Infrared Spectroscopy
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What are the bonds between atoms in a molecule able to do?
stretch and bend, absorbing infrared energy and creating the infrared spectrum.
What does absorption of infrared radiation cause?
changes in the vibrations of a molecule (bending and stretching of bonds)
What is IR sperctrocopy used in?
structure determination
What do groups of atoms in a molecule give rise to?
characteristic absorption bands in the IR spectrum
What does the interpretation of an IR spectrum, and identification of the compound responsible require?
the uses of correlation tables of infrared data
What is the spectral region in IR?
400 to 4000 cm-1
When are stretching vibrations most useful?
when assigning peaks to specific bonds
If a carbonyl group is present, where will there be a strong absorption?
around 1750 cm-1
If a carbonyl group is present what 4 types of compounds are possible?
Acids Esters Aldehydes Ketones
If the compound is an acid, what should you look for and why?
Look for a broad absorption near 3400 cm-1 due to H- bonding between O-H groups
If the compound is an ester, what should you look for?
Look for C-O stretch near 1200cm-1
If the compunds is an aldehyde/ketone, what should you look for?
Look for C-H stretch just below 3000 cm-1
If the compound is an alcohol, what should you look for?
Look for O-H stretch near 3300 cm-1
What does aliphatic mean?
straight chain/ non-aromatic