VSEPR_VOID
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Addition of HCl to Propenoic acid
I am on chapter 6 of my orgo book and unfortunately the AP chem teacher at my high school recently quite his job. I already asked a uni student who is
taking some chem courses and I have yet to receive an expiation for this reaction. I also googled the problem and came up with no answers or
explanations. Help me Science Madness you are my only hope.
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LearnedAmateur
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I found this on the Wikipedia article for 'nucleophilic conjugate addition'. I know it's not the same mechanism as what is occurring here, but it
would explain why only the 3-chloro isomer is formed. Hopefully more insight and/or improvements will come this way, it's peaked my interest now.
[Edited on 9-12-2017 by LearnedAmateur]
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ninhydric1
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I would assume LearnedAmateur's mechanism is correct, as only HBr can undergo free-radical addition, ending in a product opposing Markovnikov's rule.
Another one of the many exceptions in organic chemistry  .
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DJF90
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Quote: Originally posted by LearnedAmateur  | I know it's not the same mechanism as what is occurring here, but it would explain why only the 3-chloro isomer is formed.
[Edited on 9-12-2017 by LearnedAmateur] |
What makes you say that?
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VSEPR_VOID
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Thank you. I worked out mechanism on paper and it seems to work.
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LearnedAmateur
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Propenoic acid contains an a,b unsaturated carbonyl, which is what is required for this particular reaction. I know that the hydroxyl group generates
a resonance structure which could mean a completely different mechanism, but this is the closest thing I can find.
In chemistry, sometimes the solution is the problem.
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DraconicAcid
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Since chloride isn't that great of a nucleophile, I wouldn't be surprised if the first step was the protonation of the carboxylic acid group, which
would give a cation that would resonate and put some positive charge on the beta carbon.
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Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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VSEPR_VOID
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Could anyone help me with this problem as well? Thanks.
[Edited on 10-12-2017 by VSEPR_VOID]
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