Question

Which of the following is primary allylic alcohol?

• A. \(\text{H}_2\text{C} = \text{CH} - \text{CH}(\text{CH}_3) - \text{OH}\)
• B. \(\text{H}_2\text{C} = \text{CH} - \text{CH}_2 - \text{OH}\)
• C. \(\text{H}_2\text{C} = \text{CH} - \text{C}(\text{CH}_3)_2 - \text{OH}\)
• D. \(\text{CH}_3 - \text{CH} = \text{CH} - \text{CH}(\text{CH}_3) - \text{OH}\)

Hint:

Primary allylic alcohol: \(\text{CH}_2\text{-OH}\) next to double bond.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
An allylic alcohol is one where the hydroxyl group (\(-\text{OH}\)) is attached to an allylic carbon (an \(sp^3\) carbon adjacent to a carbon-carbon double bond). A primary alcohol is one where the hydroxyl-bearing carbon is attached to only one other carbon atom.
Step 2: Key Formula or Approach:
Structure of allylic group: \(\text{C=C-C-}\).
Primary allylic structure: \(\text{C=C-CH}_2\text{-OH}\).
Step 3: Detailed Explanation:
Let's analyze the options:
- (A) \(\text{H}_2\text{C=CH-CH(CH}_3\text{)-OH}\): The carbon with \(-\text{OH}\) is bonded to two other carbons. It is a secondary allylic alcohol.
- (B) \(\text{H}_2\text{C=CH-CH}_2\text{-OH}\): The carbon with \(-\text{OH}\) is bonded to only one other carbon (part of the double bond). This is a primary allylic alcohol (allyl alcohol).
- (C) \(\text{H}_2\text{C=CH-C(CH}_3\text{)}_2\text{-OH}\): The carbon with \(-\text{OH}\) is bonded to three other carbons. It is a tertiary allylic alcohol.
- (D) \(\text{CH}_3\text{-CH=CH-CH(CH}_3\text{)-OH}\): Similar to A, it is a secondary allylic alcohol.
Step 4: Final Answer:
The primary allylic alcohol is allyl alcohol, shown in option B.