7.1.1 Crude Oil, Hydrocarbons and Alkanes

Crude oil is a valuable natural resource that is formed over millions of years from the remains of ancient marine organisms, primarily plankton, which accumulated at the bottom of oceans and lakes. The organic matter underwent decomposition and was buried under layers of sediment, leading to the formation of crude oil deposits trapped within rocks.

Crude oil is a complex mixture consisting of numerous different compounds. However, the majority of these compounds are hydrocarbons, which are molecules composed solely of carbon and hydrogen atoms. Hydrocarbons exhibit a wide range of physical and chemical properties, making them essential for various applications in industry, transportation, and energy production.

Among the hydrocarbons present in crude oil, the most abundant class is known as alkanes. Alkanes are saturated hydrocarbons, meaning they contain only single covalent bonds between carbon atoms. The general formula for the homologous series of alkanes is:

C_nH_2n+2

where "n" represents the number of carbon atoms in the molecule.

The first four members of the alkane series are methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀). Each alkane differs from the next by an additional methylene (-CH₂-) unit. For example, ethane has one additional carbon atom compared to methane, propane has two additional carbon atoms compared to ethane, and so on.

Alkane molecules can be represented as either a molecular formula (such as C₂H₆), or through a structural formula, which shows the arrangement of atoms and bonds in the molecule: