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Epoxide does not react?

  1. Sep 4, 2012 #1
    1. The problem statement, all variables and given/known data
    https://www.box.com/s/qs19ng6qvcget7g69ad3 [Broken]


    2. Relevant equations



    3. The attempt at a solution
    I think that there are two possibilities. First, C2H5O- can attack at the epoxide ring by the SN2 mechanism (i guess the attack will take place at the less substituted carbon in the epoxide ring) and the second is that nucleophilic substitution can place at the carbon attached to oxygen by the SN2 mechanism.
    But which of the two possibilities would happen and why? I am stuck here.

    The answer given is D but why does the epoxide ring does not react?

    Any help is appreciated. :smile:
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 5, 2012 #2

    AGNuke

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    Epoxide ring is reacting. See, in the question, Epoxide was on C-14 atom, but in the answer you mentioned, Epoxide is not on C-14 atom.

    Here's my take.

    C1%2520-%2520Copy.png
     
    Last edited: Sep 5, 2012
  4. Sep 5, 2012 #3
    I too was thinking that the neighbouring group mechanism would follow but why doesn't nucleophilic subsitution take place at the carbon attached to Cl?
     
  5. Sep 5, 2012 #4

    AGNuke

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    If you are talking for the first step, my guess would be that the major product formed will be from the reaction which is easier to proceed and the result is more stable.

    In the case of epoxide, you can see that sp3 carbon with bond angle 60° is not the best idea for stability. So, the major product should involve in breaking this epoxide ring, so it happens in Step 1.

    It is another story that Intramolecular SN2 happens in Step 2. Basic Environment causes the formation of Alkoxide ion, which is highly reactive and a strong Nucleophile. So, it forms epoxide at the cost of Cl atom leaving. Intramolecular SN2 Substitution
     
    Last edited: Sep 5, 2012
  6. Sep 6, 2012 #5
    If it's not stable as you say, then why the epoxide ring is formed in the product?
     
  7. Sep 6, 2012 #6

    AGNuke

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    Read the next line. Alkoxide is a strong nucleophile, and Cl is an excellent leaving group, so it will just leave and epoxide will form. This is step 2, different story altogether.

    Who said that "less" stable products can't be formed. And I didn't said epoxide not stable. Only "Less" stable, owing to the account the angle strain of sp3 bonds.
     
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