quick question about grignard adding to epoxides

[spoog74]

if there is an epoxide that has a TERTIARY carbon, ( under acidic conditions) would it be safe to assume the nucleophile adds to the teritary carbon?

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[bharat008]

if there is an epoxide that has a TERTIARY carbon, ( under acidic conditions) would it be safe to assume the nucleophile adds to the teritary carbon?

You can add nucleophile in acidic conditions to MORE SUBSTITUTED Carbon of epoxide
For ex: CH3OH/ACID = CH3O- would attack on the more substituted carbon

If you have grignard (from Alkyne) then you always attack on the LESS SUBSTITUTED b/c if you have acid then the grignard would steal the H and then it wouldn't be a nucleophile, so no rxn would occur with epoxide.

 

[Jab1113]

You can add nucleophile in acidic conditions to MORE SUBSTITUTED Carbon of epoxide
For ex: CH3OH/ACID = CH3O- would attack on the more substituted carbon

If you have grignard (from Alkyne) then you always attack on the LESS SUBSTITUTED b/c if you have acid then the grignard would steal the H and then it wouldn't be a nucleophile, so no rxn would occur with epoxide.

So in acidic conditions, you go for the more substituted side but in basic conditions you attack the least substitued side? Is that correct?

 

[bharat008]

So in acidic conditions, you go for the more substituted side but in basic conditions you attack the least substitued side? Is that correct?

Yes.
The only exception being acetylide nucleophile. If you have acetylide nucleophile in acidic conditions it would steal the H from acid and then it wouldn't attack the epoxide..

 

[Jab1113]

Yes.
The only exception being carbon nucleophile. If you have carbon nucleophile in acidic conditions it would steal the H from acid and then it wouldn't attack the epoxide..

what reagent would tell you that its acidic?

H2SO4?

 

[lyjw88]

what reagent would tell you that its acidic?

H2SO4?

If H2SO4 is present with the nucleophile, then yes it is an acidic environment.

 

[Jab1113]

I gotta study my orgo reactions asap lol

 

[Jab1113]

You can add nucleophile in acidic conditions to MORE SUBSTITUTED Carbon of epoxide
For ex: CH3OH/ACID = CH3O- would attack on the more substituted carbon

If you have grignard (from Alkyne) then you always attack on the LESS SUBSTITUTED b/c if you have acid then the grignard would steal the H and then it wouldn't be a nucleophile, so no rxn would occur with epoxide.

I have a question about this grignard-epoxy reaction then which is in the 2011 Destroyer on page 112 Road Map 6 at the bottom, the epoxide is reacting with H3O+ (acidic) but attacks the least substituted carbon and not the most substituted.

Is this an error?

Uploaded picture: http://i1136.photobucket.com/albums/n488/Jab1113/WP_000322.jpg

 

[lyjw88]

I have a question about this grignard-epoxy reaction then which is in the 2011 Destroyer on page 112 Road Map 6 at the bottom, the epoxide is reacting with H3O+ (acidic) but attacks the least substituted carbon and not the most substituted.

Is this an error?

Uploaded picture: http://i1136.photobucket.com/albums/n488/Jab1113/WP_000322.jpg

It's not an error because grignard was added first and after this rxn was done, then H3O+ was added.

 

[Jab1113]

It's not an error because grignard was added first and after this rxn was done, then H3O+ was added.

+1 👍 thanks

 

[Jab1113]

Definitely just watched Chads video on Ethers/Epoxides and realized I fell for the grignard trap so thank you lyjw88 and bharat008 for all the help!

 

[lyjw88]

Definitely just watched Chads video on Ethers/Epoxides and realized I fell for the grignard trap so thank you lyjw88 and bharat008 for all the help!

No prob! Good luck studying.