Difference Between Alkanes and Alkenes

May 22, 2023 · 5 min read ·

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Main Difference

The main difference between Alkanes and Alkenes is that the Alkanes are the hydrocarbons in which the main chain of a carbon atom contains a single bond, whereas the Alkenes are the hydrocarbons in which the main carbon chain contain a double bond.

Alkanes vs. Alkenes

Alkanes are the saturated hydrocarbons, whereas the alkenes are the unsaturated hydrocarbons. Alkanes are the hydrocarbons of containing a single bond in the main chain, whereas the alkenes are the hydrocarbons of containing multiple bonds of a double bond. The general formula of alkanes is CnH2n+2, whereas the general formula of alkenes is CnH2n.

The process of polymerization is not common in alkanes, while the process of polymerization is very common in alkenes. Alkanes contain only sigma bond and no pi bond on the flip side, alkenes contain both sigma and pi bond in the carbon chain. Alkanes experience reactions of substitution, whereas alkenes experience reactions of addition. Alkanes do not undergo electrophilic addition reactions; on the other hand, alkenes can undergo electrophilic addition.

Alkanes undergo free radical mechanisms, while such reaction is not common in alkenes. Alkanes do not change the brown color of bromine water, whereas the alkenes can change the brown color of bromine water into colorless. Alkanes do not show the reaction with alkaline or acidic KMnO4, whereas the alkenes show reaction with alkaline or acidic KMnO4 and change the purple color of the solution.

Alkanes are considered as less reactive towards the agents of electrophile; on the other hand, the alkenes are considered as more reactive toward the electrophilic agents. Alkanes are less reactive as there are fewer chances of availability of electrons; on the flip side, alkenes are more reactive as there are more chances of the availability of free electrons.

Alkanes can show reactions only in the presence of sunlight, whereas the alkenes can show reactions both in the existence or deficiency of sunlight. An example of alkanes is ethane, whereas the example of alkenes is ethene.

Comparison Chart

Alkanes	Alkenes
The alkanes are the hydrocarbons in which the main chain of a carbon atom contains a single bond.	The alkenes are the hydrocarbons in which the main carbon chain contains a double bond.
Hydrocarbons
Saturated	Unsaturated
General Formula
CnH2n+2	CnH2n
Numbers of Bonds
Single bond	Double bond
Reactivity
Less reactive	More reactive
Types of Bonds
Only sigma bond	Sigma and pi bond
Reactions
It can show a substitution reaction	It can show addition reaction
Sunlight
Only in the presence of sunlight	Absence or presence of sunlight
Example
Ethane	Ethene

What are Alkanes?

The saturated hydrocarbons contain only a single bond in the main carbon linkage. Alkanes contain only a sigma bond and pi bond is absent in alkanes. That’s why it decreases the chances of availability of electrons in the compound. Due to this reason, alkanes are considered as less reactive towards the agents of the electrophile.

It cannot show the addition reaction in the biochemistry. It can only give substitution reactions and free radical mechanisms. It is also utilized in the production of many different organic compounds of chemistry. But it can only give such type of reactions in the presence of sunlight or UV lights or the presence of catalysts.

It cannot give reactions to the bromine water solution in the presence of CCl4 and cannot change its reddish-brown color of the solution. It does not have any tests of its identification. Alkanes also do not form precipitation in the ammonical water solution. Examples of alkanes are Methane, ethane, propane, butane, pentane, etc. are included in the examples of alkanes.

What are Alkenes?

The unsaturated hydrocarbons contain multiple bonds, such as the triple bond in the main carbon linkage. Alkenes contain both sigma and pi bonds in the compound. It increases the chances of the availability of electrons in the compounds. Due to these reasons, alkenes are more reactive towards the electrophilic reagents than the alkanes and alkynes.

It can show additional reactions in the labs of chemistry. It can also give other reactions such as dehydration, polymerization processes, etc. it can give these reactions in the presence or absence of light or the presence of catalysts, can give better reactions.

It can show reaction with bromine water and can change the color of bromine reddish-brown into colorless. It also does give reactions to an ammonical water solution. Examples of alkenes are ethene, propene, butene, etc. are included in the examples of alkenes.

Key Differences

Alkanes are included in the category of the saturated hydrocarbons, whereas the alkenes are included in the category of the unsaturated hydrocarbons.

Alkanes are the saturated hydrocarbons that consist of a single bond in the main carbon chain, whereas the alkenes are the unsaturated hydrocarbons that consist of multiple bonds of the double bond in the main carbon chain.

The general formula of alkanes is CnH2n+2, whereas the general formula of alkenes is CnH2n.

The polymerization process does not occur in hydrocarbons of alkanes, while the polymerization process usually occurs in the hydrocarbons of alkenes.

Only a sigma bond is present in the carbon chain of alkanes; on the flip side, both sigma and pi bond is present in the carbon chain of alkenes.

Alkanes face the substitution reaction, whereas alkenes go through the addition reaction.

Alkanes do not go through electrophilic addition reactions; on the other hand, alkenes can go through the electrophilic addition.

Free radical mechanisms occur in alkanes, while the free radical mechanism does not occur in alkenes.

Alkanes do not alter the brown color of bromine water, whereas the alkenes can alter the color of bromine water from brown to colorless.

The reaction with alkaline or acidic KMnO4 is not common in alkanes, whereas the alkenes show reaction with alkaline or acidic KMnO4 and variate the purple color of the solution.

Alkanes are believed as less reactive in the presence of the agents of electrophile; on the flip side, alkenes are believed as more reactive in the presence of the agents of the electrophile.

Alkanes are less reactive in the chemical reactions; on the other hand, alkenes are more reactive in the chemical reactions.

The reactions of alkanes occur only in the presence of sufficient sunlight, whereas the reactions of alkenes occur both in the absence and presence of sunlight.

Conclusion

The above discussion concludes that both alkanes and alkenes are types of hydrocarbons. Alkanes are the hydrocarbons containing only a single sigma bond in the main carbon chain, whereas the alkenes are the hydrocarbons containing both sigma and pi bond in the main carbon chain.

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