Isomer: meaning, definitions and examples

General term used to refer to molecules with the same molecular formula but different structures.

• Isomers have different physical and chemical properties from each other

Isomers that differ in the connectivity of their atoms, meaning their chemical structure is arranged differently.

• Butane and isobutane are examples of structural isomers

General term for isomers that have the same structural formula but differ in the arrangement of atoms in space.

• Stereochemists study the three-dimensional arrangement of molecules, especially focusing on stereoisomers

Specifically refers to isomers that differ in the spatial arrangement of groups around a double bond or ring structure.

• The compound can exist as geometric isomers, with the cis and trans forms having different properties

Use this term when referring to molecules that have the same molecular formula but different structures or arrangements of atoms.

• Glucose and fructose are isomers of each other.

Optical isomers are a type of stereoisomer that can rotate plane-polarized light. This term is especially useful when the focus is on the optical activity of the molecules.

• Many drugs have optical isomers that can have vastly different effects in the body.

Employ this word when discussing stereoisomers that are non-superimposable mirror images of each other. Enantiomers often have identical physical properties except for their optical activity.

• D-glucose and L-glucose are enantiomers, differing in their ability to rotate plane-polarized light.

This term is appropriate when talking about stereoisomers that are not mirror images of each other. Diastereomers have different physical properties and different reactivity.

• Mannose and galactose are diastereomers because they are not mirror images and have different properties.