Analytical techniques
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How does IR spectroscopy works
Infrared radiation cause covalent bond to vibrate more and absorb energy
What are the axes for Infrared spectrum
Y axis: transmittance (%) X axis: Wavenumber (cm^-1)
What is the fingerprint region
Below 1500cm^-1 when there are lot sof peaks
How to identify the compound in fingerprint region
Using a database
What 3 part of information should be included when analysing IR spectrum
• The type of bond present • The wavenumber • The functional group it’s in
Why do we ignore peaks at 2850- 3100
As it’s the C-H bond and all organic compound have C-H
How to identify C=C
Peaks at 1620 -1680
How to identify C=O
Peak at 1630 - 1820
How to ideantify C≡N
Peak at 2220 -2260
How to identify O-H acid
Broad peak at around 2500-3300 ( mixed with C-H peaks )
How to identify N-H
double peaks at 3300- 3500
How to identify O-H alcohol
Peak around 3200-3600 ( To the left of C-H peaks )
Why may there be a small stretch at the range of alcohol
Due to water impurities
What are the 3 green house gases
• Water vapour • Carbon dioxide • Methane
Why do the greenhouse gases vibrate more
They absorbed infrared radiation
Why do the gases lead to global warming
They re-radiate some gases back to earth
What makes the most effective greenhouse gas
To absorb the most infrared radiation , they will vibrate most
What is the most effective green house gas
Water vapour
What is infrared spectroscpoy used for
• Monitor air pollution • used in modern breathalysers
How does infrared monitor vehicle emission
Sensors detect and measure quality of pollutants E.g. CO, NO
How is infrared used in breathalysers
Ray of IR is passed through breath, bond of ETHANOL are detected and measured.
What is electron impact ionisation
When molecule lose an ion and form a molcular ion. (by hitting by a high energy electron)
What is fragmentation
when the molecule/fragments break up and give a series of peaks
What is the highest m/z ratio peak
the complete molecular ion