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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: asd5110 on December 17, 2010, 03:51:46 AM

Title: epoxide opening
Post by: asd5110 on December 17, 2010, 03:51:46 AM

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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

Title: Re: epoxide opening
Post by: bromidewind 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.

Title: Re: epoxide opening
Post by: orgstudy 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!!!

Title: Re: epoxide opening
Post by: Doc Oc 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.