Ch 12 Ppt 1

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DesLee26
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259836
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Ch 12 Ppt 1
Updated:
2014-02-02 16:50:47
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CHM 202
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Organic Chemistry
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  1. __is an analytical technique which helps determine structure.
    It destroys little or no sample.
    The amount of light absorbed by the sample is measured as __is varied. 
    • Spectroscopy
    • wavelength
  2. __ measures the bond vibration frequencies in a molecule and is used to determine the functional group.
    •__  fragments the molecule and measures the masses.
    • Infrared (IR) spectroscopy
    • Mass spectrometry
  3. •__spectroscopy detects signals from hydrogen atoms and can be used to distinguish isomers.
    __ uses electron transitions to determine bonding patterns. =>
    • Nuclear magnetic resonance (NMR) 
    • Ultraviolet (UV) spectroscopy
  4. __, where c is the __.
    Energy per photon = __, where h is Planck’s constant.                               
    • c = λv
    • speed of light
    • hv
  5. •__ is just below red in the visible region.
    Wavelengths usually 2.5-25 mm.
    More common units are __, or cm-1, the reciprocal of the wavelength in centimeters.
    Wavenumbers are proportional to frequency and energy.                        
    • The IR region
    • wavenumbers
  6. If stretched,, where is the spring force?
    if compressed, where?
    • spring force is in 
    • spring force is out
  7. Frequency decreases with __.
    Frequency increases with __.
    • increasing AW
    • increasing bond energy
  8. __ are also quantitized.
    No two molecules will give exactly the same __

    Simple stretching:  1600-3500 cm-1.
    Complex vibrations:  600-1400 cm-1, called the “__region.”
    • Whole-molecule vibrations and bending vibrations 
    • IR spectrum (except enantiomers).
    • fingerprint
  9. A polar bond is usually __.
    A nonpolar bond in a symmetrical molecule will absorb __.
    • IR-active
    • weakly or not at all.
  10. What are the C-C bond frequencies?

    Conjugation?
    • C-C (1200)
    • C=C (1660)
    • C***C (2200)

    • isolated C=C (1640-1680)
    • conjugated C=C (1620-1640)
    • aromatic C=C (1600)
  11. Carbon Hydrogen bond stretches
    • C-H 2800-3000
    • =C-H 3000-3100
    • ***C-H 3300
  12. Both OH and NH occur around __, but what's the differences.
    3300

    • Alcohol OH is broad with a rounded tip
    • Secondary amine is broad with one sharp spike
    • Primary amine is broad with two sharp spikes
    • no signal for tertiary
  13. The C=O bond of simple ketones, ald., and carb acids absorb around __.


    Usually, its the __. 

    __ will also have OH. 

    __ have two CH signals around __.
    1710

    strongest IR signal

    carb acids

    aldehydes

    2700 and 2800 cm-1
  14. Conjugation of C=O with C=C lowers the stretching frequency to ~__cm-1.
    The C=O group of an __absorbs at an even lower frequency, __.
    • 1680 
    • amide 
    • 1640-1680 cm-1
  15. The C=O of an __absorbs at a higher frequency, ~__cm-1.
    • ester 
    • 1730-1740
  16. Carbonyl groups in __absorb at an even higher frequency
    small rings (5 C’s orless)
  17. C-N absorbs around __
    C=N absorbs around __ and is much stronger than the __ in teh same region.
    C *** N absorbs strongly just __. The alkyne C  C signal is much weaker and is just __ . =>
    • 1200 cm
    • 1660 
    • C=C
    • above 2200
    • below 2200
    • below 2200 cm-1
  18. The absence of a signal is definite proof of what?
    that the functional group is absent

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