Infra Red Spectroscopy Flashcards
What will the infra red do
Raise the energy of molecular vibrations by 1 energy level (these are quantised which we know because of the harmonic oscillator quantisation)
Conditions for IR spectroscopy
Photon must have the correct frequency to raise the vibration by 1 energy level.
Also, the molecule must have a changing dipole moment
What is a changing dipole moment
When the position of the dipole (net charge) changes
Condition for IR spectroscopy mathematical
dμ/dr ≠0
Where r is distance between the molecule and μ is the dipole moment
Dipole moment equation
μ =qr, q is charge
What type of vibration for CO2 will not vibrate
Symmetric stretch as no change in dipole
What makes studying the spectrum of large polyatomic molecules easier
If they have normal modes which can be identified
What is a normal mode
Vibration that can be excited without exciting any other bonds
What are normal modes usually
Functional groups
What are the axes of a IR spectrum
y axis will be quantity absorbed.
x axis will be wavenumber
Why must the molecule have a changing dipole moment in order to be suitable IR spectroscopy
Since light has an alternating charge since it is electronegative in order for it to interact with the molecule, the molecule must have a changing dipole.
