Final answer:
Butanone is achiral because it has a symmetrical molecular structure, meaning it has a plane of symmetry and does not have four different substituents on a single carbon atom, which is a requirement for chirality. Unlike conformations of butane or cis-trans isomers of 2-butene, butanone's symmetry prevents it from having non-superposable mirror images, thus it cannot be chiral.
Step-by-step explanation:
Butanone, also known as methyl ethyl ketone (MEK), is achiral because its molecular structure is symmetrical, meaning it has a plane of symmetry. This ketone has four carbon atoms and the functional group is located at the second carbon. The two sides on either end of the functional group are mirror images of each other, which allows for the possibility of superposition, and hence, the molecule cannot have non-superposable mirror images, so it does not have an enantiomer.
Chirality in organic molecules occurs when a carbon atom has four different substituents, leading to non-superposable mirror images, known as enantiomers. Since butanone does not meet this criterion due to its symmetrical structure, it is not chiral. Isomers, like conformations of butane and cis-trans isomers of 2-butene, are common in organic chemistry, contributing to the complexity and the three-dimensional nature of organic molecules.