10 Difference Between Cis And Trans Isomers (Cis Vs Trans)

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Two molecules are isomers if they contain the exact same number and types of atoms, with just a different arrangement or rotation around a chemical bond. Molecules are not isomers if they have a different number of atoms or different types of atoms from each other.

Cistrans isomerism also referred to as Geometric Isomerism or Configurational Isomerism, is a term used in organic chemistry. The Prefixes “Cis’’ and ‘’Trans’’ are from Latin, meaning ‘’on the same side of ’’ and ‘’ on the opposing side of’’ respectively. In chemistry, Cis indicates that the functional groups are on the same side of the carbon chain while Trans conveys that functional groups are on opposing sides of the carbon chain. Cistrans isomers are stereoisomers, that is, pairs of molecules which have the same formula but whose groups are rotated into a different orientation in three-dimensional space.

Trans isomers are isomers having the same connectivity of atoms and are composed of identical side groups that can be found on the opposite sides whereas Cis isomer is an isomer where two of the same atoms are on the same side of the double bond in a molecule. Cis-trans nomenclature describes the relative position of the substitutes and does not provide a stereochemical description as the E, Z-nomenclature, applicable only for the alkenes.

Typically, Cis and trans display different chemical and physical properties; and can be found in both organic and inorganic compounds, alkenes and alkanes. They also have same molecular formula and molecular weight; but have different geometry.

What You Need To Know About Cis Isomers

  1. The prefix “Cis’’ is derived from Latin, meaning ‘’on the same side of’’.
  2. Cis isomers are molecules having the same connectivity of atoms and are composed of identical side groups that can be found on the same side.
  3. The Cis isomer is always a polar molecule.
  4. The melting point of Cis isomers is comparatively low due to the loose packing of molecules.
  5. The boiling point of Cis isomers is comparatively high due to the presence of strong intermolecular forces.
  6. Cis isomers are highly soluble in inert solvents.
  7. Cis isomers have higher acidic strength.
  8. These types of isomers are less symmetrical.
  9. In the Cis isomer, the substituent groups are placed on one side of a double bond plane.
  10. In acyclic systems, the Cis isomers are comparatively more unstable.

What You Need To Know About Trans Isomers

  1. The prefix ‘’trans’’ is derived from Latin, meaning ‘’on opposing side of”.
  2. Trans isomers are molecules having the same connectivity of atoms and are composed of identical side groups that can be found on the opposite sides.
  3. The Trans isomer is less polar or nonpolar.
  4. The melting point of trans isomers is comparatively high due to tight packing of molecules.
  5. The boiling point of trans isomer is comparatively low due to the absence of strong intermolecular forces.
  6. Trans isomers are less soluble in inert solvents.
  7. In trans isomers, the protons are not easily released, therefore they are less acidic.
  8. These type of isomers are more symmetrical.
  9. In the trans isomer, the substituent group are placed on different sides of a double bond plane or a non-aromatic cycle.
  10. In acyclic systems, the trans isomers are comparatively less unstable.

Difference Between Cis And Trans Isomers In Tabular Form

BASIS OF COMPARISON Cis Isomers Trans Isomers
Name Origin The prefix “Cis’’ is derived from Latin, meaning ‘’on the same side of’’.   The prefix ‘’trans’’ is derived from Latin, meaning ‘’on opposing side of”.  
Description They are molecules having the same connectivity of atoms and are composed of identical side groups that can be found on the same side.   They are molecules having the same connectivity of atoms and are composed of identical side groups that can be found on the opposite sides.  
Polarity They are always a polar molecule.   They are less polar or nonpolar.  
Melting Point The melting point of Cis isomers is comparatively low due to the loose packing of molecules.   The melting point of trans isomers is comparatively high due to tight packing of molecules.  
Boiling Point The boiling point of Cis isomers is comparatively high due to the presence of strong intermolecular forces.   The boiling point of trans isomer is comparatively low due to the absence of strong intermolecular forces.  
Solubility In Inert Solvents They are highly soluble in inert solvents.   They are less soluble in inert solvents.  
Acidity They have higher acidic strength.   The protons are not easily released, therefore they are less acidic.  
Symmetry These types of isomers are less symmetrical.   These types of isomers are more symmetrical.  
Substituent Groups The substituent groups are placed on one side of a double bond plane.   The substituent groups are placed on different sides of a double bond plane or a non-aromatic cycle.  
Acyclic Systems In acyclic systems, the Cis isomers are comparatively more unstable.   In acyclic systems, the trans isomers are comparatively less unstable.  

Also Read: Difference Between Protic And Aprotic Solvent

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