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Stupid, Stupid Spectroscopy.

Discussion in 'MCAT Discussions' started by Kikaku21, Aug 4, 2006.

  1. Kikaku21

    Kikaku21 Senior Member
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    Ok. So how much do we REALLY need to know? H NMR. Which groups should I memorize?? I HATE THIS STUFF.

    I understand that for UV you can get away with knowing that Carbonyl groups are around 1700 along with amines and that hydroxyl groups are around 3500.
     
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  3. jsol

    jsol Member
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    the biggest one for H0nmr is the aldehyde deshielding at 9.5 ppm, and also know that whenever a hydrogen is near a electron withdrawing group like oxygen, that it is going to be further downfield (to the left). Other than that you should be ok. Oh I got a C-NMR question on aamc 8 and it was to know that aldehydes and ketones at around 170 ppm. hope that helps
     
  4. dctrgreen

    dctrgreen Junior Member
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    yeah...spectroscopy is not my favorite topic either. so far for me, just knowing the very basics has worked for me on practice tests (-OH and carbonyl groups). the questions i have seen have all been pretty basic. i have yet to come across anything that required further knowledge beyond that (theory of stretching molecules and all that jazz)

    just know the basic functional group peaks and i think you will be ok. ;)
     
  5. DrBowtie

    DrBowtie Final Countdown
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    Was it point blank, Where do you expect to find the peak?
     
  6. doublehh03

    doublehh03 Senior Member
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    for spectroscopy, knows -OH, amines, carbonyl and you're set
     
  7. luckycharms08

    luckycharms08 all it takes is one =)
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    that's for IR spec, not UV spec
     
  8. Kikaku21

    Kikaku21 Senior Member
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    Yeah. I remember the question. Its point blank. Seems like you could eliminate one answer because is was totally off the mark.
     
  9. Kikaku21

    Kikaku21 Senior Member
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    You're right. My bad.
     
  10. DrBowtie

    DrBowtie Final Countdown
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    I would guess it would be the biggest value.
     
  11. Kikaku21

    Kikaku21 Senior Member
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    Right. That was the logic I used and got the question correct... Still a little unnerving though.. What if the throw in a random high value just to trip you up, make sure you really know the number.... Ugh.
     
  12. WilliamsF1

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    Are you sure the aldehydes and ketones are at 170? I thought carboxylic acids where around there. 200-210 is ketones and aldehydes I think. Someone please correct me if I'm wrong.

    Edit: BB, are you saying that it's the biggest value because the oxygen is withdrawing e- making less shielding?
     
  13. Kikaku21

    Kikaku21 Senior Member
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  14. jsol

    jsol Member
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    sorry aldehydes are around 170 and ketons are around 200. Its was more a generalization thats its likely going to be the largest number. I doubt that they give answer choices of say 200, 180 and 170. The answer should be clear cut.
     
  15. DrBowtie

    DrBowtie Final Countdown
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    Yeah that was my logic.
     
  16. ChymeChancellor

    ChymeChancellor Membership Revoked
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    This is not stressed too much on the MCAT.... with only one or two passages devoted to organic and a few discretes, there isn't really much room for that much detail for memorization. Just know the major peaks in IR. You can pretty much eyeball the NMR if you know a few simple rules.... (symmetry, electron withdrawing groups).
     
  17. Summer Sweet

    Summer Sweet Le chéri, c'est la vie
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    You mean IR, not UV, right?

    For IR, I had to learn them all in wavelengths/microns because my professor was old school, and memorized microns the way they did it 30 years ago...so now, I have to relearn everything in frequency/wavenumbers...*sigh*

    NMR isn't too bad, if you just know the basics. I think generally, know CH3, CH3, CH, aromatic, and maybe attached to carbonyl ones. And then, know the principle--that electron withdrawing groups are deshielding, and thus push your peaks further downfield. On the other hand, shielding groups would push your peaks upfield. Concepts > Numbers, was always my philosophy :)
     

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