Question

What is the number of hydroxyl groups present in lactic acid?

• A. Zero
• B. Three
• C. Two
• D. One

Hint:

Only alcoholic \(-\mathrm{OH}\) groups are counted as hydroxyl groups, not those in \(-\mathrm{COOH}\).

Answer 1

The Correct Option is D

Step 1: Writing the structure of lactic acid.
Lactic acid has the structure \( \mathrm{CH_3-CH(OH)-COOH} \).

Step 2: Identifying hydroxyl groups.
There is one alcoholic hydroxyl group (\(-\mathrm{OH}\)) attached to the middle carbon atom.

Step 3: Clarifying the carboxyl group.
The \(-\mathrm{OH}\) present in the carboxylic acid group is not counted as a hydroxyl group separately.

Step 4: Conclusion.
Therefore, lactic acid contains one hydroxyl group.