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AAMC Organic Chem Mechanism Question?

Discussion in 'MCAT Study Question Q&A' started by stester77s, May 19, 2014.

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  1. stester77s

    stester77s 2+ Year Member

    Feb 4, 2014
    I attached an image of the mechaism in question. My question, is how does the middle oxygen get protonated while the other oxygen has a negative charge? Shouldn't the oxygen with the negative charge get protonated before the neutral oxygen?

    What is the name of this synthesis (so I can look up alternative mechanisms)?

    Attached Files:

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  3. tdod

    tdod 5+ Year Member

    Oct 30, 2011
    my best answer is that the alkoxide oxygen probably does pick up a proton first. however, there is no way to break up the compound, so eventually that proton gets lost. in contrast, when the central oxygen picks up a proton, the compound can collapse and will not reform.
  4. syoung

    syoung MS-3 5+ Year Member

    Jan 2, 2011
    Over the rainbow
    Actually that mechanism looks weird on a couple of levels. What's the solvent? That would determine how the mechanism proceeds.
  5. SuperSneaky24


    Nov 27, 2013
    So my guess is that what you said also occurs (that the negative oxygen is protonated instead). What you'll get is both forms, kind of like a keto-enol tautomerization but not exactly the same. It is the form in the image that is reactive and will cause the forward reaction to occur.

    Found the reaction online, except that hydride shift never occurs, so it's probably not that critical of a step
    syoung and DrknoSDN like this.
  6. DrknoSDN


    Feb 21, 2014
    Nice, I was about to repost the same link as you. It does show a better mechanism.

    To find lots of mechanism pictures just search google images and type all the functional groups... I.E. "Anhydride Amine Amide", pops right up.

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