The key difference between acyclic and cyclic organic compounds is that acyclic compounds are linear compounds, whereas cyclic compounds are non-linear compounds.
Acyclic and cyclic compounds in organic chemistry are the two major types of compounds that are categorized based on their chemical structure. Most acyclic organic compounds have cyclic isomers. Therefore, we name linear or acyclic compounds using the prefix “n-”.
CONTENTS
1. Overview and Key Difference
2. What are Acyclic Organic Compounds
3. What are Cyclic Organic Compounds
4. Side by Side Comparison – Acyclic vs Cyclic Organic Compounds in Tabular Form
5. Summary
What are Acyclic Organic Compounds?
Acyclic organic compounds are chemical compounds having a basic linear structure. These are also known as open-chain compounds. These are linear structures rather than cyclic structures. Moreover, if there are no side chains attached to this acyclic compound, they are straight chain compounds. All these molecules are aliphatic compounds.
Most simple compounds in organic chemistry, including alkanes and alkenes, have both acyclic and cyclic isomers. Most cyclic structures of these compounds tend to be aromatic, having stable structures. Moreover, in the organic compounds having more than four carbon atoms per molecule, the acyclic molecule usually has straight-chain or branched-chain isomers. When naming these compounds, we can use the prefix “n-” in order to denote the straight-chain isomer. E.g. n-butane is the straight-chain butane molecule.
Figure 01: Structure of N-nonane
Straight chain molecules are not straight always since these molecules have bond angles that are often not 180 degrees. However, the term linear in this context refers to the schematically straight molecular structure. E.g. straight-chain alkenes usually have a wavy or “puckered” conformation rather than a straight structure.
What are Cyclic Organic Compounds?
Cyclic organic compounds are chemical compounds having a basic non-linear structure. In other words, these are ring structures. One or more series of atoms in the compound is connected to form a ring structure.
Figure 02: Non-Aromatic Cyclic Compounds
There are different sizes of rings, depending on the number of atoms involved in the ring formation. Moreover, there are cyclic organic compounds where all the atoms in the ring structure are carbon atoms and ring structures containing both carbon and other atoms such as oxygen and nitrogen atoms. Further, these cyclic compounds can be either aromatic or non-aromatic. Aromatic cyclic compounds contain a ring structure with alternating single and double/triple bonds, which makes a delocalized pi-electron cloud and makes the compound unsaturated. Non-aromatic cyclic compounds, on the other hand, contain either only single bonds or both single and double/ triple bonds in a non-alternating pattern.
What is the Difference Between Acyclic and Cyclic Organic Compounds?
In the organic chemistry, cyclic and cyclic compounds are the two main groups of compounds that are categorized based on the basic structure of the molecule. The key difference between acyclic and cyclic organic compounds is that acyclic compounds are linear compounds, whereas cyclic compounds are non-linear compounds. All acyclic organic compounds are non-aromatic compounds, but cyclic organic compounds can be either aromatic or non-aromatic compounds.
Below infographic shows the differences between acyclic and cyclic organic compounds in tabular form.
Summary – Acyclic vs Cyclic Organic Compounds
Acyclic and cyclic compounds are the two main groups of compounds that are categorized based on the basic structure of the molecule. The key difference between acyclic and cyclic organic compounds is that acyclic compounds are linear compounds, whereas cyclic compounds are non-linear compounds.
Reference:
1. “Acyclic compounds”. Glossary of Class Names of Organic Compounds and Reactive Intermediates Based on Structure. Available here.
Image Courtesy:
1. “Nonane 3D ball” By Jynto (talk) – Own work This image was created with Discovery Studio Visualizer (CC0) via Commons Wikimedia
2. “First four cycloalkanes” By Pete Davis – Own work (Public Domain) via Commons Wikimedia