Spectroscopy Flashcards
What happens to a compound when it is placed within the mass spectrometer?
It loses an electron and becomes the molecular ion
What does a mass spectrometer detect?
The mass to charge ratio (m/z) which gives us the molecular mass of the compound.
What do we look for in a mass spectrum in order to find the molecular mass?
We look for the molecular ion peak. This is the highest peak in m/z which is the furthest to the right.
Why is there a small peak right after the molecular ion peak?
Because 1.1% of all carbon is actually carbon-13, some compounds contain extra mass because it contains the isotope and not the more common carbon-12.
What is fragmentation in mass spectrometry?
Where the molecular ion breaks down into multiple smaller pieces. These fragments form the other smaller peaks found in mass spectrums.
Why do different molecules with the same mass have different mass spectrums?
The different molecules will fragment differently so the fragment peaks will be at different places.
How does absorbing Infrared Radiation (IR) affect bonds?
IR will make the bonds stretch and bend more
When can bonds only absorb radiation?
When the frequency of the radiation matches the natural frequency of the bond.
How does mass affect bond vibration?
Heavier atoms vibrate more slowly than lighter ones.
How does strength affect bond vibration?
Stronger bonds vibrate faster than weaker bonds.
What does infrared spectroscopy try to identify?
The infrared spectrometer is supposed to identify functional groups in organic molecules.
What does a peak indicating an alcohol look like?
A medium peak between 3200-3600cm⁻¹ caused by the O-H bond.
What does a peak indicating an aldehyde or ketone look like?
A very think peak between 1630-1820cm⁻¹ caused by the C=O bond.
What does a peak indicating a carboxylic acid look like?
A large peak between 2500-3330cm⁻¹ caused by the O-H bond. There is also a very think peak between 1630-1820cm⁻¹ caused by the C=O bond.
What is the fingerprint region?
An area of the spectroscope under 1500cm⁻¹ with unique peaks that can be used to identify a particular molecule.
