Difference Between Between Cis and Trans Isomers

When we are studying isomers in chemistry, we will come across various types of isomers. While they are mainly divided into two groups namely constitutional isomers and stereoisomers there are more sub-type of isomers that we need to learn about. As such, cis and trans isomers are such types of isomers which we will learn about here on this page. We’re going to research what these isomers are and the main distinctions between cis and trans.

Usually, cis and trans isomerism can be found in organic and inorganic compounds, alkanes and in alkenes.

The isomers in which two similar atoms or groups of atoms lie on the same side of a double bond are stated as cis isomers. whereas the isomers in which two similar atoms or groups of atoms lie anti to each other of a double bond are stated as trans-isomers. Cis and trans isomers have the same molecular formula and molecular weight, but they are known to differ in some aspects.

Difference Between Cis and Trans Isomers

When we talk about the difference between cis and trans isomers, one of the main differences is in the arrangement of the atoms in a double bond. However, we will look at some other key differences between the two below.

Difference Between Cis and Trans Isomers
Cis Trans
Cis isomers are molecules with the same connectivity of atoms. They feature same side groups placed on the same side of a double bond. Trans isomers feature molecules with same side groups placed on opposite sides of a double bond.
Cis isomers are almost always polar. Trans isomers are not very polar. Many trans isomers are non-polar molecules.
Due to loosely packed molecules, cis isomers have relatively lower melting points than trans isomers. Due to tightly packed molecules, the melting points of trans isomers are usually higher than those of cis isomers.
The boiling point of cis isomers is high due to the presence of strong forces of attraction between the atoms of the cis isomer. The boiling point is comparatively low for trans isomers as there are no strong attractive forces.
Cis isomers in inert solvents have a strongly soluble content. A solubility in neutral solvents is smaller.
Both forms of isomers have higher acid power. The protons aren’t readily emitted in trans isomers. So it has less acidic strength.

cis trans

These are some differences between cis and trans isomers. To know more about isomers and other chemistry topics you can keep visiting BYJU’s or download our app for interesting content and learning experience.

Related Links:

Isomerism Stereochemistry
Difference between Allotropes and Isomers Isomerism In Coordination Compounds


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  1. Which of the cis and trans isomers is at the higher energy state?

    • Trans isomer is always stable and exist at lower energy state. On the other hand cis isomer is at higher energy state and unstable.