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Topic: Figuring out a 6 steps reaction mechanism  (Read 2503 times)

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Offline nar_v_mtz

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Figuring out a 6 steps reaction mechanism
« on: April 15, 2016, 10:24:07 PM »
Can somebody help me understand this? Are my suppositions any good? I can’t find any good info on how to solve this. I have attached an image for explanation purposes.

I need to propose a reaction mechanism for the next incomplete reaction. I know some of the mechanisms for the steps shown.

I know that in principle the first step is a substitution, where H attacks Br and the EtO takes its place in the hexanecycle. For the next step, number 3, I have no idea what goes on and how the methyl (CH3) and the EtO change to position 1 of the hexanecycle. I don’t understand either how to go from step 3 to 4, but from 4 to 5 and 6 I suppose the bond its stabilised by resonance, leaving the carbocation in the place from where it’s moving.

Thanks in advance for any help given. This problem gives me a headache.

Offline AWK

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Offline orgopete

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Re: Figuring out a 6 steps reaction mechanism
« Reply #2 on: April 16, 2016, 12:42:49 PM »
Hint, this is an SN1 reaction. Also, the bromine atom of the starting material is as likely to abstract a proton from ethanol as HBr would. It will not happen.
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Offline nar_v_mtz

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Re: Figuring out a 6 steps reaction mechanism
« Reply #3 on: April 16, 2016, 02:39:47 PM »
Thanks to both of you for answer, I appreciate  ;D ;D. Now, I can understand how pass from 1. to 2. it happens a Sn1 reaction, therefore, I'm still lost from the 2. to 3. step  :-\ ??? , what goes on and how the methyl (CH3) and the EtO in the change to position 1 of the cyclohexane, how it's possible pass from ortho to 1,1 position ?  ???
From 3. to 4. happens an elimination, because H and EtO are in trans-diaxial positions and it helps to formation of cyclohexene. Finally I suppose from 4 . to 6. the bond stabilises the cyclohexen by resonance.

I added another image for explains what I did.   :)
Thanks again for any help with this point.  ;D

Offline Babcock_Hall

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Re: Figuring out a 6 steps reaction mechanism
« Reply #4 on: April 16, 2016, 06:51:39 PM »
I would think about relative carbocation stability.

Offline Unco

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Re: Figuring out a 6 steps reaction mechanism
« Reply #5 on: April 27, 2016, 01:45:48 AM »
The carbocation that is formed after bromine leaves is a secondary carbocation, since there's a tertiary site next to this, the carbocation moves to it through hydride shift and forms a tertiary carbocation, now the ethanol can add back and give you the product.

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