Introduction

Hydrocarbons are any organic compounds that contain only carbon and hydrogen

Hydrocarbons are energy-rich because of their high carbon content. They are burned in oxygen (combustion) to release their energy.

Crude oil, or petroleum, is the main source of liquid hydrocarbons. Crude oil is a mixture of various hydrocarbons, which can be separated via fractional distillation.

These components have distinct uses, from providing energy for cooking to lubricating machine parts.

Natural gas mainly contains methane, which is the smallest hydrocarbon.

Crude oil and natural gas formed over the course of millions of years from decomposed plants and animals buried underground.

Oil, natural gas and coal (which consists of carbon and various other elements) are fossil fuels

Classification of Aliphatic Hydrocarbons

There two major classes of hydrocarbons: These are aliphatic and aromatic hydrocarbon

Aliphatic hydrocarbons made up of straight chains, branching chains, or rings that do not contain delocalized bonds

Aliphatic hydrocarbons can be divided up into two classes:

• Alicyclic hydrocarbons have carbon chains in which the two ends of the chain are joined to make a ring.
• Acyclic hydrocarbons have straight or branching carbon chains, but no rings.

Aliphatic hydrocarbons also can be classified as to whether they contain only single bonds (saturated hydrocarbon) or if they contain more than a single bond such as double bonds or triple bonds (unsaturated hydrocarbon). Multiple bonds alter the bond geometry around the carbons. A carbon with 4 single bonds has a tetrahedral arrangement of bonds, a carbon with a double bond has a planar triangular arrangement of bonds. This changes the geometry and structure of the whole molecule.

Multiple bonds also alter the ability of the molecule to rotate around a carbon-carbon bond, that is, multiple bonds cannot rotate.

Alkanes: Contain only single carbon-carbon bonds. They have the general formula C_nH_2n+2

Alkenes: Contain at least one double carbon-carbon bond, but no triple bonds. They have the general formula C_nH_2n

Alkynes: Contain at least one triple carbon-carbon bond. They have the general formula C_nH_2n-2

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Hydrocarbons