Question

Which of the following compounds does not exhibit optical isomerism?

• A. 3-Iodohexane
• B. 2-Iodopentane
• C. 2-Iodo-2-methylbutane
• D. 2-Iodo-3-methylbutane

Hint:

To quickly spot achiral carbons, look for numbers repeating in the IUPAC name (e.g., 2-something-2-methyl) or identical alkyl groups on the branched carbon!

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A molecule exhibits optical isomerism if it contains at least one chiral carbon atom (a carbon bonded to four different groups).

Step 2: Formula Application:
Analyze the substituents on the carbon holding the Iodine: - (a) 3-Iodohexane: Attached to $H$, $I$, Ethyl, and Propyl (Chiral). - (b) 2-Iodopentane: Attached to $H$, $I$, Methyl, and Propyl (Chiral).

Step 3: Explanation:
In 2-Iodo-2-methylbutane, the 2nd carbon is attached to: 1. Iodine ($-I$) 2. Ethyl group ($-C_2H_5$) 3. Methyl group ($-CH_3$) 4. Another Methyl group ($-CH_3$) Since two groups are identical (methyl), the carbon is achiral.

Step 4: Final Answer:
2-Iodo-2-methylbutane does not exhibit optical isomerism.