Orgo question

[adamrose]

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I thought an aldol condensation always creates a bond between the alpha and beta carbons and dehydrates?

#44

Would the question have to specify that DeltaH is added in order to create the double bond? Im confused

 

[yihaej12]

I thought an aldol condensation always creates a bond between the alpha and beta carbons and dehydrates?

#44

Would the question have to specify that DeltaH is added in order to create the double bond? Im confused

Yes! without heat, you don't get the loss of H and OH that would create the double bond.

 

[Mr.Mike]

To add on to what yihaej12 said ......

In an aldol condensation reaction you would get the dehydration product without heat if the product is an extremely stable compound I.e.- highly conjugated
But in a regular case, you would need heat to dehydrate as previously mentioned.

 

[ThunderSplash]

Heat is required to form the double bond, I'm pretty sure. I would treat the product as an alcohol.... and what do you need to make an alcohol undergo elimination? Heat!

Also, don't forget secondary and tertiary alcohols usually proceed through E1 and primary alcohols proceed through E2!

 

[DAT Destroyer]

I thought an aldol condensation always creates a bond between the alpha and beta carbons and dehydrates?

#44

Would the question have to specify that DeltaH is added in order to create the double bond? Im confused

Do not be confused 😕

Here is the bottom line......Normally heat is needed after the base-catalyzed reaction to form the alpha-beta unsaturated carbonyl product. It is often very desirable to have the reaction proceed to this type of compound , for synthetic purposes.

If you are near a benzene ring....the reaction normally proceeds further to the alpha-beta unsaturated carbonyl compound even without heating.

Why ?

Because the product is extensively conjugated which means it is very stable. The driving force being the formation of a conjugated system. The Paula Yourkanis Bruice text gives some nice examples if you need more details.

Hope this helps

Dr. Romano

 

[adamrose]

Do not be confused 😕

Here is the bottom line......Normally heat is needed after the base-catalyzed reaction to form the alpha-beta unsaturated carbonyl product. It is often very desirable to have the reaction proceed to this type of compound , for synthetic purposes.

If you are near a benzene ring....the reaction normally proceeds further to the alpha-beta unsaturated carbonyl compound even without heating.

Why ?

Because the product is extensively conjugated which means it is very stable. The driving force being the formation of a conjugated system. The Paula Yourkanis Bruice text gives some nice examples if you need more details.

Hope this helps

Dr. Romano

Ugh more things to consider. Thank you though