Optical isomers (enantiomers) are not found in CH2ClBr because it lacks a chiral center.

Here's why:

* Chiral center: A chiral center is a carbon atom that is bonded to four different groups. This creates a non-superimposable mirror image, which is the basis for optical isomerism.

* Structure of CH2ClBr: The central carbon atom in CH2ClBr is bonded to two hydrogen atoms, one chlorine atom, and one bromine atom. Since it has two identical hydrogen atoms attached, it does not meet the requirement of four different groups.

In summary: The lack of a chiral center in CH2ClBr prevents it from having optical isomers.