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Can someone please explain NMR and which hydrogen is most acidic?

Discussion in 'DAT Discussions' started by teefRcool, Jul 17, 2006.

  1. teefRcool

    teefRcool Senior Member
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    Can someone please explain NMR and which hydrogen is most acidic?

    I'm seriously lost with those could someone please explain how those work and how to pick which hydrogen is most acidic when given a huge molecule.

    NMR i'm lost about how many peaks etc..?

    Thanks a bunch if someone could help me out.
     
  2. midwestboy

    midwestboy Member
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    The most acidic hydrogen is usually the hydrogen located closest to the most electronegative or electron withdrawing atom. ie the Hydrogen attached to oxygen in alcohols or acids.
     
  3. OP
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    teefRcool

    teefRcool Senior Member
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    so what if you have ketone in the middle of a chain then what?
     
  4. allstardentist

    allstardentist All-Star
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    if i remember correctly, the alpha hydrogens are most acidic
     
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  5. orgoman22

    orgoman22 DAT DESTROYER
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    The best way that I teach all my students about acidity is first to recall general guidlines..... Carboxy Acids > Phenols > alcohols > alkynes > alkenes > alkanes. while esters, ethers, and amides are not very acidic at all. I think that should help for the DAT. Now, what if there is a ketone or aldehyde ? The pka of an alcohol is about 16, while the aldehyde or ketone is about 20, thus less acidic. If a double alpha proton is present such as in 1,3- cyclohexanone, it would be more acidic because of resonance stabilization of the anion by both carbonyl groups. In Acetoacetic ester, look up the structure in your Orgo book, you would note that the double alpha proton has a pKa of 11, much more acidic than an alpha proton. I hope that helps

    Regards Dr. Jim Romano NYU
     
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