6. analytical techniques Flashcards
1
Q
how does infrared spectroscopy work
A
- beam of IR radiation passed through sample
- IR radiation absorbed by covalent bonds increasing vibrational energy
- bonds between different atoms absorb different frequencies
- frequency/wavenumber can be used to identify functional groups
2
Q
uses of IR spectroscopy
A
- breathalysers. amount of ethanol in breath measured by intensity of peak
- measures concentration of polluting gases in atmosphere CO and NO (both present in car emissions) intensity of peaks can be studied
3
Q
how does mess spectrometry work
A
- sample bombarded with electrons
- removes an electron from the molecule to form a molecular ion M+(g)
- causes some of molecular ions to break into fragments
4
Q
how to find the Mr from mass spectrometry
A
look at molecular ion peak (M peak)
the mass/charge value of M peak is the Mr
5
Q
for most organic compounds the M peak is
A
the peak with the 2nd highest mass/charge ratio
the peak with the highest is the M+1 peak caused by Carbon 13 isotope
6
Q
common fragments m/z value
CH3+
A
15
7
Q
common fragments m/z value
C2H5+
A
29
8
Q
common fragments m/z value
CH3CH2CH2+ OR CH3CHCH3+
A
43
9
Q
common fragments m/z value
OH+
A
17
10
Q
to identify compounds using MS
A
- identify fragments
2. piece together to form a molecule with correct mr
