4.17 Spectroscopy ✓
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1
What is a molecular ion?
positive ion formed when organic compound placed in mass spectrometer loses an electron 
2
What does a mass spectrometer detect?
mass-to-charge ratio of molecukar ion which gives molecular mass of compound
3
What is the molecular ion peak?
clear peak at highest m/z value on right of mass spectrum
4
What is the M+ 1 peak?
very small peak one unit after M+ peak
5
What causes M+1 peak?
1.1% carbon present as carbon-13 isotope
6
What is fragmentation?
process of molecular ions breaking down into smaller pieces known as fragments
7
What are other peaks in a mass spectrum caused by?
fragment ions formed from breakdown of molecular ion
8
What does the simplest fragmentation break into?
positively charged fragment ion + radical
9
Are uncharged radicals detected by mass spectrometer?
no
10
Are positive ions detected by mass spectrometer?
yes
11
How can you identify 2 molecules with the same molecular mass and molecular ion peak using spectroscopy?
fragment ions found in spectrum may be different
12
What happens to bonds when they absorb ir?
bend or stretch more
13
Describe stretch vibration in bonds
movement along line between atoms 
14
Describe bend vibrations in bonds
change in bond angle
15
What does the amount a bond stretches or bends depend on?
-mass of atoms (heavier vibrate slower)
-strength of bond (stronger vibrate faster)
-strength of bond (stronger vibrate faster)
16
Can bonds only absorb radiation at the same frequency as the natural frequency of the bond?
yes
17
What is the wavenumber?
scale proportional to frequency of wave
18
How does ir affect global warming?
-ir radiation passes through atmosphere to earth where most is absorbed
-some is re-emitted in longer-wavelengths which is absorbed by greenhouse gases due to it matching their natural frequency
-this increases global temperatures
-some is re-emitted in longer-wavelengths which is absorbed by greenhouse gases due to it matching their natural frequency
-this increases global temperatures
19
How is ir radiation used to monitor pollution?
remote senors detect and measure vehicle emmisioms like CO, CO2 and hydrocarbons in an area
20
How is ir radiation used in breathalysers?
analyses ir absorbance in breath, ethanol bonds can be detected and the more the absorbance, the higher the reading and the more ethanol
21
What are the steps for identifying a molecule?
1. elemental analysis: determine empirical formula using percentage composition
2. mass spectrometry: determine molecular mass and sections of a molecule
3. infrared spectroscopy: identify bonds and functional groups
2. mass spectrometry: determine molecular mass and sections of a molecule
3. infrared spectroscopy: identify bonds and functional groups