Click image for a video examining the relationship of the molecular model with its mirror image. No matter how we rotate the mirror image in space, it does not superimpose with the original object. The two structures are not identical and they are chiral. Chiral objects are not identical to their mirror images. The property that distinquishes chiral objects from achiral ones is a plane of symmetry.
Achiral objects have a plane of symmetry that cuts the object into two identical halves.
We have seen that a molecule with a carbon atom bonded to three different groups is achiral. Consider 2-propanol and its mirror image. One skill students of organic chemistry need to develop is the ability to manipulate three dimensional objects. To compare the mirror image of 2-propanol to the original, you can rotate one object by 180 o to align two groups then superimpose the structure with the original object. They are superimposable and represent the same molecule.