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The reaction of phenol with nitric acid is a mono-nitration reaction i.e. Only one hydrogen atom gets replaced per molecule of phenol. The products formed are o-nitrophenol and p-nitrophenol.

The reaction of phenol with concentrated nitric acid in the presence of sulphuric acid, however, is a tri-nitration reaction.the product is 2,4,6-trinitrophenol (commonly called picric acid ).

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