Predict the major, organic product for the following reaction.

• A.
• B.
• C.
• D.

Answer: (B)

Verified step by step guidance

1. Identify the type of reaction: The reaction involves an alkyl halide (1-iodopropane) and an aromatic compound (ethylbenzene) in the presence of a Lewis acid catalyst (FeBr3). This suggests a Friedel-Crafts alkylation reaction.
2. Determine the directing effects: The ethyl group on the benzene ring is an ortho/para-directing group due to its electron-donating nature. This means the incoming alkyl group will preferentially add to the ortho or para positions relative to the ethyl group.
3. Generate the electrophile: The FeBr3 catalyst will interact with the iodine in 1-iodopropane to form a more reactive electrophile, likely a carbocation or a complex that resembles a carbocation.
4. Consider the stability of the carbocation: The primary carbocation formed from 1-iodopropane can undergo rearrangement to a more stable secondary carbocation if possible, but in this case, it remains primary.
5. Predict the major product: The primary carbocation will attack the ortho or para position of the ethylbenzene. Given steric and electronic factors, the para position is often favored, but both ortho and para products can form. The major product is likely the para-substituted ethylbenzene with a propyl group.