Why Doesn't the Epoxide React?

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Discussion Overview

The discussion revolves around the reactivity of an epoxide in a chemical reaction, specifically exploring why the epoxide does not react as expected. Participants examine mechanisms such as nucleophilic substitution and the stability of the epoxide ring, with a focus on theoretical aspects of organic chemistry.

Discussion Character

  • Homework-related
  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant suggests that C2H5O- can attack the epoxide ring via an SN2 mechanism, potentially at the less substituted carbon or at the carbon attached to oxygen.
  • Another participant asserts that the epoxide ring is reacting and questions the placement of the epoxide on the C-14 atom in the context of the answer provided.
  • A different participant expresses confusion about why nucleophilic substitution does not occur at the carbon attached to Cl, proposing that the major product should be the one that is easier to form and more stable.
  • Concerns are raised about the stability of the sp3 carbon with a bond angle of 60°, suggesting that breaking the epoxide ring would lead to a more stable product.
  • One participant clarifies that while the epoxide may be less stable due to angle strain, it does not imply that it is unstable overall.
  • There is a discussion about the role of alkoxide as a strong nucleophile and Cl as an excellent leaving group in the formation of the epoxide in a later step.

Areas of Agreement / Disagreement

Participants express differing views on the reactivity of the epoxide and the mechanisms involved. There is no consensus on the reasons for the epoxide's lack of reactivity or the stability of the products formed.

Contextual Notes

Participants reference specific steps in the reaction mechanism and the stability of intermediates, but there are unresolved assumptions regarding the conditions under which these reactions occur and the definitions of stability being used.

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Homework Statement


https://www.box.com/s/qs19ng6qvcget7g69ad3

Homework Equations


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:
 
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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:
AGNuke said:
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

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?
 
Pranav-Arora said:
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?
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:
AGNuke said:
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.

If it's not stable as you say, then why the epoxide ring is formed in the product?
 
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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