Question

Glycerol has __________ reactive hydroxyl groups.

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

Hint:

Glycerol is a triol (trihydric alcohol), meaning it has 3 reactive hydroxyl groups capable of forming ester bonds with up to 3 fatty acid molecules.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Lipids are major macronutrients composed primarily of fatty acids esterified to a glycerol backbone.
Understanding the chemical structure of glycerol is essential for analyzing the synthesis of mono-, di-, and triacylglycerols.

Step 2: Detailed Explanation:
Glycerol (botanically and chemically classified as propane-1,2,3-triol) is a simple trihydric alcohol with the chemical formula:
\[ \text{C}_3\text{H}_8\text{O}_3 \] Its structural formula is represented as:
\[ \text{CH}_2(\text{OH})-\text{CH}(\text{OH})-\text{CH}_2(\text{OH}) \] From this structure, it is clear that each of the three carbon atoms in the glycerol molecule is bonded to a single hydroxyl (\(-\text{OH}\)) group.
Therefore, glycerol possesses exactly three reactive hydroxyl groups:
1. Two primary hydroxyl groups located on the terminal carbon atoms (C1 and C3).
2. One secondary hydroxyl group located on the central carbon atom (C2).
These three hydroxyl groups can undergo esterification reactions with the carboxyl groups of fatty acids to form monoacylglycerols (one fatty acid), diacylglycerols (two fatty acids), or triacylglycerols (three fatty acids, which represent standard fats and oils).

Step 3: Final Answer:
Therefore, Glycerol has Three reactive hydroxyl groups.