4.2.4 Analytical techniques Flashcards
what happens to the bonds in a molecule when infrared radiation is absorbed
covalent bonds vibrate
on an IR spec what is seen above 1500cm-1
functional group identification
on an IR spec what is seen below 1500cm-1
fingerprinting
how can you tell the difference between a peak for an alcohol and a peak for a carboxylic acid on an IR spec
carboxylic acid’s peak is very broad
examples of greenhouse gases
carbon dioxide
methane
water vapour
what is the main greenhouse gas in the atmosphere
water vapour but it is natural
what do greenhouse gases do
trap the Earth’s radiated infra red energy in the atmosphere
what is infrared radiation absorbed by
C=O
O-H
C-H
in carbon dioxide, water vapour and methane
these absorptions contribute to global warming
what is the greenhouse effect of a gas dependent on
atmospheric concentration
ability to absorb infrared radiation
residence time (time in atmosphere)
How have levels of carbon dioxide in the atmosphere increased
Burning of fossil fuels
What do modern breathlysers do
Measure ethanol
Using IR spectroscopy
What can IR spectroscopy
Monitor gases causing air pollution (CO and NO from car emissions)
Breathalysers
What is the molecular ion
Peak with largest m/z
Due to complete molecule
Equal to Mr of molecule
Called parent ion
Fragmentation
When organic molecules are passed through a mass spectrometer
Detects whole molecule and fragments of the molecule
Forming molecular ion
M -> [M]+• +e-
Molecule loses an electron and becomes both an ion and a free radical
Ion is responsible for peak
