Question

Which of the following is tertiary benzylic alcohol?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Benzylic means the OH carbon touches the ring; tertiary means that carbon has three carbon neighbours.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A benzylic alcohol has its \(-\text{OH}\) on a carbon directly attached to the benzene ring. It is tertiary if that carbon is bonded to three other carbon atoms (one of them the ring carbon) and carries no hydrogen.

Step 2: Check each structure:
(A) is benzyl alcohol, \(\text{C}_6\text{H}_5\text{CH}_2\text{OH}\): the carbinol carbon bears two hydrogens, so it is primary.
(B) is 1-phenylpropan-1-ol: the carbinol carbon bears one hydrogen and is attached to the ring and an ethyl group, so it is secondary.
(C) is 1-phenylethanol: again the carbinol carbon bears one hydrogen with a methyl and the ring, so it is secondary.

Step 3: The keyed structure:
(D) is 2-phenylpropan-2-ol, \(\text{C}_6\text{H}_5\text{C(CH}_3)_2\text{OH}\). The carbinol carbon is attached to the ring and to two methyl groups, has no hydrogen, and carries the -OH group. So it is a tertiary benzylic alcohol.

Final Answer:
Structure (D), 2-phenylpropan-2-ol, is the tertiary benzylic alcohol. \[ \boxed{\text{(D)}} \]