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1. Preparing a solid sample
1. Preparing a solid sample
using Nujol (mulling agent)
2. Adding mull to IR plates
2. Adding mull to IR plates
there should be limited light scattering!
Before analyzing IR spectra:
Make a list of unique functional groups (FG) for each molecule
For double bonds, identify whether it's conjugated or saturated
Go to the IR table of values (below)
Find each FG, list corresponding bonds and expected wavenumber ranges
Include notes about peak shape: broad, strong, medium, weak
Enter this information into table format
scroll within window to stay on this page or click on link to bring up IR table in a new window....
IR Table.pdf
background.mp4Before measuring the IR spectra of samples:
Before measuring the IR spectra of samples:
Collect a background spectrum:
The IR spectrum is usually displayed as percent transmittance (%T) – how much of the original IR intensity is left after passing through the sample
In order to precisely measure this, we first need to know the IR intensity with no sample in the pathlength, so we run a background spectrum
Discuss:
If no sample is in the spectrometer during the background scan, what is around to absorb IR light? (hint: there are IR peaks near 3800 and 1600 cm-1)
Results: IR spectra (observed wavenumbers):
Results: IR spectra (observed wavenumbers):
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