IR spectra exercises
Below is a table of some typical covalent bonds and their characteristic wavenumber at which energy is absorbed.
Bond
type |
Type
of molecule found in. |
Wavenumber |
C-O |
Alcohols
and esters |
1000-1300 |
C=O |
Carboxylic
acids and esters |
1680-1750 |
C=C |
Alkenes |
1600-1700 |
C-H |
Alkanes |
2850-3100 |
C-H |
Alkenes |
3000-3100 |
O-H |
Carboxylic
acids |
2500-3300 |
O-H
|
Alcohols |
3200-3600 |
Consider the IR spectrum on the right. Taking the wavenumbers above into account, discuss if this spectrum belongs to an alcohol or a carboxylic acid.
Should the trough at 3400 or 2950 be used to determine if the compound is an alcohol or an acid? Discuss.
Two bottles, one containing ethanol and the other containing ethanoic acid, were found on the table next to the IR spectrum shown on the right.
Which compound would form such a spectrum? Discuss.
