The key difference between conjugated and isolated double bond is that conjugated double bond refers to an organic structure having alternating double bonds and single bonds, whereas isolated double bond refers to an organic structure where there are no alternating double and single bonds and the double bonds are in a random arrangement.
The term double bond in chemistry refers to a structure where two atoms are bonded to each other through a sigma bond and a pi bond. In organic chemistry, double bonds are an important feature in organic compounds where there is a sigma bond and a pi bond between two carbon atoms.
CONTENTS
1. Overview and Key Difference
2. What is Conjugated Double Bond
3. What is Isolated Double Bond
4. Conjugated vs Isolated Double Bond in Tabular Form
5. Summary – Conjugated vs Isolated Double Bond
What is Conjugated Double Bond?
Conjugated double bonds are two or more double bonds that are separated by single bonds. In other words, if there are more than two double bonds in a chemical structure, these double bonds are arranged in an alternating pattern with the single bonds.
A conjugated system of double bonds and single bonds cause the formation of a conjugated system having delocalized electrons. This means the conjugated system has electrons spread throughout the conjugated system rather than existing in fixed positions on the double bond. This is called delocalization. This delocalization usually lowers the energy level of the structure, thereby increasing the stability of the structure. Conjugated double bonds can occur in ring structures, acyclic structures, linear structures, or mixed structures having cyclic and linear structures.
The term conjugation refers to the mixing or overlapping of p orbitals of one atom with another p orbital in an adjacent sigma bond. Therefore, a conjugated system has a region where p orbitals overlap with each other.
What is Isolated Double Bond?
An isolated double bond is a chemical bond that is made of a sigma bond and a pi bond. Usually, this term is used when the double bonds in an organic structure are not arranged in an alternating pattern with the single bonds. In other words, isolated double bonds have two or more single bonds between them and are arranged in a random manner.
Therefore, these double bonds tend to take part in chemical reactions exactly as if there is one double bond in the compound. Here, unlike in conjugated systems, there is no electron delocalization taking place. This is because the double bonds are separated from each other, and there is no possibility for the overlapping of the p orbitals.
What is the Difference Between Conjugated and Isolated Double Bond?
Conjugated and isolated double bonds are two types of double bonds. The key difference between conjugated and isolated double bond is that conjugated double bond means an organic structure having alternating double bonds and single bonds, whereas isolated double bond means an organic structure where there are no alternating double and single bonds and the double bonds are in a random arrangement.
The below infographic lists the differences between conjugated and isolated double bond in tabular form for side by side comparison.
Summary – Conjugated vs Isolated Double Bond
Conjugated and isolated double bonds are two types of double bonds. The key difference between conjugated and isolated double bond is that conjugated double bond means an organic structure having alternating double bonds and single bonds, whereas isolated double bond means an organic structure where there are no alternating double and single bonds and the double bonds are in a random arrangement.
Reference:
1. “14.5: Two NEIGHBORING DOUBLE Bonds: Conjugated Dienes.” Chemistry LibreTexts, Libretexts, 14 July 2020.
Image Courtesy:
1. “1,3-pentadien” By Cäsium137 (D.) – Own work (Original text: selbst erstellt) (Public Domain) via Commons Wikimedia
2. “Diazomethane-pi-system” By Ben Mills – Own work (Public Domain) via Commons Wikimedia