Dhristi JEE 2022-24

An Introduction

Science is a spectacular subject that studies the universe from different angles by applying a methodology of experimentation and trials and error. This makes it believable and reasonable for students to understand the concept and process behind anything that happens in our surroundings, be it natural occurrences like rain and thunder or artificial processes like Electricity and energy production etc. This is mainly divided into three categories for the students namely- Physics, Chemistry and Biology. This article deals with the topic of chemistry.


Chemistry is the study of substances and their chemical properties, reactions and natural occurrences. Chemistry helps students understand the several natural and man-made processes and changes in the environment. In this article, Students can learn about all the necessary details and concepts of Olefin.


Olefin is a very common term used in organometallic compound chemistry. Let’s discuss the meaning, olefins are generally called alkenes. These are the family of hydrocarbons that contain double bonds. Hydrocarbons are compounds 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

Propane 

C4H8

Butane 

C5H10

Pentane 

C6H12

Hexene 

C7H14

Heptane 

C8H16

Octane 

 

Olefin Structure

Few Examples Showing Olefin Structure Are Given Below

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 forms 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.

 

Mono Olefins 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 gas 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 carbon atoms. It increases with the increase in the number of carbon atoms. 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.

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

  1. Alkenes or olefins undergo combustion reactions.

  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 alcohol 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.

 

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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 unsaturated compounds, 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.

3. How long will it take for the students to complete the reading and understanding of the concept of Olefin from the above article of Vedantu?

Students of chemistry will get a basic understanding on the concept of Olefin from the above article in approximately 40 to 45 minutes of continuous reading with attention. As a result, students will get the quintessential of all the necessary details of this topic.

4. What are some quick tips for the students to revise for the science exam? 

Vedantu provides a variety of Revisions and keynotes of all subjects and all classes for the students of CBSE, ICSE and State boards as well. Vedantu also provides several Previous Year's question papers and sample question papers solved by the team of expert and skilled teachers at Vedantu. Students can also improvise their revision by reading important questions on all topics at Vedantu to get a better command and for foolproof preparation in exams.

5. Why should students prepare for exams only from Vedantu?

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6. Which classes include the topic of Olefin in the syllabus of chemistry for students? 

Students of Class 9, 10, 11 and 12 will find Olefin as an important part of their syllabus. As a result, students are required to have a strong foundation of this topic of chemistry right from the beginning. Apart from the above article, students can also learn about Olefin from the free study material provided by Vedantu and also other Micro courses available on the platform.

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