Question

How do optical isomers exist?

Answer 1

How? You might have to restate your question.

Explanation:

See this older answer. A carbon centre with four different groups attached to it, i.e. `CR_1R_2R_3R_4` is necessarily chiral, and can exist as 2 stereoisomers, where the one is the mirror image of the other. The stereoisomers cannot be superimposed.