Dehydrogenation of Alkanes & Alkenes

  • Thread starter Syed Ammar
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In summary, the conversation discusses the process of converting alkanes and alkynes into alkenes through hydrogenation and the reverse process of preparing alkenes from alkanes and alkynes from alkenes. The use of chromium (III) oxide as a catalyst at 500 °C is mentioned as a valid method for dehydrogenation of alkenes, with examples of n-pentane and isopentane being converted to pentene and isopentene. It is also suggested that elimination reactions can be used to obtain unsaturated hydrocarbons from haloalkanes, with additional resources provided to learn more about these reactions.
  • #1
Syed Ammar
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By hydrogenation, alkynes form alkenes and alkenes form alkanes but I need the reverse process i.e preparation of alkenes from alkanes and alkynes from alkenes...
I have found a reaction for dehydrogenation of alkenes at Wikipedia but I am not sure if it works for all alkenes: QUOTE
"n-pentane and isopentane can be converted to pentene and isopentene using chromium (III) oxide as a catalyst at 500 °C."

Ref:http://en.wikipedia.org/wiki/Dehydrogenation
 
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  • #2
Yes Chromium oxide reaction is valid for all alkanes. In fact, many metal (III) oxides are capable of producing such reactions on specific compounds. Examples are Aluminum and Iron (III) oxide.

If it isn't compulsory to use a one step process, you can use elimination reaction to obtain unsaturated hydrocarbons from haloalkanes.
 
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  • #3
Plz provide the reaction with complete conditions...
 
  • #5


Thank you for your question. I can provide you with information about the dehydrogenation of alkanes and alkenes and the reverse process of preparing alkenes from alkanes and alkynes from alkenes.

Dehydrogenation is a chemical reaction in which hydrogen atoms are removed from a molecule, resulting in the formation of a double or triple bond. This process can be used to convert alkanes to alkenes and alkynes.

One method of preparing alkenes from alkanes is through the use of a catalyst, such as chromium (III) oxide, at high temperatures (around 500 °C). This process is known as thermal dehydrogenation and is commonly used in industrial settings to produce large quantities of alkenes.

Another method is through the use of a chemical reaction known as dehydrohalogenation. This involves the removal of a hydrogen atom and a halogen atom (such as chlorine or bromine) from a molecule, resulting in the formation of an alkene. This process is often used in organic chemistry laboratories to prepare specific alkenes.

To prepare alkynes from alkenes, a process called oxidative dehydrogenation can be used. This involves the use of an oxidizing agent, such as potassium permanganate, to remove two hydrogen atoms from an alkene, resulting in the formation of an alkyne.

It is important to note that the specific conditions and catalysts used for dehydrogenation reactions may vary depending on the starting material and desired product. Therefore, it is important to carefully research and select the appropriate method for the specific reaction you are trying to perform.

In conclusion, while the reaction you found on Wikipedia may work for the specific alkanes and alkenes mentioned, it may not be applicable for all alkenes. It is important to carefully consider the conditions and catalysts needed for each specific reaction in order to achieve the desired product.
 

1. What is dehydrogenation of alkanes and alkenes?

Dehydrogenation is a chemical process in which hydrogen atoms are removed from molecules, specifically alkanes and alkenes. This process is often used to produce unsaturated hydrocarbons, such as alkenes, which can be used to make plastics, rubber, and other products.

2. How is dehydrogenation of alkanes and alkenes carried out?

Dehydrogenation is typically carried out using a catalyst, such as platinum or palladium, at high temperatures and pressures. This allows for the removal of hydrogen atoms from the alkane or alkene molecule, resulting in the formation of a double bond.

3. What are the benefits of dehydrogenation of alkanes and alkenes?

Dehydrogenation is an important process in the production of various industrial materials, including plastics, rubber, and fuels. It also allows for the conversion of alkanes, which are less reactive, into alkenes, which are more reactive and can be used to create a wider range of products.

4. What are the potential drawbacks of dehydrogenation of alkanes and alkenes?

One potential drawback of dehydrogenation is the high energy and resource requirements. The process often requires high temperatures and pressures, as well as the use of expensive catalysts. Additionally, this process can also produce unwanted byproducts, which can be harmful to the environment.

5. Can dehydrogenation be used to produce renewable energy?

Yes, dehydrogenation can be used to produce renewable energy. By using biomass as a source of alkanes and alkenes, the dehydrogenation process can produce biofuels, such as ethanol, which can be used as a renewable energy source. This process is more sustainable and can help reduce our reliance on fossil fuels.

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