Hydrocarbons

Hydrocarbons

What are Hydrocarbons?

Hydrocarbons are one of the major components of organic chemistry. They are organic compounds which are made up of hydrogen and carbon atoms. The molecular formula for these compounds is CxHy. The above-mentioned compounds play a vital role in daily life and most of them occur in nature.

The major part of fossil fuels is made up of these organic compounds. Their existence is seen in plants and trees. For example, Carotenes is an organic pigment which is found in green leaves and carrots. These hydrogen and carbon compounds make up to 98 percent of natural crude rubber. Further, they possess large internal energy which renders them their importance.

Hydrocarbons

Classification and Types of Hydrocarbons

Older chemists basically classified hydrocarbons as either aliphatic or aromatic. The classification was done on the basis of their source and their properties. As such, it was found out that Aliphatic hydrocarbons were derived from chemical degradation of fats or oils whereas Aromatic hydrocarbons contained substances that were a result of chemical degradation of certain plant extracts. However, today the compounds are distinguished on the basis of structure and not merely on the origin.

Besides, organic compounds are classified into:

  • Saturated hydrocarbons: They are the compounds in which carbon-carbon atoms and carbon-hydrogen atoms are held together by single bonds. These single bonded compounds are the simplest hydrocarbons. The general formula for these single bonded organic compounds is CnH2n+2.
  • Unsaturated hydrocarbons: These compounds consist of a single, double or a triple bond between carbon-carbon atoms. The double-bonded compounds are called alkenes and the triple bonded compounds are called alkynes. The general formula for alkenes is CnH2n and for alkynes the general formula is CnH2n-2.
  • Cycloalkanes: These hydrocarbons possess one or multiple carbon rings. The hydrogen atom is attached to the carbon ring.
  • Aromatic Hydrocarbons: These are also called as arenes. Arenes are compounds which consist of at least one aromatic ring.

Properties of Hydrocarbons

As a result of having a different molecular structure, the empirical formula of hydrocarbons is also different from each other. For instance, in linear alkanes, alkynes or alkenes, the amount of bonded hydrogen decreases in alkenes and alkynes. This is mainly due to the “self-bonding” or catenation of carbon that prevents the complete saturation of the hydrocarbon by the formation of double or triple bonds. The ability of hydrocarbons to bond to themselves is known as catenation. With such capabilities, hydrocarbons can form more complex molecules like cyclohexane and in rare instances aromatic hydrocarbons like benzene.

Meanwhile, cracking of Hydrocarbons is a process in which heavy organic molecules are broken down into lighter molecules. This is accomplished by supplying an adequate amount of heat and pressure. Sometimes catalysts are used to speed up the reaction. This process plays a very important role in the commercial production of diesel fuel and gasoline.

Uses of Hydrocarbons

  • Hydrocarbons are widely used as fuels. For example LPG (liquefied petroleum gas), CNG (Liquefied natural gas).
  • They are used in the manufacturing of polymers such as polyethylene, polystyrene etc.
  • These organic compounds find their application in the manufacturing of drugs and dyes as a starting material.
  • They serve as lubricating oil and grease.

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Practise This Question

Which of the following gives CH4 on hydrolysis?