Here's a breakdown:
* Double bond: When referring to a double bond, "trans" means the substituents are positioned on different sides of the double bond plane. This creates a geometry where the substituents are as far apart as possible.
* Ring structure: In a ring structure, "trans" means the substituents are on opposite sides of the ring plane.
Example:
* Trans-2-butene: The two methyl groups are on opposite sides of the double bond.
* Trans-1,2-dimethylcyclohexane: The two methyl groups are on opposite sides of the cyclohexane ring.
Contrast with "cis":
The opposite of "trans" is "cis," which indicates that two substituents are located on the same side of a double bond or ring structure.
Importance:
The "trans" configuration significantly impacts the properties of molecules, including:
* Physical properties: Boiling point, melting point, and density.
* Chemical reactivity: How the molecule interacts with other molecules.
* Biological activity: How the molecule interacts with biological systems.
Note:
* The terms "trans" and "cis" are typically used in conjunction with other information to describe the specific molecule, such as the name of the molecule and the positions of the substituents.
* The terms "trans" and "cis" are sometimes replaced with the prefixes "E" and "Z" respectively, which are based on a more rigorous system of assigning priority to substituents.