Which of the following statements about 2,4,6-trinitrophenol (picric acid) are correct?

AIts anion is stabilised mainly by the nitro group at C-4, the other two nitro groups having no effect on acidity.
BIts $p K_{a}$ (about 0.4) is lower than that of ethanoic acid (about 4.8).
CIt liberates $CO X_{2}$ from aqueous $NaHCO X_{3}$ .
DIt can be prepared from phenol by treatment with conc. $HNO X_{3}$ in the presence of conc. $H X_{2} SO X_{4}$ .

Answer: B, C, D

Three nitro groups (two ortho, one para) stabilise the anion by

- R

and

- I

effects, making picric acid a stronger acid than ethanoic acid and strong enough to decompose bicarbonate. It is made by exhaustive nitration of phenol with conc.

HNO X_{3}

/conc.

H X_{2} SO X_{4}

. All three nitro groups, not only one, contribute, so the last statement is false.

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Which of the following statements about 2,4,6-trinitrophenol (picric acid) are correct?

Answer: B, C, D

More questions on Phenols: acidity, Kolbe, Reimer-Tiemann, electrophilic substitution