Hydrocarbons

A hydrocarbon refers to an organic compound comprising entirely hydrogen and carbon. These types of compounds are generally colourless, hydrophobic and also with weak odours. Majority  anthropogenic hydrocarbons are emitted from burning of fossil fuels involving fuel production and combustion. Some of the natural sources of hydrocarbons like ethylene, monoterpenes, and isoprenes is by the emission of vegetation. Mainly hydrocarbons are the constituents of petroleum and natural gas.

Majority of hydrocarbons occur in nature. Along with the making of fossil fuels these compounds are also present in trees and plants as seen in carotenes pigment found in carrots and green leaves. A chain-like molecule containing many units that are linked together refers to a polymer, greater than 98% of natural crude rubber represents a hydrocarbon polymer. The structure of all the individual hydrocarbons depends on the types of chemical bonds that link together the atoms of the constituent molecule. 

Classification of Hydrocarbons

The four different types of hydrocarbons are discussed below:

Alkanes 

These are the most simplest form of hydrocarbons having only single bonds of two elements. Alkanes are referred to as true hydrocarbons since there are no other elements contained in it. They can be represented by a molecular formula of CnH2n+2 , where n refers to the number of carbon atoms. Very common three forms of alkanes can be named as methane (CH4), ethane (C2H6) and propane (C3H8). Not only alkanes are a good source of fuels like many other hydrocarbons, but also they are harmful for the environment when combusted. Methane, an alkane, is a gas which causes global warming.

Alkenes

Similar to alkanes, alkenes are also true hydrocarbons with no other element in their composition. According to the name alkenes consists of at least one carbon-carbon double bond.  They are represented as CnH2n . Very common and less complex alkenes are ethene (C2H4) and propene (C3H6). The main difference between an alkane and an alkene is the presence of a double bond. 

Alkynes

This type of hydrocarbon contains only hydrogen and carbon atoms. These are also true hydrocarbons, alkynes differ from alkanes and alkenes by the presence of a triple bond between two carbon atoms. The molecular formula of alkynes can be written as CnH2n-2 . The common varieties of an alkyne can be like – ethylene (C2H2), propyne (C3H4) and butyene (C4H6). 

Aromatic hydrocarbons

These types also contain only hydrogen and carbon. Aromatic hydrocarbons are more complicated than many other types of hydrocarbons. These are referred to as aromatic hydrocarbons due to the presence of a characteristic smell. The least complicated and most common type of hydrocarbon is benzene (C6H6). Benzene can be found in fuel sources like petroleum, diesel and kerosene.

Properties of Hydrocarbons

Physical properties: the physical properties of alkenes and alkynes are similar to those of alkanes or cycloalkanes having the same number of carbon atoms. Alkynes possesses a higher boiling and melting points than alkenes and alkanes as the electric field of an alkyne along with its weakly held π electrons are more easily distorted, leading to a stronger attractive forces between molecules. The force of attraction is stronger in alkynes than alkenes and alkanes.

Chemical properties: Alkenes can react with a more variety of compounds than alkanes. Alkanes undergo substitution whereas alkenes and alkynes undergo addition reactions. 

Reactions

Hydrocarbons undergoes mainly three types of reactions such as:-

• Substitution reaction: these reactions are undergone by aromatic hydrocarbons as seen on reaction of benzene with ethylene to form ethylbenzene.

• Addition reaction: different types of alkenes and alkynes are destined to undergo these reactions in which various types of reagents are added across the π bonds these reagents are like HCl, Hydrogen and Chlorine. 

• Combustion reaction: hydrocarbons upon combustion produces heat and electrical energy which can be used as home heaters which uses petroleum and natural gas. 

Sources of Hydrocarbons

The vital source of hydrocarbons are fossil fuels such as coal, petroleum, and natural gas. Fossil fuels are formed over hundreds of years, when dead organic remains of animals were covered with sediments and were kept under great pressure. Giant ferns found in ancient swamps have turned into coal deposits. Dead organic remains in ancient seas are slowly forming deposits of petroleum and natural gas. 

 Uses of Hydrocarbons

• Most common use of hydrocarbons is as fuels like LPG (liquefied petroleum gas) and CNG (compressed natural gas).

• Hydrocarbons are used in the manufacturing of various types of polymers like polythene and polystyrene. 

• These compounds can also be used in the manufacture of drugs and dyes.

• Hydrocarbons act as a lubricating oil or grease.

• Hydrocarbon usage is also well known in nature, as seen in Brazilian stingless bee which uses cuticular hydrocarbons i.e. “scents” in order to determine kin from non-kin.

• Many different industries use aliphatic hydrocarbons such as gasoline, naptha and jet fuels.

Conclusion

Hydrocarbons are differentiated on the basis of their physical and chemical properties. Based on their solubility hydrocarbons are insoluble and immiscible in water since they are polar substances with respect to high polarity of water. The densities of different types of hydrocarbons are found to be the same except for an exception chlorobenzene, this is due to the presence of hydrogen bonds that need to be broken. Aromatic compounds are generally unreactive as they are stable compounds, and only react in the presence of a catalyst. We hope with the help of this article you were able to clear all your doubts regarding hydrocarbons, its structure, properties, reactivity, sources, uses and its examples.