Question

The major product of the reaction is

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

The reaction under consideration involves the substitution of bromine in a compound using sodium iodide (NaI) in methanol as the solvent at an elevated temperature of 110°C. This reaction is a typical example of a Finkelstein reaction, which is an SN2 reaction commonly used to exchange one halide for another.

In this specific reaction, NaI in methanol is used to replace the bromine atoms in the substrate with iodine atoms. The SN2 mechanism is characterized by the nucleophilic substitution where the incoming nucleophile attacks an electrophilic carbon with the departure of the leaving group—in this case, bromine.

Let's analyze the steps:

1. Substrate Analysis: The substrate contains two vicinal bromine atoms on a cyclohexane ring. Bromine-82 is indicated as Br^*.
2. Nucleophile: Iodide ion (I^-) from NaI acts as the nucleophile.
3. Leaving Group: Bromide ion (Br^-) is the leaving group.
4. Mechanism:
   • The iodide ion attacks the carbon bonded to bromine, simultaneously displacing the bromine atom.
   • The reaction replaces the bromine with an iodine atom in a one-step concerted mechanism.
   • Due to the conditions (110°C), an elimination to form an alkene is less favorable than substitution.
5. Major Product: The major product is the compound where bromine atoms are replaced by iodine atoms.

Given the options provided, the correct major product can be identified as:

This product is consistent with the Finkelstein reaction conditions and the substitution of bromine with iodine. Moreover, iodine is observed to substitute more stereospecifically via the backside attack typical in SN2 reactions.

In conclusion, the major product results from the nucleophilic substitution where bromine is replaced by iodine, leading to the correct answer choice shown above.