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Homework Help: Preferential meta para and ortho positions substitutions.

  1. May 17, 2008 #1
    1. The problem statement, all variables and given/known data

    If i have 4 methyl phenyl amine and i add aqueous bromine. where will the bromine atom substitute.

    And would adding aqueous bromine to 3 methyl phenol have a different reaction/observation.

    2. Relevant equations

    3. The attempt at a solution

    I think it will depend on which is a stronger activating group. the methyl or amine group.

    both organic compounds react similarly with bromine, with the same observations.
    Discharge of reddish brown colour + acidic fumes of HBr.

    the reaction is electrophilic substitution in both.
    Last edited: May 17, 2008
  2. jcsd
  3. May 17, 2008 #2
    Exactly. There are two competing activating groups; therefore the addition will most likely occur at the position that is favored by the most activating group. So which one is stronger? What kind of director is it?
  4. May 17, 2008 #3
    both methyl and amine groups are ortho and para directing because they are activating groups.

    but i don't know which one is stronger.
  5. May 17, 2008 #4
    this is something you could find pretty easily in your orgo text, but resonance donation typically has a stronger directing effect than hyperconjugation.
  6. May 18, 2008 #5
    what you saying is advanced chemistry for me!! we don't do resonance.

    but can you tell me which groups are stronger and which are weaker?!

  7. May 18, 2008 #6
    You are asking a question from a second semester organic chemistry course. It's silly to even think about this question if you haven't already covered the prerequisite concepts to understand it. In order to understand a substituents directing effects you absolutely need to think about resonance, otherwise you are just blindly memorizing.

    What year are you in school?
  8. May 18, 2008 #7
    i'm in last year of high school. we do cambridge A levels. sometimes they give organic questions with different activating groups attached to a benzene ring and where a slight knowledge of which activating/deactivating group is stronger and weaker might be very helpful, at least to understand the problem.

    we also study many reactions without getting into the mechanisms: elimination rxns,...
  9. May 19, 2008 #8
    It's quite strange that they would teach you like that without covering the concepts that make it understandable... anyway, you can easily find in a textbook, or on the internet, which group is a stronger activator.
  10. May 19, 2008 #9
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