Question

Which of the following compounds contains two primary alcoholic and one secondary alcoholic groups? ________.

• A. Ethylene glycol
• B. Isopropyl alcohol
• C. 3$^{\circ}$ Butyl alcohol
• D. Glycerol
• E. 2$^{\circ}$ Butyl alcohol

Hint:

Primary carbon: Attached to 1 other carbon. Secondary carbon: Attached to 2 others.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
This question requires the classification of alcohol functional groups (-OH) as primary (1\(^\circ\)), secondary (2\(^\circ\)), or tertiary (3\(^\circ\)). The classification depends on the number of other carbon atoms attached to the carbon atom that bears the -OH group.
- Primary (1\(^\circ\)): The -OH is on a carbon bonded to one other carbon. (e.g., in a -CH\(_2\)OH group) - Secondary (2\(^\circ\)): The -OH is on a carbon bonded to two other carbons. (e.g., in a >CHOH group) - Tertiary (3\(^\circ\)): The -OH is on a carbon bonded to three other carbons. (e.g., in a \(\equiv\)COH group)
Step 2: Detailed Explanation
Let's analyze the structure of each compound.
(A) Ethylene glycol (ethane-1,2-diol): HO-CH\(_2\)-CH\(_2\)-OH - Both -OH groups are on -CH\(_2\) carbons. Both are primary (1\(^\circ\)). - Contains: Two primary groups.
(B) Isopropyl alcohol (propan-2-ol): CH\(_3\)-CH(OH)-CH\(_3\) - The -OH group is on the central carbon, which is bonded to two other carbons. It is secondary (2\(^\circ\)). - Contains: One secondary group.
(C) 3\(^\circ\) Butyl alcohol (tert-butyl alcohol or 2-methylpropan-2-ol): (CH\(_3\))\(_3\)C-OH - The -OH group is on the central carbon, which is bonded to three other carbons. It is tertiary (3\(^\circ\)). - Contains: One tertiary group.
(D) Glycerol (propane-1,2,3-triol): HO-CH\(_2\)-CH(OH)-CH\(_2\)-OH - The -OH group on carbon-1 (an end carbon) is on a -CH\(_2\) group. It is primary (1\(^\circ\)). - The -OH group on carbon-2 (the middle carbon) is on a >CH group. It is secondary (2\(^\circ\)). - The -OH group on carbon-3 (the other end carbon) is on a -CH\(_2\) group. It is primary (1\(^\circ\)). - Contains: Two primary groups and one secondary group. This matches the question's criteria.
(E) 2\(^\circ\) Butyl alcohol (sec-butyl alcohol or butan-2-ol): CH\(_3\)-CH(OH)-CH\(_2\)-CH\(_3\) - The -OH group is on a carbon bonded to two other carbons. It is secondary (2\(^\circ\)). - Contains: One secondary group.
Step 4: Final Answer
Glycerol is the compound that contains two primary alcoholic groups and one secondary alcoholic group.