Ochem Question!!!

[Franksta1118]

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Hey, this is from the ICC from TPR passage 9 of OCHEM question 8 for those of you who have the 2008 materials:

We are looking for the product formed by the thermodynamic enolate of 2-methyl-cyclohexanone rxted with D30+.

I would deprotonate the hydrogen adjacent to the carbonly that doesn't have the extra methyl group because this would lead to the more stable enolate, there would be no inductive effect from the methyl group. BUT, the answer they have deprotonated the hydrogen from the carbon with the methyl group. Is this because they threw the word thermodynamic in there? Are they trying to show that the Zaitsev alkene would be favored even though there is an inductive effect destabilizing the enolate? I hope i didn't confuse everybody!

 

[BloodySurgeon]

I don't have TPR book but the answer is because that is the thermodynamically favored product. 2-methylcyclohexenol is more stable than 3-methylcyclohexen-2-ol and in general, for cycloalkenes, the double bond with the more substituents is more stable.

 

[iA-MD2013]

Hey, this is from the ICC from TPR passage 9 of OCHEM question 8 for those of you who have the 2008 materials:

We are looking for the product formed by the thermodynamic enolate of 2-methyl-cyclohexanone rxted with D30+.

I would deprotonate the hydrogen adjacent to the carbonly that doesn't have the extra methyl group because this would lead to the more stable enolate, there would be no inductive effect from the methyl group. BUT, the answer they have deprotonated the hydrogen from the carbon with the methyl group. Is this because they threw the word thermodynamic in there? Are they trying to show that the Zaitsev alkene would be favored even though there is an inductive effect destabilizing the enolate? I hope i didn't confuse everybody!

Exactly...you answered your own question 😛 Be careful with kinetic vs thermo products.

 

[tweaked17]

Another thing to consider with kinetic/thermo questions is sterics and the reagents you're using. It's why LDA will give you the kinetic product while the thermodynamic product can be achieved through an unhindered base like hydroxide.

I agree that it's the resonance structure of the more substituted alkene that makes that molecule the thermodynamic intermediate in this reaction.