See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: 1,2-Shift in Propylbenzene **Understanding the 1,2-Shift (Wagner-Meerwein Rearrangement):** A 1,2-shift involves migration of an alkyl group or hydrogen atom from one carbon to an adjacent carbon, typically to stabilize a carbocation intermediate. **Step 1: Initial Carbocation Formation** When propylbenzene ($CH_3-CH_2-CH_2$-Ph) undergoes ionization or hydration conditions, a carbocation forms at the benzylic position (carbon attached to benzene). **Step 2: Identify the 1,2-Shift** In a 1,2-shift: - A hydrogen atom from the adjacent $\beta$-carbon (the middle $CH_2$) migrates to the carbocation center - This creates a secondary carbocation at the $\beta$-carbon position **Step 3: Product Structure** After the 1,2-hydrogen shift: $$CH_3-CH_2-CH_2^+ \text{ (Ph)} \rightarrow CH_3-\stackrel{+}{CH}-CH_2\text{(Ph)}$$ The resulting structure is: **$CH_3-\stackrel{+}{CH}-CH_2-Ph$** This matches **option (C)**: A secondary benzylic carbocation with the positive charge on the internal carbon, flanked by a methyl group on one side and a phenylmethylene group on the other. **Why (C) is correct:** The 1,2-shift moves the positive charge one carbon away from the benzene ring, generating the rearranged carbocation shown in option C.