Question

Identify the major product in the following reaction.

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is C

This is an E2 elimination reaction where the hydroxide ion acts as a strong base. The reaction proceeds as follows:
Step 1: Identify the base and leaving group
In the presence of \(\text{OH}^-\) and EtOH, the bromine atom (\(\text{Br}\)) is the leaving group. The hydroxide ion removes a proton (\(\text{H}^+\)) from an adjacent carbon, forming a double bond.
Step 2: Formation of the double bond
The E2 mechanism involves a single step for elimination. The base abstracts a \(\beta\)-hydrogen atom (from the carbon adjacent to the one bearing \(\text{Br}\)), and the \(\text{Br}^-\) departs, creating a double bond between the \(\alpha\)- and \(\beta\)-carbons.
Step 3: Determine the major product
The double bond forms between the \(\alpha\)-carbon (originally bonded to bromine) and the \(\beta\)-carbon. Zaitsev's rule dictates that the most substituted alkene is the major product. Therefore, the major product is cyclopentene with a methyl (\(\text{CH}_3\)) substituent.
Final Answer: (3) Cyclopentene with a \(\text{CH}_3\) substituent.