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Topic: Reaction mechanism  (Read 9119 times)

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Offline Kate

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Reaction mechanism
« on: March 09, 2008, 09:58:51 AM »
Hello.
I need some tips on how to write the mechanism of the reaction that occurs when mixing camphene + glacial acetic acid + sulfuric acid. I know that the product is an ester.
Thanks. :)
« Last Edit: March 09, 2008, 10:17:43 AM by Kate »
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Offline Rico

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Re: Reaction mechanism
« Reply #1 on: March 09, 2008, 11:02:00 AM »
Hey Kate

What about protonation of the double bond and then nucleophilic attack, by acetic acid, on the formed carbocation?

Rico
 
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Offline Kate

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Re: Reaction mechanism
« Reply #2 on: March 09, 2008, 11:33:19 AM »
So the product would be isobornyl acetate, right ?
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Offline Rico

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Re: Reaction mechanism
« Reply #3 on: March 09, 2008, 01:33:55 PM »
Yes, that's correct! I have drawn the mechanism in a jpeg attached. Do you know what kind of reaction step number two is?

Rico
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Offline Kate

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Re: Reaction mechanism
« Reply #4 on: March 09, 2008, 01:47:43 PM »
I'd say a nucleophilic substitution reaction, but I'm not sure.
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Offline Rico

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Re: Reaction mechanism
« Reply #5 on: March 09, 2008, 02:09:10 PM »
It has nothing to do with a substitution reaction. You can say that you have overall done an addition reaction of acetic acid, but it was more the individual steps in the mechanism i was looking for. The first step is a simple protonation of the double bond, forming a carbocation intemediate. This carbocation intermediate then rearranges in what is called a Wagner-Meerwein rearrangement (this was what I was looking for in my question), to the second carbocation intermediate. The second carbocation intermediate is then trapped by the nucleophile to give the product.

Rico
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Offline Kate

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Re: Reaction mechanism
« Reply #6 on: March 09, 2008, 02:45:25 PM »
Thanks for explaining. :)

I have another question: when doing a saponification of the isobornyl acetate why can't I simply use an aqueous potassium hydroxide solution, but instead have to use a solution of water,ethanol and KOH ? I know this has something to do with isobornyl acetate not being soluble in water, but I don't know why ethanol is required.
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Offline Rico

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Re: Reaction mechanism
« Reply #7 on: March 09, 2008, 03:03:07 PM »
You have already answered the question yourself! Ethanol is not as hydrophilic as water and therefore isobornyl acetate is more soluble in ethanol. A mixture of water and ethanol therefore more easily solubilizes isobornyl acetate than pure water. It is important that as much isobornyl acetate is dissolved as possible, since the hydroxide ions are also in solution. The more isobornyl acetate that is dissolved, the faster the saponification proceeds.

Rico   
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Offline Kate

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Re: Reaction mechanism
« Reply #8 on: March 09, 2008, 03:09:41 PM »
Oh, I got it now. Thanks. :)
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