Spectroscopy/Spectrometry

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omi14
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123503
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Spectroscopy/Spectrometry
Updated:
2011-12-13 19:21:29
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spectroscopy spectrometry proton nmr carbon 13 ir infrared mass organic chemistry CHM 325
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CHM 325 Organic Chemistry
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  1. In Ultraviolet-Visible(UV-Vis) spectroscopy, a molecule is treated with ultraviolet-visible light to excite and electron and causes _____ (the molecular effect)
    electronic transition
  2. In infrared spectroscopy, absorption of infrared light by a molecule causes _____ (molecular effect)
    molecular vibration
  3. In nuclear magnetic resonance spectroscopy, absorption of radio frequency by a molecule causes _____ (molecular effect)
    nuclear spin transition
  4. Which spectroscopy causes electronic transition?
    Ultraviolet-visible spectroscopy
  5. Which spectroscopy causes molecular vibration?
    Infrared spectroscopy
  6. Which spectroscopy causes nuclear spin transition?
    Nuclear magnetic resonance spectroscopy
  7. What light is used in infrared spectroscopy?
    infrared light
  8. What light is used in nuclear magnetic resonance spectroscopy?
    radio waves
  9. What happens in mass spectrometry?
    A molecule is ionized and broken apart into more ions (fragments).
  10. How do you calculate element of unsaturation?
    What is 1 element of unsaturation?
    What is 2?
    • [2(number of C + 0.5 number of N)+2-(number of H + number of halogens)]/2
    • 1 = ring or double bond
    • 2 = triple bond
  11. IR spectrum: Why are peaks broad for O-H and N-H?
    Hydrogen bonding allows for different enviornments (ex: variances in strength of H bond vibrations, dimerization) and causes the molecules to absorb different lights.
  12. Why are absorptions of C=O for amides lower than other C=O bonds?
    Amides don't have a full C=O bond due to resonance structures so we see a lower rate number.
  13. IR spectrum: How does conjugation effect absorbance?
    Conjugation is when multiple bonds can alternate into single bonds (resonance structures). Conjugated molecules do not have full C=O bonds so they have lower rate number.
  14. Mass spectrometry: What is M+?
    • Molecular ion
    • Found at mass of the molecular ion on the spectrum
  15. Mass spectrometry: How do you identify Cl?
    M++2 is a third of M+ peak
  16. Mass spectrometry: How do you identify Br?
    M++2 is as large as M+ peak
  17. Mass spectrometry: How do you identify S?
    M++2 is larger than 4% of M+ peak (not as clear as Br or Cl)
  18. Mass spectrometry: How do you identify I?
    Peak at 127 or fregment that is M+-127
  19. Mass spectrometry: How do you identify a loss of an alcohol?
    A peak at M+-18
  20. NMR: Absorption on the left of the spectrum is referred to as _____
    Downfield or deshielded
  21. NMR: Absorption on the right of the spectrum is referred to as _____
    Upfield or shielded
  22. What is TMS and what is its structure?
    • Tetramethylsilane
    •  
  23. 1H NMR: What is the ppm of H next to a saturated center?
    0-1.5 ppm
  24. 1H NMR: What is the ppm of H next to an unsaturated center or an acetylenic H?
    1.5-2.5 ppm
  25. What is acetylene?
    • 
    • (red is acetylenic hydrogen)
  26. 1H NMR: What is the ppm of H next to a highly electronegative atom (O, N, halides)?
    2.5-4.5 ppm
  27. 1H NMR: What is the ppm of a vinylic H (C=C-H)?
    4.5-6.5 ppm
  28. 1H NMR: What is the ppm of an aromatic H?
    6.5-8.0 ppm
  29. 1H NMR: What is the ppm of an aldehyde H (O=C-H)?
    9-10 ppm
  30. 1H NMR: What is the ppm of a carboxylic acid proton (O=C-O-H)?
    10-12 ppm
  31. 1H NMR: What is the n+1 rule?
    The number of splits is number of H on the adjacent center causing splitting (n) + 1
  32. 13C NMR: What is the ppm of a Csp3?
    0-100 ppm
  33. 13C NMR: What is the ppm of a Csp2?
    100-210 ppm
  34. 13C NMR: What is the ppm of a C=O of amide/ester/carboxylic acid?
    160-180 ppm
  35. 13C NMR: What is the ppm of a C=O of ketone/aldehyde?
    180-210 ppm
  36. 13C NMR: What is the ppm of sp hybridized C?
    65-95 ppm

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