Isomer, << EYE suh muhr, >> is any of two or more chemical compounds with the same number of each kind of atom but a different arrangement of those atoms. Isomers generally differ from one another in both their physical properties and their chemical behavior.
For example, normal butane and isobutane are two isomers of the compound butane. The two isomers have the same chemical formula, C4H10. But normal butane has its four carbon atoms linked in a chain, and isobutane has a branching structure. As a result, normal butane and isobutane have different boiling points. Normal butane boils at –0.5 °C, but isobutane boils at –12 °C.
The structure of some compounds lacks symmetry, the ability to be divided into two identical halves. Such compounds are called chiral compounds. These compounds have isomers that are mirror images of each other, much like a person’s left and right hand. The two isomers of a chiral compound are called enantiomers. The two enantiomers of a chiral compound have the identical physical properties of density, melting point, and boiling point. But often, living things can use only one chiral isomer of a compound for a particular task.
