Question

Number of isomeric products formed by monochlorination of 2-methylbutane in presence of sunlight is _______.

Answer 1

Correct Answer: 6

To determine the number of isomeric products formed by monochlorination of 2-methylbutane under sunlight, we must identify the distinct hydrogen atoms that can be substituted by chlorine. 2-Methylbutane, also known as isopentane, has the structural formula:

         CH₃
           |
CH₃-CH-CH₂-CH₃
           |
           CH₃

There are four types of hydrogen atoms in the molecule based on their attached carbon's degree: primary (1°) hydrogens on the terminal methyl groups, secondary (2°) hydrogens on the methylene group, and a tertiary (3°) hydrogen on the central carbon. Analyzing these positions allows us to identify the unique monochlorinated products:

1. Chlorination at a primary hydrogen on a terminal methyl group yields 1-chloro-2-methylbutane. There are two such methyl groups, but they are structurally equivalent, leading to one distinct product from this position.
2. Chlorination at the secondary hydrogen on the methylene group forms 3-chloro-2-methylbutane.
3. Chlorination at the tertiary hydrogen on the central carbon forms 2-chloro-2-methylbutane.

Collectively, these reactions produce 3 distinct constitutional isomers:

Hydrogen Type	Position in 2-Methylbutane	Product
1°	Terminal methyl (CH3)	1-chloro-2-methylbutane
2°	Methylene (CH2)	3-chloro-2-methylbutane
3°	Central tertiary carbon (CH)	2-chloro-2-methylbutane

Therefore, there are 3 distinct isomeric products. The initial text contained an error in counting. The corrected number of distinct constitutional isomers is 3.