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More alkyl groups you're attached to means you are more energetically

  1. Jul 8, 2012 #1
    In alkenes, the more alkyl groups you're attached to means you are more energetically stable, and that we know the reactivity increases as the stability of the intermediate carbocation increases (with tertiary the most stable)

    I'm puzzled by this relationship, how is it that when it is more stable, the reactivity increases.

    I suspect that it is because when a primary carbocation is less stable, it tends to revert back to its previous form, thus deterring the reaction while a tertiery carbocation is more readily formed and react with other substances.

    I would appreciate it deeply if anyone who can clear my doubts :)

    EDIT: There was a mention that the stability of the intermediate ions governs the activation energy for the reaction. (It would be nice to explain this line too!)
     
    Last edited: Jul 8, 2012
  2. jcsd
  3. Jul 10, 2012 #2

    DrDu

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    Re: Carbocation

    Maybe you can formulate your question more clearly. First you mention stability of alkenes, then you talk of carbocations and then you are taking about some unspecified reaction.
    For some basic chemical kinetics, this article in wikipedia may be a starting point:
    http://en.wikipedia.org/wiki/Transition_state_theory
     
  4. Jul 10, 2012 #3
    Re: Carbocation

    I'm sorry for the poorly-phrased question, give me another try at this.

    An intermediate ion with tertiary carbocation is the most stable right? This is because it has the most alkyl group attached to it, thus making it stable.

    There is also a mention that the more stable the intermediate ion(that is the tertiary carbocation in this case) is, the better the reactivity(means the faster it reacts). I'm confused how is it that a more stable compound can be more reactive.

    Also there is a line that says that the intermediate ion governs activation energy, I feel that this line may help me understand my question better, however I fail to see any significant relationship between the activation energy and the intermediate ion.

    I hope this is better.
     
  5. Jul 10, 2012 #4

    DrDu

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    Re: Carbocation

    I asked you to specify the reaction you have in mind. I suppose you are taking about some reaction of an alkene with an electrophilic.


    Yes
    The point is not that the carbocation reacts more rapidly but that it is formed more rapidly which is the step which limits the velocity of the reaction.
     
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