Difference Between Cis and Trans Isomers

Cis and Trans Isomerism is a type of geometric isomerism and can be found in both organic and inorganic compounds. Cis and trans isomers are stereoisomers that have the same chemical formula but are different in their structure. The words “cis” and “trans” originated from the Latin words “this side” and “the other side”, respectively which means in cis same group is on the same side, and in trans same group is on the other side.

In this article, we will learn about Cis and Trans Isomerism, their differences, and others in detail.

Difference Between Cis and Trans Isomerism

Difference between Cis and Trans isomerism is added in the table below,

Cis Isomerism Vs Trans Isomerism
	Cis Isomerism	Trans Isomerism
Definition	Isomers with similar groups on the same side of the molecule	Isomers with similar groups on opposite sides of the molecule
Geometry	Bent or curved structure	More linear or straight structure
Symmetry	Less symmetrical(Asymmetric)	More symmetrical(symmetry)
Stability	Less stable	More stable
Melting point	Lower melting point	Higher melting point
Boiling point	High boiling point	Low boiling point
Polarity	Polar	Non polar
Solubility	More soluble in polar solvent	Less soluble in polar solvent
Density	Denser	Less denser
Acid-base Properties	More acidic	Less acidic
Example	Cis-1,2-dimethylcyclohexane	Trans-1,2-dimethycyclohexane

Now let’s learn about Cis Isomerism and Trans Isomerism in brief

Cis Isomerism

Cis isomerism is a type of stereoisomerism where two identical groups are positioned on the same side of a non-rotatable bond(such as a double bond or ring structure) within a molecule. This arrangement creates an asymmetry structure, which affects the shape of molecules’ compounds and properties without changing their chemical formula.

Physical and Chemical properties: he physical and chemical properties of cis isomers can vary based on their molecular structure and the nature of compounds and they are added in the table below,

Geometry	A bent or curved shape, due to more steric hindrance
Symmetry	Less symmetrical shape(Asymmetrical)
Stability	Less stable due to steric hindrance
Melting Point	Due to more intermolecular space the molecule is loosely packed so melting point of cis isomer lower than trans
Boiling Point	Boiling point of cis is higher because of presence of strong forces of attraction between the atoms of cis isomer
Polarity	Cis isomers are mostly polar
Solubility	Cis isomer tends to be more polar than its trans isomer due to their bent shape and uneven electron distribution. This makes cis isomer more soluble in polar solvent like water or alcohol, As “like dissolves like”.
Density	Cis isomers are denser than their trans isomers, because same group lie on same side of non rotating bond, which results in bent and compact structure, this high’s mass per unit volume which means higher density
Acid-base Properties	Cis isomer is tends to be more acidic than trans isomer of same molecule due to slightly lower pKa value of cis isomer.

Trans Isomerism

Trans isomerism is a type of stereoisomerism where two identical groups are positioned on the opposite side of a non-rotatable bond(such as double bond or ring structure) within a molecule. This arrangement creates symmetry structure, which affect the shape of molecules compound and properties from its cis molecule without changing it’s chemical formula.

Physical and Chemical properties: The physical and chemical properties of cis isomers can vary on the basis of their molecular structure and the nature of compounds and they are added in the table below,

Geometry	More linear or straight shape, due to less steric hindrance.
Symmetry	More symmetrical shape(symmetrical).
Stability	More stable due to less steric hindrance.
Melting Point	Due to less intermolecular space the molecule is tightly packed so melting point of trans isomer higher than cis.
Boiling Point	Boiling point of trans is lower because of absence of strong forces of attraction between the atoms of trans isomer
Polarity	Trans isomers are mostly non-polar
Solubility	Trans isomer tends to be non-polar than its cis isomer due to their linear shape and even distribution of electron. This makes trans isomer less soluble in polar solvent like water or alcohol.
Density	Trans isomers are less denser than their cis isomers, because same group lie on opposite side of non-rotating bond, which results in linear and elongated structure, this increases spacing between groups decreases the molecule’s overall density.
Acid-base Properties	Trans isomer is tends to be less acidic than cis isomer of same molecule due to slightly higher pKa value of trans isomer.

Read More,

• Alkanes
• Alkenes
• Alkynes

Frequently Added Question on Cis and Trans Isomerism

What is Difference between Cis and Trans Isomers Energy?

In comparision of energy Cis isomer is found to have lower energy than trans isomer.

What is Difference between Cis and Trans Alkenes?

The general differnce between Cis and Trans Alkene is Cis Alkene are more polar than Trans Alkene.

What Methods are Used to Distinguish Between Cis and Trans Isomers?

Method used to distinguish between Cis and Trans isomers is, if the two group are present on the same side of the double bond in the molecule then it is cis isomers. If the two groups are present on the opposite side of the double bond then its is trans isomers.