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Topic: epoxide opening  (Read 3713 times)

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Offline asd5110

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epoxide opening
« on: December 17, 2010, 03:51:46 AM »



Which set of reagents is the best to accomplish the transformation shown above?
A) CH3CH2I/KOH
B) CH3OCH2CH3/H3PO4
C) CH3CH2OH/H2SO4
D) CH3CH2MgBr/ether
E) CH3CH2OK/CH3CH2I

i guessed C but i don't know why the other answer choices wouldn't work
« Last Edit: December 17, 2010, 04:02:06 AM by asd5110 »

Offline bromidewind

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Re: epoxide opening
« Reply #1 on: December 18, 2010, 06:24:56 AM »
I think C is wrong because while it fits the requirements of alcohol + acid, it would yield a different isomer. Not sure without actually working the problem out.

Grignard reagents work quite well with epoxide ring openings due to their nucleophilic nature. You might want to give that a shot.

Offline orgstudy

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Re: epoxide opening
« Reply #2 on: December 18, 2010, 09:54:41 AM »
Grignard wont work. it will attach C2H5 not OC2H5.

Not even A and E as it will give addition if I.

B, C both will work but i guess B will give OCH3 addition rather than OC2H5 addition as major product.

So i think C is most appropriate. :)

correct me if i'm wrong!!!
Chemistry is a subject in which even the Professor can get confused at any time.

Offline Doc Oc

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Re: epoxide opening
« Reply #3 on: December 18, 2010, 04:47:11 PM »
C is the correct answer.  Many of the other conditions won't even yield the correct product, so you can eliminate them based on that.  The reason C is correct is that under acidic conditions, the epoxide will open to yield a carbocation.  In the epoxide shown, there are two possible carbocations and one is more stable than the other.  You should be able to finish from there.

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