What is Olefin?

Olefin is a very common term used in organometallic compound chemistry. Let’s discuss the olefins meaning, olefins are generally called alkenes. These are the family of hydrocarbons that contain double bonds. Hydrocarbons are the compound made up of hydrogen and carbon. Alkenes or olefins are unsaturated hydrocarbons


Olefins Examples

The common olefins examples are propane, ethene, butene, and pentene. In the IUPAC naming system, the name of the olefins suffixes with the “ene”. Olefins are unstable compounds. The reactivity of the paraffin is lower than the olefins. Olefins due to low solubility react with various compounds.


What is an Olefinic Bond?

The olefinic bond is the type of bond present in the unsaturated hydrocarbon. These are unsaturated bonds or pi bonds (double bonds) present in the hydrocarbon. It is represented as >C=C<. The presence of an olefinic bond in the alkenes makes the compound insusceptible for movement or rotation. Therefore, these compounds do not show conformer isomers. These compounds do not undergo a substitution reaction.


Name and Formulae of Alkenes

Formula (CnH2n)

Name 

C2H4

Ethene 

C3H6

Propene 

C4H8

Butene 

C5H10

Pentene 

C6H12

Hexene 

C7H14

Heptene 

C8H16

Octene 


Olefin Structure

Few Examples Showing Olefin Structure Are Given Below

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The above-shown compounds are olefin compounds as they all have double bonds. The general olefin chemical structure is represented as >C=C< (Carbon-carbon double bond). The unsaturated carbons in the olefins are sp2 hybridised. 


Types of Olefins

  1. Aliphatic olefins

  2. Aromatic olefins

  3. Cyclic olefins

Aliphatic Olefins - These are the compounds that do not participate in the resonance. It can be further divided into two parts: cyclic olefins and acyclic olefins. When these olefins exist in cyclic form these are called cyclic form and when they exist in an open-chain form these are called acyclic olefins.

Aromatic Olefins - these are the unsaturated compounds that exist in the ring form and the double bonds in them are arranged in an alternate manner. Due to such an arrangement, these compounds show resonance. The aromatic olefins are more stable than the aliphatic hydrocarbon due to the resonance energy. Aromatic olefins follow huckel's rule.

Monolefins and Diolefins - Monolefins contain single double bonds and diolefins contain two double bonds. Diolefins are more unsaturated than monolefins. 


Properties of Olefins

Physical Properties of Olefins

  • These compounds exist in solid, liquid, and gases form. The lower alkenes (ethene, propene, and butene) exist in the gas state, the next fourteen-member exist in the liquid phase, and the higher number of carbon olefins exist in the solid-state.

  • Olefins are colourless compounds.

  • Olefins are odourless compounds, except ethene.

  • Olefins are generally insoluble in polar compounds like water.

  • Olefins are soluble in non-polar solvents like benzene.

  • The boiling point of the olefins depends on the number of a carbon atom. It increases with the increase in the number of a carbon atom. The boiling point of the olefins is inversely proportional to the surface area of the compound. Therefore, the boiling point of the branched olefins is lower than that of straight-chain olefin compounds.

  • The melting point of the olefins depends on the position of the double bond. The melting point of the cis olefin isomer is lower than that of the trans olefin isomer.

  • These are the non-polar compounds.


Chemical Properties of the Olefins

Alkenes undergo an additional reaction. 

  1. Hydrogenation Reaction - Alkenes (olefins) undergoes a hydrogenation reaction in the presence of palladium or platinum.

  2. Halogenation Reaction - Alkenes gives a halogenation reaction in the presence of bromine or chlorine.

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  1. Hydration Reaction - alkenes undergo a hydration reaction in the presence of water and form alcohol.

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  1. Alkenes or olefins undergo combustion reaction.

  2. Olefins decolourise the bromine water.

  3. Olefins have the ability to undergo polymerisation reactions.

  4. Olefins give Markovnikov reactions and anti-Markovnikov reactions.


Olefin Chemical Formula

The olefins are generally known as alkenes. The olefin formula is CnH2n.  The carbon at the double bond position is sp2 hybridised. The double bond present in the olefins acts as a functional group.


Did You Know?

  • Olefins can be prepared by the cracking of alkanes.

  • Dehydration of alcohols leads to the formation of alkenes.

  • The pi bonds present in the olefins are loosely held together.

  • The most common reaction given by olefins is an ozonolysis reaction. It is a type of oxidation reaction in the presence of ozone and water. Aldehydes, ketones, and acids are formed as a product in this reaction.

FAQs (Frequently Asked Questions)

1. Name some reagents with which the olefins give a reaction.

Olefins can react with bromine or chlorine, potassium manganate, hydrogen, hydrogen halide, and steam.

2. Why are there no olefins that can be formed with only one carbon atom?

Olefins are the unsaturated compound, which means they contain carbon-carbon double bonds. So for the formation of a double bond we need at least two carbons. Therefore, no single carbon olefins exist.