Total number of isomeric compounds (including stereoisomers) formed by monochlorination of 2 -methylbutane is _______.

The monochlorination of 2-methylbutane can result in the formation of different isomeric compounds. Here's how you can calculate them:

1. Identify the different types of hydrogen atoms in the molecule. In 2-methylbutane, there are three types of hydrogen atoms:

   • 9 hydrogen atoms attached to the end methyl groups (3 on each methyl group)
   • 2 hydrogen atoms attached to the middle carbon atom
   • 1 hydrogen atom attached to the carbon atom next to the methyl group

2. Each type of hydrogen atom can be replaced by a chlorine atom to form a different isomer.

3. Replacing one of the 9 hydrogen atoms attached to the end methyl groups with a chlorine atom will give you 1 isomer.

4. Replacing one of the 2 hydrogen atoms attached to the middle carbon atom with a chlorine atom will give you another isomer.

5. Replacing the hydrogen atom attached to the carbon atom next to the methyl group with a chlorine atom will give you a third isomer.

6. However, the third isomer can exist in two different forms due to the presence of a chiral center, resulting in two stereoisomers.

So, the total number of isomeric compounds (including stereoisomers) formed by monochlorination of 2-methylbutane is 1 (from the end methyl groups) + 1 (from the middle carbon atom) + 2 (from the carbon atom next to the methyl group) = 4.