What are Hydrocarbons?

Hydrocarbons are organic compounds whose molecular structure is formed from the union between hydrogen and carbon atoms.

The formula basis of hydrocarbons is as follows: CxHY.

These organic compounds can be found in different states of matter: liquid, gaseous (natural gas or by condensation) and eventually solid.

The Petroleum (in liquid state) and the natural gas (in gaseous state) are mixtures of hydrocarbons. Hydrocarbons are the source from which other organic substances are derived, such as fossil fuel.

Characteristics of hydrocarbons

  • They are organic compounds made up of carbon and hydrogen atoms only.
  • They are not usually biodegradable.
  • They are hydrophobic, that is, insoluble in water.
  • They are lipophilic, that is, soluble in organic solvents.
  • When combustion is optimal or complete, they produce water and carbon dioxide.
  • When combustion is inadequate or incomplete, they produce water and carbon or carbon monoxide (soot).

Classification of hydrocarbons

There are two main types of hydrocarbons. Let’s look at each one separately.

Aromatic hydrocarbons or arenes

They are organic compounds cyclical characterized by having a common nucleus, known as benzene. It can be of two kinds:

  • monocyclic: those in which a hydrogen molecule of the benzene ring is replaced by side chains, that is, by hydrocarbon residues. For example, Methylbenzene or Toluene (C6H5-CH3).
  • polycyclic: are those that contain two or more benzene nuclei.
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Aliphatic hydrocarbons

They are essentially made up of hydrogen and carbon and are not aromatic in character. Their chains are open, and can be both linear and branched. Aliphatic hydrocarbons are subdivided into:

  • Saturated hydrocarbons or alkanes: are those whose carbon bonds are simple. Alkanes contain carbon-carbon single bonds. The general formula for alkanes is as follows: (CnH2n+2) For example, the ethane.
  • unsaturated hydrocarbons: are those that contain double or triple carbon-carbon bonds. They are part of this group:
    • Alkenes or olefins: with carbon-carbon double bonds (CHtwo=CHtwo). For example: Limonene (from citrus oils).
    • alkynes or acetylenes (with carbon-carbon triple bonds). For example: ethyne (HC≡CH).

Where do hydrocarbons come from?


Hydrocarbons are usually found in deposits, deposits or reservoirs at the subsoil level, either on the terrestrial platform or on the marine platform.

The process that results in obtaining hydrocarbons consists of four stages. Let’s meet them.

1. Sedimentation at great depth

Hydrocarbons are formed from the decomposition and thermal transformation of sediments of organic matter (algae, remains of plants, animals) deposited at great depths, which are contained in the so-called bedrockthat is, in the rocky base of the ground.

2. Heating and pressure

The concentration of temperature and pressure exerted on organic matter over the centuries causes it to transform into liquid (petroleum) or gas. The transformation of organic matter depends on the presence of the parent rock.

3. Migration of hydrocarbons from the source rock to the reservoir rock

Once transformed, the hydrocarbons migrate towards the pores of the so-called warehouse rocks, that is, sand and fragmented rocks that can absorb and expel fluids. Storage rocks have two characteristics: porosity and permeability. It is not, therefore, a concave deposit as is usually imagined.

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4. Retention by oil trap or impermeable rocks

Is named oil trap to the geometric shape of a reservoir rock where the fluid is trapped. The trap is covered by a seal rock that prevents the hydrocarbon in question from being expelled to the surface.

See also: Petroleum and Organic Compounds.

Use and importance of hydrocarbons

Other important substances are formed from hydrocarbons, without which modern and industrial life as we know it would not be possible.

Hydrocarbons have, in fact, many uses both at the industrial level and in everyday life, since from them it is obtained:

  • Energetic resources: refers to fuels from hydrocarbons that allow the mobilization of industry, transport, agriculture and electricity for domestic consumption. This is equivalent to almost 80% of the electricity generation in the world.
  • Raw Materials: useful in the manufacture of products such as plastic, inks, rubber, synthetic fibers for textiles, detergents, pencils, insecticides and chemical products in general.
  • Special products: These include asphalt, equipment and motor greases, lubricants, paraffins, etc.

See also Fossil fuel.

Substituted hydrocarbons

It refers to those compounds that, although they share the same basic structure of a hydrocarbon, also contain atoms of other chemical elements. That section of the molecule with these characteristics is called a functional group.

For example:

Halogenated compounds such as those included in pesticides, repellents, solvents or refrigerants.