Hi Dhanesh,

There are 4 structural isomers of 2 - methyl butane

• 1-Chloro-2-methylbutane
• 2-chloro-2-methylbutane
• 3-chloro-2-methylbutane
• 4-chloro-2-methylbutane

and 2 optical isomers -

• by chlorination at carbon no. 2
• by chlorination at carbon no. 3

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!