What are the differences between cis- and trans-isomers?
http://en.wikipedia.org/wiki/Cis%E2%80%93trans_isomerism
Cis-isomers and trans-isomers are two types of geometric isomers that differ in the arrangement of atoms or groups around a double bond or a cyclic structure. To understand the differences between cis- and trans-isomers, you need to consider the following:
1. Definition: Cis-isomers refer to molecules where the identical or similar groups are on the same side of the double bond or cyclic structure. Trans-isomers, on the other hand, have the identical or similar groups on the opposite sides of the double bond or cyclic structure.
2. Molecular symmetry: Cis-isomers tend to have less symmetry compared to trans-isomers. This is because cis-isomers have a distinct arrangement of groups on one side of the molecule, while trans-isomers have a symmetrical arrangement of groups on both sides.
3. Physical properties: Cis-isomers and trans-isomers often exhibit different physical properties. For example, their melting points, boiling points, and densities can vary due to differences in molecular shape and intermolecular forces.
4. Chemical reactivity: The arrangement of atoms or groups in cis- and trans-isomers can influence their chemical reactivity. These isomers may show different behavior when reacting with other molecules or undergoing chemical transformations.
To determine whether a molecule is a cis-isomer or a trans-isomer, you can visually inspect its structure and identify the arrangement of atoms or groups around the double bond or cyclic structure. Additionally, you can use spectroscopic techniques like NMR (nuclear magnetic resonance) or X-ray crystallography to obtain more precise information about the molecular arrangement.
Understanding the concepts of geometric isomerism, molecular structure, and spectroscopic techniques can help you identify and distinguish between cis- and trans-isomers.