Dehydrogenation of Alkanes & Alkenes

[Syed Ammar]

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

 

[Adithyan]

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.

 

[Syed Ammar]

Plz provide the reaction with complete conditions...

 

[Adithyan]

Find out more about elimination reactions yourself and then try to apply the logic to other reactions. You can start from the following links:

http://en.wikipedia.org/wiki/Elimination_reaction

https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/react1.htm#rx4

https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/react3.htm#rx10

Best of luck!