Organic Chemistry/Introduction to reactions/Hydrohalogenation

From Wikibooks, open books for an open world
< Organic Chemistry‎ | Introduction to reactions
Jump to: navigation, search
A simple alkene undergoing hydrohalogenation
A simple alkene undergoing hydrohalogenation

Alkenes are electron-rich. Just look at those electrons all clumped together in the carbon-carbon double bond. They act as Lewis bases (they give up electrons).

Hydrohalogenation follows Markovnikov's rule. That is, the carbon of the double bond that starts out more subsituted recieves the halogen (becomes more substituted) while the carbon of the double bond that starts out less substituted ends up with the hydrogen.

A substituated alkene undergoing hydrohalogenation
He who has, gets: This is another alkene illustrating hydrohalogenation. Notice how the more highly substituated carbon ends up with the X-


The H+ is attracted to the electron-rich double bond and adds first, on the carbon with more hydrogens, leaving the other carbon with a positive charge (a carbocation). Then the X- reacts with the carbocation.


Read about Vladimir Vasilevich Markovnikov on Wikipedia.