Question

What is IUPAC name of catechol?

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

Hint:

Use an alphabetical memory trick for the dihydroxybenzene isomers moving from ortho to meta to para: Catechol (1,2) $\rightarrow$ Resorcinol (1,3) $\rightarrow$ Hydroquinone (1,4). CRH flows outward across the ring!

Answer 1

The Correct Option is B

Step 1: Identify the family.
Catechol is a dihydroxybenzene, meaning a benzene ring carrying two -OH groups. Its IUPAC name will end in -diol.
Step 2: Recall catechol's structure.
In catechol the two -OH groups sit on neighbouring carbons of the ring, i.e. the ortho positions.
Step 3: Number the ring for catechol.
Giving the lowest locants to adjacent -OH groups puts them at carbons 1 and 2, so catechol is benzene-1,2-diol.
Step 4: Contrast with resorcinol.
Resorcinol has its two -OH groups in the meta (1,3) arrangement, naming it benzene-1,3-diol, which is a different compound.
Step 5: Contrast with hydroquinone.
Hydroquinone has its -OH groups para (1,4), naming it benzene-1,4-diol, again different. The triol option is three -OH groups, also wrong.
Step 6: Select the answer.
The ortho 1,2 arrangement is catechol, so the name is benzene-1,2-diol, option (2).
\[ \boxed{\text{Catechol = Benzene-1,2-diol (option 2)}} \]