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

Concept:

• Allylic alcohol: –OH group attached to carbon adjacent to a double bond
• Primary alcohol: –OH bearing carbon attached to only one carbon

Step 1: Check allylic position. All options contain double bond, so check position of –OH relative to double bond.
Step 2: Check degree of alcohol.

• (A) Carbon with –OH attached to two carbons → secondary $\times$
• (B) \(\text{CH}_2\text{-OH}\) attached to one carbon → primary \checkmark
• (C) Carbon with –OH attached to three carbons → tertiary $\times$
• (D) Carbon with –OH attached to two carbons → secondary $\times$

Step 3: Conclusion. Only option (B) is primary allylic alcohol.