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I've learnt that the $\ce{OH}$ group is 2- and 4-directing, but this has caused some confusion. If $\ce{HNO3}$ reacts with phenol, would there be any 2,6-dinitrophenol produced?

I know that the first nitro group will add to position 4 or 2, but if one is added to 2, can a second add to 6? Or must position 4 be added prior to 6?

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    $\begingroup$ Yes, there would be. $\endgroup$
    – Mithoron
    May 15, 2023 at 15:13
  • $\begingroup$ In my textbook it only shows 2- and 4- nitrophenol, along with 2,4,6-trinitrophenol, is that because it's hard to isolate 2,6-nitrophenol, and it's much more likely that all the possible hydrogens have been substituted? $\endgroup$
    – nav op
    May 15, 2023 at 15:15
  • $\begingroup$ It's too minor of a product. $\endgroup$
    – Mithoron
    May 15, 2023 at 15:16
  • $\begingroup$ The products of nitration of phenol depend on various factors. For example, different nitrating reagents gave different ratio of products. $\endgroup$ May 15, 2023 at 16:08
  • $\begingroup$ See here for example. $\endgroup$ May 15, 2023 at 17:54

2 Answers 2

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As mentioned in the comments, the products depends on various factors like nitrating agent, concentration etc. If you use dilute nitric acid, you will get a mixture of mononitrophenol but when you use concentrated nitric acid, you will get picric acid. Note that although picric acid is the targeted product, you will get all sorts of dinitro- and mononitro- isomers as well. To get pure picric acid, steps are taken to distill of the DNPs and MNPs or make the reaction more selective. So, 2,6-dinitrophenol is also a product of the reaction. It's just that it's too minor of a product to mention.

Side information:

Pure 2,6-DNP can be prepared by separate sulfonation and nitration of o-nitrophenol. It is also a byproduct in the synthesis of 2,4-DNP (2,4-Dinitrochlorophenol is heated with 6% aq. $\ce{NaOH}$ at 95-100 °C for 4 hours which hydrolyzes it. 2,4-DNP is the product and is precipitated by adding acid and is filter off. The solution contains the more soluble 2,6-DNP which is separated by adding excess of acid).

Source: Toxicological Profile for Dinitrophenols, U.S. Department of Health and Human Services, 1993

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Yes, nitration of phenol with nitric acid can yield 2,6-dinitrophenol.

Here is a diagram showing the possible products of the nitration of phenol with nitric acid:

        OH
        |
       C6H5

Nitration at position 2:

        NO2
        |
       C6H4OH

Nitration at position 4:

        NO2
        |
       C6H5OH

Nitration at position 6:

        NO2
        |
       C6H4NO2OH

2,6-dinitrophenol:

        NO2
        |
       C6H3(NO2)2OH
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    $\begingroup$ The site allows to upload illustrations in e.g. the .png file format. For clarity of your answer, structural formulae would be of advantage in comparison to your diagrams. Get familiar with a couple of them (a list, and a review). In absence of a (personal/group/uni campus) license, visit their demo pages (for example ChemDraw, Marvin, ChemDoodle). $\endgroup$
    – Buttonwood
    Oct 13, 2023 at 8:10

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