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Halogenation Of Alkenes Tutorial Video

October 17, 2012 By Leah4sci 18 Comments

alkene bromination mechanismAlkene Reactions Series: Video 3
Halogenation of alkenes is the reaction in which a double bond is broken and replaced by a vicinal dihalide – 2 halogen atoms added to neighboring carbons. This reaction follows a pattern of anti addition.

The goal of this video is to help you understand rather than memorize concepts related to the halogenation mechanism. This video addresses dihalide polarization, bromonium/chloronium bridge formation, addition to cyclic and asymmetrical starting alkenes.

(Watch on YouTube: Halogenation. Click cc on the bottom right for video transcription.)

<– Watch Previous Video: Hydrohalogenation of Alkenes
–> Watch Next Video: Halohydrin formation

This is Video 3 in the Alkene Reaction Mechanisms Video Series. Click HERE for the entire series.

Ready to test your skills? Try the Alkene Reactions Practice Quiz after watching the series!

Filed Under: Organic Chemistry Tutorial Videos Tagged With: alkene reaction mechanism, alkene reactions, halogenation, halogenation of alkenes

Comments

  1. Krystal T says

    January 28, 2018 at 2:33 pm

    Why does the bromine attack back with its elections? I don’t see what the driving force for that would be.

    Once the pi bond attacks the bromine, doesn’t that make a bond?

    Reply
  2. Basil Mohamd says

    November 1, 2017 at 11:27 pm

    Hi, i would like to know why the chlorine was not on wedges or dashes in the last example.

    Reply
  3. Megan says

    October 13, 2017 at 6:03 pm

    Why does chlorine not form a bridge like bromine?

    Reply
  4. Mike says

    October 31, 2016 at 12:30 am

    Hi Leah, since the bromine in the bridge has a positive formal charge and the other bromine is negative. Why is the negative bromine attracted to the partially positive carbon instead of the other positive bromine?

    Thanks

    Reply
  5. Diamonn says

    July 11, 2016 at 10:43 pm

    Do you have any videos on Radical Rxns, NBS, Allylic carbon, how to calculate delta H for propagation steps? That is what I am doing now in my Orgo II class.

    Reply
    • Leah4sci says

      August 12, 2016 at 10:38 am

      I cover some of these topics in the Organic Chemistry Study Hall. Join here: https://leah4sci.com/join

      Reply
  6. munyaradzi chiunye says

    June 30, 2016 at 6:55 am

    Hi Leah, I think you are doing a fantastic job. I think you can add a DONATE button so that people can donate to you. It is another way people can say thank you!!

    Reply
    • Leah4sci says

      July 3, 2016 at 10:58 am

      Thanks for the suggestion Munyaradzi! The best way to donate is
      1- sign up for my services or study hall
      2- tell your friends about my free resources and perhaps they will sign up

      Reply
  7. Brian says

    March 8, 2016 at 5:05 am

    In the last example, propene reacting with Cl2, do we still worry about stereochemistry?

    Reply
    • Leah4sci says

      April 4, 2016 at 5:41 pm

      Only for the central carbon which WILL be chiral but racemic

      Reply
  8. Francis B. Banks (Ph. D., MRSC) says

    February 22, 2015 at 4:36 pm

    Hi all. The description of resonance in the bromonium ion intermediate is rather misleading. The contributing structures have no independent existence. There is no “back and forth” between them. The actual structure is a sort of average of them, and always contains two bonds to the bromine atom.

    Reply
    • Leah4sci says

      May 4, 2015 at 2:27 pm

      You are correct. The video is taught to help understand the partial positive charge (unless I made a mistake which sometimes happens)

      Reply
  9. Ashley says

    November 30, 2012 at 2:08 pm

    Hi Leah, I’m confused as to why the bromine in the bromine bridge has a positive charge, when it has three lone pairs, and two bonding electrons. Shouldn’t it have a negative charge? Or maybe should have only two lone pairs?

    Reply
    • Francis B. Banks (Ph. D., MRSC) says

      February 22, 2015 at 4:33 pm

      Actually the bromine in the bridge has two lone pairs and two bonding pairs. Since bromine is in group 7, the calculation is 7 – 2×2 -2×1 = +1.

      Reply
      • Leah4sci says

        February 25, 2015 at 11:29 pm

        Yup that was an error I caught after posting. YouTube doesn’t let me correct live videos and I won’t delete it just for that

        Reply
      • Idan b says

        April 23, 2016 at 3:28 pm

        hello, so if the bromine in the bridge has two lone pairs and two bonding pairs, where are the pair electrons we started with gone to??

        thank you very much for those videos !

        Reply
        • Leah4sci says

          May 3, 2016 at 8:55 am

          Idan: The bonding pair is the former lone pair

          Reply

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