Question

Glycerol is a trihydric alcohol. It contains _____
 

• A. One primary, one secondary and one tertiary alcoholic groups
• B. Two primary and one secondary alcoholic groups
• C. Two secondary and one primary alcoholic groups
• D. One primary and two tertiary alcoholic groups

Hint:

To classify alcohols, first identify the carbon atom bearing the -OH group. Then, count how many other carbon atoms are directly bonded to it. 1 C-bond = primary, 2 C-bonds = secondary, 3 C-bonds = tertiary.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:  
The question asks to identify the types of alcoholic groups present in glycerol, which is a trihydric alcohol. 
Step 2: Analyzing the Structure of Glycerol: 
Glycerol is also known by its IUPAC name, propane-1,2,3-triol. Its chemical structure is: 
\[ \begin{array}{c} \text{CH}_2\text{OH} \\ | \\ \text{CHOH} \\ | \\ \text{CH}_2\text{OH} \end{array} \] Or written linearly: HO-CH\(_2\)-CH(OH)-CH\(_2\)-OH. 
Step 3: Classifying the Alcoholic Groups: 
The classification of an alcoholic group (-OH) depends on the type of carbon atom it is attached to. 
- A primary (1\(^\circ\)) alcohol has the -OH group attached to a primary carbon (a carbon atom bonded to only one other carbon atom). 
- A secondary (2\(^\circ\)) alcohol has the -OH group attached to a secondary carbon (a carbon atom bonded to two other carbon atoms). 
- A tertiary (3\(^\circ\)) alcohol has the -OH group attached to a tertiary carbon (a carbon atom bonded to three other carbon atoms). 
In glycerol: 
- The two terminal carbons (C-1 and C-3) are each bonded to only one other carbon atom (C-2). Therefore, they are primary carbons. The -OH groups attached to them are primary alcoholic groups. There are two primary alcoholic groups. 
- The central carbon (C-2) is bonded to two other carbon atoms (C-1 and C-3). Therefore, it is a secondary carbon. The -OH group attached to it is a secondary alcoholic group. There is one secondary alcoholic group. 
- There are no tertiary carbon atoms in glycerol. 
Step 4: Final Answer: 
Glycerol contains two primary and one secondary alcoholic groups.