L31- UV AND IR Spectroscopy Flashcards
1
Q
How does UV spectroscopy work?
A
- UV is shone on a molecule
- radiation between 200-700 wavelength
- electrons in the bonds get excited and vibrate
- some of the energy is absorbed as it passes through
- the more loosely held electrons within the bonds absorb the longest wavelength radiation.
2
Q
what type of molecules are UV active?
A
- molecules that have conjugation in them, due to loosely held electrons in conjugated system.
- atoms that have lone pair of electrons, due to loosely held electrons
- aromatic rings, delocalised electrons
3
Q
why does protonation affect UV active?
A
protonation affects molecules as it means it REDUCES the availability of the lone pair of electrons
4
Q
What are the different types of vibrating in IR spec?
A
- stretching
- deformation
- combinant overtones
5
Q
what does a molecule have to be to be IR active?
A
there needs to be a dipole moment present eg. C-O
6
Q
What is the frequency of O-H
A
3400
7
Q
What is the frequency of N-H
A
3400
8
Q
What is the frequency of C-H
A
3000
9
Q
What is the frequency of C=O
A
1715
10
Q
What is the frequency of C=C
A
1650
11
Q
What is the frequency of C-O
A
1100
