Question

How many products (including stereoisomers) are expected from monochlorination of the following compound?
$CH_3-CH-CH_2-CH_3$

• A. 3
• B. 6
• C. 5
• D. 2

Hint:

When monochlorinating a compound with asymmetric carbons (especially secondary carbons), be sure to account for stereoisomers.

Answer 1

The Correct Option is A

Monochlorination involves substituting one hydrogen atom with a chlorine atom. We must analyze all potential chlorine substitution sites and determine if any of these substitutions generate a stereocenter.

1. Chlorination at C1: CH₂Cl-CH₂-CH₂-CH₃, resulting in 1-chlorobutane.

2. Chlorination at C2: CH₃-CHCl-CH₂-CH₃, yielding 2-chlorobutane. The C2 carbon becomes a chiral center, leading to two stereoisomers (enantiomers): (R)-2-chlorobutane and (S)-2-chlorobutane.

3. Chlorination at C3: CH₃-CH₂-CHCl-CH₃, which is structurally equivalent to 2-chlorobutane (identical to the product from C2 chlorination based on connectivity). This molecule also possesses a chiral center, again producing two stereoisomers: (R)-2-chlorobutane and (S)-2-chlorobutane.

4. Chlorination at C4: CH₃-CH₂-CH₂-CH₂Cl, which is 1-chlorobutane, the same product obtained from C1 chlorination.

Consequently, there are three unique monochlorinated products: 1-chlorobutane, (R)-2-chlorobutane, and (S)-2-chlorobutane. The total count of distinct products, including stereoisomers, is 3.