[laze]

I am told to predict the major substitued product for a Williamson Ether Synthesis involving 1-methoxy-2-chloro-cyclohexane and sodium methoxide and to rationalize it.

I said that since the chlorine is attached to a 2ndary carbon it is a 2ndary haloalkane, and that with secondary/tertiary haloalkanes in a williamson ether synthesis it tends to be elimination rather than an SN2 reaction. I said it undergoes dehydrohalogenation and forms the product 1-methoxy-cyclohex-1-ene, which is incorrect.

I was then hinted to think about involvement of anchimeric assistance
in the formation of the major observed product.

Well im looking up what that exactly means and im also having a hard time seeing how to work it into this problem.

Thanks in advance for any help.

[discodermolide]

It may or may not help but "involving 1-methoxy-2-chloro-cyclohexane " is actually 1-chloro-2-methoxycyclohexane.
Think about involving the methoxy group somehow in the elimination process.

[laze]

Would the lone pairs on the oxygen contribute somehow to the elimination process?

[discodermolide]

I think they may help. Try it out and see what you get.

[orgopete]

Is this problem correct? I don't understand how this would be classified as a Williamson ether synthesis. I am not following this reaction either. What is the purpose of the NaOMe? This would make more sense (as a reaction) if it were the chloro alcohol that is being treated with NaOCH3. That could give a methoxy alcohol.

[laze]

Thats why I am confused.

"Contemplate the Williamson ether reaction involving
1‐methoxy‐2‐chlorocyclohexane and sodium methoxide. Rationalize the
formation of the major observed substitution product."

Is the exact wording of the problem. When i told my prof what i thought it was, he said to consider the involvement of anchimeric assistance
in the formation of the major observed product.  I really don't know how to proceed. He said that it was a tricky problem.

[discodermolide]

You suggested trying to involve the oxygen lone pairs, did you try this?

[orgopete]

You suggested trying to involve the oxygen lone pairs, did you try this?

Why is NaOMe present? I don't see how you are going to do a substitution reaction with it. I agree with the poster, a secondary halide will result in an elimination reaction. If it is a solvolysis reaction in methanol, then why use NaOMe?

[discodermolide]

You suggested trying to involve the oxygen lone pairs, did you try this?

Why is NaOMe present? I don't see how you are going to do a substitution reaction with it. I agree with the poster, a secondary halide will result in an elimination reaction. If it is a solvolysis reaction in methanol, then why use NaOMe?

I don't know why NaOMe is present, perhaps it came with the question from the book or whatever he is using.

[laze]

You suggested trying to involve the oxygen lone pairs, did you try this?

I don't know what to do with the lone pairs on the oxygen in the methoxy group on the cyclohexane.  I don't know how to apply
anchimeric assistance with that oxygen to the overall reaction.  At first i thought it would be an ether that was formed, then i read up on william ether synthesis and said that elimination would occur.

My prof gave me these hints/notes : Check the specific system noted and contemplate the involvement of anchimeric assistance in the formation of an unusual product


I thought i nailed it with the elimination happening but now im at a complete lost!
 

[discodermolide]

Here is a suggestion, what do you (and others) think?

[laze]

Here is a suggestion, what do you (and others) think?

The answer i submitted was is  2-methoxy-cyclohex-1-ene. So i probably did something wrong during my mechanism.
I keep looking back to the question and it said the "observed substituted product." I don't know how its going through substitution.

[discodermolide]

Well I suppose it's a substitution of th Cl by the oxygen lone pair followed by an elimination.
I don't see where the Williamson ether synthesis fits in!

[laze]

Well I suppose it's a substitution of th Cl by the oxygen lone pair followed by an elimination.
I don't see where the Williamson ether synthesis fits in!

Ah i see, and then the lone pairs on that oxygen would be what contributing anchimeric assistance. I think the whole point of the Williamson ether synthesis being there would be that, if everything went smoothly without any interference from any other phenomena then an ether would be formed. But since there are other contributing factors, it just isnt true. The mechanism you drew put things together for me. The scrappy one i made didn't involve the lone pair on the methoxide oxygen on the ring, in which i produced my initial elimination product.

I want to think that the mechanism you suggested is correct. I need to look up articles about anchimeric assistance and how it can impact WES and such, as i cannot find it in my current ochem textbook.

[orgopete]

I presume the product is trans-1,2-dimethoxycyclohexane upon opening of the oxiranium ring. My comments were not directed to providing a substitution product, but what one should reasonably expect. You would also get trans-1,2-dimethoxycyclohexane if the reaction were carried out in methanol without NaOMe. It would be easier to predict that as the product as those conditions are more easily understood as SN1 conditions. If the reaction is an SN1 mechanism, then NaOMe is not a kineticly important reagent nor a catalyst. It may well have been present, but in this case misleading to predicting the product.