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Question about Delocalisation of Carboxylic Acid and Acctactiveness to Proton

  1. Jan 7, 2012 #1
    So I understand that when you deporotonate a carboxylic acid, you get a RCOO-. This causes a delocalisation in the two oxygen atoms. I read somewhere that because of this delocalisation, it makes it less attractive to Hydrogen ions (protons). This makes the carboxylic acid more stable and thus, a stronger acid.

    My question is why the hydrogen ion is less likely to reattach. If protons are positively charged, won't there be some kind of attraction to the negatively charged anion of carboxylic acid?

    Thank you.
  2. jcsd
  3. Jan 7, 2012 #2
    You sorta answered it yourself. Think about charge delocalization. It stabilizes the anion and that stabilization makes it less reactive than it would be as a full, singular anion.

    The delocalization makes both of the oxygen atoms have a partial negative charge, as opposed to only one of them having a full negative, which would be more reactive.
  4. Jan 8, 2012 #3


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    Staff: Mentor

    You can think about it this way - delocalized charge does attract the proton, but it doesn't attract it to a single place in the COO- group, so it can "touch" the group in any place, not necessarily in the place it can be attached. Very hand-wavy argument, but may help.
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