How can you tell if a molecule is achiral?

A chiral compound, as determined by molecular structure analysis, has four different atoms or groups attached to its C atom; an achiral compound lacks this feature.

Through experimentation, it was discovered that chiral compounds, which exist as a pair of isomers, rotate plane polarized light either clockwise or counterclockwise.

Take caution, though, as no rotation will be seen in a 50:50 mixture of each isomer (a racemic mixture) because the two rotations will cancel each other out.

A molecule is achiral if it possesses a plane of symmetry or if it has an internal mirror image. This means that if the molecule can be divided into two halves that are identical when reflected across a plane, it is achiral. Additionally, molecules with a center of symmetry are also considered achiral. If a molecule lacks these characteristics and has chiral centers, it is chiral.