Question

Which of the following is NOT dihydric alcohol?

• A. Catechol
• B. Hydroquinone
• C. Phloroglucinol
• D. Resorcinol

Hint:

Memorize the isomer names for polyhydric phenols: Catechol, Resorcinol, and Hydroquinone are the ortho-, meta-, and para- isomers of dihydroxybenzene, respectively. Phloroglucinol stands out uniquely as a symmetric trihydroxybenzene.

Answer 1

The Correct Option is C

Step 1: Define dihydric.
A dihydric alcohol (or phenol) carries exactly two -OH groups. We must spot the one that does not.
Step 2: Recall catechol.
Catechol is benzene-1,2-diol: two -OH groups. Dihydric.
Step 3: Recall hydroquinone.
Hydroquinone is benzene-1,4-diol: two -OH groups. Dihydric.
Step 4: Recall resorcinol.
Resorcinol is benzene-1,3-diol: two -OH groups. Dihydric.
Step 5: Recall phloroglucinol.
Phloroglucinol is benzene-1,3,5-triol: three -OH groups. That makes it trihydric, not dihydric.
Step 6: Pick the odd one out.
Only phloroglucinol breaks the pattern, so it is the answer - option (3).
\[ \boxed{\text{Phloroglucinol is trihydric, not dihydric}} \]