Introduction to Hydrocarbons - What are hydrocarbons?

What are hydrocarbons?

Hydrocarbons are a group of organic compounds that contain only carbon and hydrogen. Hydrocarbons can be basically considered as hydrides of the carbon. Hydrocarbon compounds can categorized into different categories based on their structures, configurations, and bonds.

Classification of hydrocarbon compounds

According to the structure of the compounds, hydrocarbon compounds are classified into two main groups and they are:

• Aliphatic Hydrocarbons
• Aromatic Hydrocarbons

I. Aliphatic Hydrocarbons

Aliphatic hydrocarbon compounds can be either cyclic or acyclic and do not contain any delocalized pi-electron cloud.

Acyclic aliphatic hydrocarbon compounds can be categorized into three groups, which are:

• Alkanes - Contains only sigma bonds (no double or triple bonds)
• Alkenes - Contains at least one carbon-carbon double bond
• Alkynes - Contains at least one carbon-carbon triple bond

Cyclic aliphatic hydrocarbon compounds can be categorized into three groups, which are:

• Cycloalkanes - Closed chain / cyclic molecule with only sigma bonds
• Cycloalkenes also known as cycloolefin - Closed chain / cyclic molecule (not an aromatic ring) with at least one double bond.
• Cycloalkynes - Closed chain / cyclic molecule (not an aromatic ring) with at least one triple bond. To form a cycloalkyne, the number of carbon atoms needs to be sufficient enough to allow the flexibility that is needed to fulfill the geometry of the molecule. The smallest stable cycloalkyne is cyclooctyne (C₈H₁₂)

II. Aromatic Hydrocarbons

Aromatic hydrocarbon compounds are cyclic compounds that have been stabilized by a delocalized Pi electron cloud. The simplest aromatic hydrocarbon is benzene (C₆H₆). Also, aromatic hydrocarbon compounds can be monocyclic or polycyclic. Naphthalene is one example of a polycyclic hydrocarbon.

The hydrogen atoms can be substituted by alkyl groups to form substituted aromatic hydrocarbon compounds. Toluene is an example of this.