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SAFETY: Acetylsalicyclic acid (aspirin) is an irritant.
IR Table.pdf
Aspirin is commonly used as aspirin, an over-the-counter analgesic!
Predict the IR spectrum of aspirin
Predict the IR spectrum of aspirin
1. Make a list of each functional group in aspirin
For every double bond, indicate whether it's conjugated or saturated
2. Go to the IR Table of Values (keep this open in a separate tab)
Find each functional group, corresponding bonds, and expected wavenumber ranges.
Include notes about peak shape: broad, strong, medium, weak
The substitution pattern of the benzene ring matters!
Notice the C-H bend region is large, go to Table 2 of the reference table to get a closer approximation of bending frequency based on substitution pattern of the benzene ring
Enter this information into a table, format below.
Interpret the literature IR spectrum of aspirin:
Interpret the literature IR spectrum of aspirin:
Follow the "expected wavenumber range" in your table, look for a signal that corresponds to each.
Enter the corresponding wavenumber from the spectrum below in the literature column of the aspirin table
Some signals may not be labeled and some signals may overlap with others
It is not necessary to assign every signal indicated in the spectrum to a bond
Literature IR
Literature IR
ASP.mp4Preparing the sample
Preparing the sample
Solid samples are ground in a mortat & pestle with nujol (alkane mixture) to make a mixture (like thin toothpaste) that is transferred to the plate
Interpret the observed IR spectrum of aspirin:
Interpret the observed IR spectrum of aspirin:
Follow the "expected wavenumber range" in your table, look for a signal that corresponds to each.
Enter the corresponding wavenumber from the spectrum below in the observed column of the aspirin table
Some signals may not be labeled and some signals may overlap with others
It is not necessary to assign every signal indicated in the spectrum to a bond
ASP_IR.mp4Measuring the IR spectrum
Measuring the IR spectrum
Observed IR
Observed IR
Common mistakes: adding too much sample to the NaCl plates.
Click the button on the right to see what NOT to do before analyzing carvone and aspirin.
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