isomers (and possibly disubstitution products) after using a method like the one you suggest or a method of blocking the para- position.

Another method that is probably not taught to undergraduates (?) is the Directed ortho metallation (DoM) or Snieckus chemistry. The image below has been copied from that link.

• My pleasure :). Mar 8 '16 at 19:34