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Photon336

  • one year ago

Organic chemistry question

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  1. Photon336
    • one year ago
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    A nice question about acidity

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  2. dessyj1
    • one year ago
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    I believe the answer would be C

  3. dessyj1
    • one year ago
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    I am not entirely sure, though. Esters, for sure, are more acidic than alkanes, and I choose option C over option A because I having more than one branched functional group weakens the acidity of the structure.

  4. dessyj1
    • one year ago
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    What do you think?

  5. Photon336
    • one year ago
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    |dw:1437680730609:dw| Let's look at the alkane first. like it would be so hard to pull off a Hydrogen form the end because that molecule wouldn't really be stable. well.. unless it was let's say if we used like grinard reagent. I think actually that the Ka for this molecule would be so small and, correspondingly it's pKa so high that, that proton wouldn't even be able to be pulled off. so like we obviously know that that one isn't possible so that's out.

  6. Photon336
    • one year ago
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    @dessyj1 have you heard of ARIO?

  7. Photon336
    • one year ago
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    for ranking compounds based on acidity we take into account ARIO so in order it would be: Atom Resonance Induction Orbitals

  8. dessyj1
    • one year ago
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    I have not heard of ARIO. My knowledge of organic chemistry only goes a far as high school.

  9. dessyj1
    • one year ago
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    Those compounds are organic compounds, right?

  10. Photon336
    • one year ago
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    |dw:1437681138719:dw| You are right that the first molecule I would be acidic; but let's also look at the third compound and yes you're also right they're organic

  11. Photon336
    • one year ago
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    So for ARIO we use that to rank compounds in terms of acidity so we consider first the atom were dealing with, then if there is any resonance, induction, and then orbitals. I'm not too keen on orbitals though. but the idea is that an acid does one thing A. GIVES Up a proton B. Has a negative charge a better acid is one that: can stabilize the negative charge better. a more stable negative charge = it's a better acid and it won't want to take that proton back. this can be done with the size of the atom Resonance Induction things like that.

  12. Photon336
    • one year ago
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    |dw:1437681448511:dw| you'll probably learn about this later, but don't think its covered in HS as much, but there are certain protons/hydrogens that can be removed from a compound

  13. dessyj1
    • one year ago
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    So, because the di-ester will be more comfortable with losing a hydrogen, it is- in turn - more acidic?

  14. Photon336
    • one year ago
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    yeah, i think that's (di ketone) if i remember correctly

  15. Photon336
    • one year ago
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    i'll show you the hydrogens

  16. Photon336
    • one year ago
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    |dw:1437682141969:dw| those would be the hydrogenates that would be removed most easily. you could take off the others as well. you know how mechanisms work yet or no?

  17. Photon336
    • one year ago
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    say if we had a strong base or something. |dw:1437682535300:dw| it would pull off the proton from that molecule, right in the middle of those two carbonyl groups. the arrow just shows us where the electrons are going, while the R could mean any group.

  18. Photon336
    • one year ago
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    |dw:1437682622691:dw| see what I did there?

  19. Photon336
    • one year ago
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    Think of the oxygens as, they have a high electronegativity so the negative charge is happy there, and it's stable.

  20. Photon336
    • one year ago
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    You can also move that negative charge around too, because of resonance

  21. Photon336
    • one year ago
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    and resonance makes it more stable.

  22. Photon336
    • one year ago
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    ok another question what if i had something like this

  23. Photon336
    • one year ago
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    |dw:1437683203892:dw| These two molecules illustrate something called induction

  24. Photon336
    • one year ago
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    The \[CF _{3}\] group is very electronegative so its going to pull electron density from the - charge on that oxygen once you lose the proton. and it's going to be more stable

  25. Photon336
    • one year ago
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    But the catch is, for induction the longer the distance it is, it's effect doesn't really matter it goes down

  26. Photon336
    • one year ago
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    so based on that which one would be more acidic ?

  27. dessyj1
    • one year ago
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    The structure with the shorter carbon chain due to induction?

  28. dessyj1
    • one year ago
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    And I was mistaken, that was not an ester.

  29. Photon336
    • one year ago
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    exactly

  30. Photon336
    • one year ago
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    induction, in this case is like if you have highly electronegative atoms or groups that are in close proximity to part of the molecule where your acidic proton is.

  31. dessyj1
    • one year ago
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    Ah, okay. Nice. Thank you. I learned something new. One more question. In regards to the longer carbon chained structure, it would be best to take a hydrogen from the carbon closest to the tri-bromomethane group right?

  32. Photon336
    • one year ago
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    Hey can you draw that out? I'll be happy to help

  33. dessyj1
    • one year ago
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    |dw:1437686943622:dw|

  34. Photon336
    • one year ago
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    good question.. |dw:1437687292922:dw| hm.. I guess you could do this like take off a negative charge from the carbon near the CF3 Group but it would be hard, I guess you would need a really strong base to do that.

  35. Photon336
    • one year ago
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    if we looked at that molecule you drew there are 3 hydrogens that could possibly be pulled off.

  36. dessyj1
    • one year ago
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    By the way, I put the negative charge in place of the hydrogen I had pulled out as a example. That was the hydrogen I wanted to pull off.

  37. Photon336
    • one year ago
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    oh i see, I think that's possible b/c the flourines could stabilize the negative charge. @empty hey what do you think about this?

  38. Photon336
    • one year ago
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    I still think that it's possible, b/c of those fluorine groups would stabilize that - charge though

  39. dessyj1
    • one year ago
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    Ok, and if you took a hydrogen near the cooh group, the cooh group would stabilize the charge as well?

  40. Photon336
    • one year ago
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    yeah, but I think that the most acidic proton would be the one on the OH group, but I think you can also take those ones off too.

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