DAT DESTROYER 2010 Orgo Chem #39

[Felix24]

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Can anyone help me with this problem?

I'm not sure why the H+ on the methyl group of the carbonyl is more acidic than the H+ in the middle of the molecule (right on the other side of the carbonyl)? I thought the answer was A because of inductive effect by the left oxygen while choice B (the correct answer) does not have as much inductive effect by the left oxygen.

 

[Dotoday]

When you pull of an alpha proton, you get resonance stabilization of the anion. This will increase acidity. Hope this helps.

Sent from my MB855 using Tapatalk

 

[Felix24]

For this specific question, however, both choices have a H+ proton coming off of alpha carbons on either side of the carbonyl meaning they both do resonance stabilization of the anion. However, another oxygen (that does not contribute to resonance) is closer to the H+ in choice A (the wrong answer) than the H+ in choice B (the right answer) so shouldn't better induction + resonance make LDA deprotonate choice A not B??

Anyone?

 

[mk4]

Can you post up the picture/question? I'm having some difficulty visualizing what you're describing.

For this specific question, however, both choices have a H+ proton coming off of alpha carbons on either side of the carbonyl meaning they both do resonance stabilization of the anion. However, another oxygen (that does not contribute to resonance) is closer to the H+ in choice A (the wrong answer) than the H+ in choice B (the right answer) so shouldn't better induction + resonance make LDA deprotonate choice A not B??

Anyone?