Chapter 13 lecture Flashcards
What does Mass Spectrometry do
Determines molecule weight and molecule formula of a compound
What is Mass Spectrometry
Molecule Vaporized and ionized by bombardment with beam of high energy electrons
What does the electron beam do when using mass spectrometry?
causes a molecule to eject electron
What does the Mass spectrometer make?
radicals and cations
What is the tallest peak
Base peak
Nitrogen rule
odd molecular ions contain odd number of N while even number of N have even molecular ions
Alkyl chloride special
3:1 ratio for molecular ion
Alkyl bromides
1:1 ratio for molecular ion
What does a large molecule mean for fragments
more fragments
Aldehydes certain fragmentation patterns
alpha cleavage: Next to C with O on it
Ketones certain fragmentation patterns
alpha cleavage: Next to C with O on it
Alcohols certain fragmentation patterns
alpha cleavage and dehydration (elimination of water)
Infrared Spectroscopy
used to identify bonds and functional groups in compound
discuss wavelength and frequency
inversely proportional
Wavelength increase= frequency decreases
What happens when IR light is absorbed by bonds
2 atoms a bond can stretch and 3 bonds can bend
How to know if IR light is absorbed
frequency of bond stretching matches frequency of IR so light is absorbed
What is the functional group region
4000-1500 wavenumber
what is the fingerprint region
1500 and down
What is wavenumber proportional to
frequency
X axis of IR
wavenumbers
Y axis of IR
transmittance
100% vs 0% transmittance
100% all light went through sample
0% all light absorbed
What properties affect IR absorption
bond strength and atom mass
Stronger bonds
higher frequency
lighter atoms
higher frequency
4000-2500 wavenumber
bonds to hydrogen
2500-2000
triple bonds
2000-1500
double bonds
1500-400
single bond/ fingerprint region
how does s character affect IR
higher s character % means stronger bond means higher wavenumber
O-H wavenumber and intensity
3600-3200 and strong/broad
N-H wavenumber and intensity
3500-3200 and medium
Csp3-H wavenumber and intensity
3000-2850 and strong
Csp2-H wavenumber and intensity
3150-3000 and strong
Csp-H wavenumber and intensity
3300 and medium
C triple C wavenumber and intensity
2250 and medium
C triple N wavenumber and intensity
2250 and medium
C=O wavenumber and intensity
1800-1650 and strong
What does the increase of s character do to the wavenumber
increase the wavenumber
For IR absorption to work what must a molecule have?
dipole moment
