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This is the answer to chapter 22, problem number 60 from the smith organic chemistry textbook.
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And this problem is asking us to draw a stepwise mechanism for the acillation of a particular enzyme by aspirin.
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And so the first step, as is often the case in these kinds of reactions, is going to be this, carbonyl oxygen picking up a proton from this acid catalyst that we're told is present in this reaction.
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And so the oxygen will grab that hydrogen.
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The hydrogen a bond will revert to the a.
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A in this case is just a way of generically representing that it's an acid.
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And so then we'll have this protonated carbonyl oxygen.
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That makes the carbonyl carbon even more electrophilic.
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And so the oh group on this enzyme, probably this is a serene, perhaps.
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So it's one of the amino acids with an oh group in this enzyme.
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So the oh group, the oxygen will act as a nucleophile and attack this electrophilic carbonyl carbon.
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One of these two double bonds will break.
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This will relieve the positive charge on this oxygen.
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And so we have our tetrahedral intermediate that's formed.
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The oxygen that acted as a nucleophile now has a positive charge on it because it has three bonds.
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But we have some a minuses floating around.
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So the conjugate base of the acid that was initially our catalyst for the first step.
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And so this conjugate base can act as a base does and grab this proton.
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The oh bond electrons will revert to the oxygen.
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Now there's no more positive charge on that oxygen.
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And we get to this intermediate, where we have our.....