Question

Select the correct IUPAC name of pyrogallol.

• A. Benzene-1,3-diol
• B. Benzene-1,4-diol
• C. Benzene-1,3,5-triol
• D. Benzene-1,2,3-triol

Hint:

Pyrogallol = 1,2,3-trihydroxybenzene (adjacent OH groups).

Answer 1

The Correct Option is D

Concept:
Pyrogallol is a derivative of benzene containing three hydroxyl (\(-\text{OH}\)) groups. It is a type of trihydroxy benzene, and its IUPAC name depends on the positions of these \(-\text{OH}\) groups on the benzene ring. Step 1: Understand the structure of pyrogallol. Pyrogallol has three hydroxyl groups attached to adjacent carbon atoms of the benzene ring.
Step 2: Assign numbering to the ring. Numbering is done such that substituents get the lowest possible numbers: \[ \text{OH groups at positions } 1, 2, 3 \]
Step 3: Write the IUPAC name.

• Benzene ring → parent chain
• Three OH groups → triol
• Positions → 1,2,3

\[ \text{Name} = \text{Benzene-1,2,3-triol} \]
Step 4: Eliminate incorrect options.

• (A) and (B): only two OH groups (diols) $\times$
• (C): positions 1,3,5 (not adjacent) $\times$
• (D): correct adjacent positions \checkmark

Step 5: Conclusion. \[ \text{Correct IUPAC name = Benzene-1,2,3-triol} \]