IMFs and Symmetry
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What are the five different operations involving symmetry?
Identity Rotations Reflections Inversion Improper rotations
What letters are used for rotations?
C and D
When do we use D to talk about rotations?
When there are perpendicular rotations to the rotation axis of the highest order.
What letters do we use to discuss reflections?
v and h
When do we use h to talk about reflections?
We use h to talk about the reflections perpendicular to the v-axis.
What are the 6 types of vibrational modes?
Symmetrical, Scissoring, Wagging Asymmetrical, Rocking, Twisting
What is the equation for the number of vibrational modes for a linear molecule?
3N-5
What is the equation for the number of vibrational modes for a nonlinear molecule?
3N-6
What does N represent in the equation for vibrational modes?
N=# of atoms in the molecule
Describe IR
IR utilizes transmittance and relies on the presence of a dipole. (Dipole=Asymmetry)
Describe Raman
Raman utilizes excitation and emission and relies on scattering.
Is it possible to see nonpolar molecules in a Raman spectra?
Yes
What does d stand for when we talk about mirror planes in a molecule?
The diagonal mirror planes along the highest order axis that is vertical
What does S stand for in the various symmetry operations?
Improper rotations
What operation must always exist when considering symmetry?
Identity (E)