Lecture 5

Question 1

spectroscopy

Answer 1

• interaction between matter and electromagnetic spectrum
• effect of radiation on a molecule changes with the wavelength (energy) of light
• IR determines the functional group
• help measure energy needed to vibrate the bonds, move them and their chemical nature

Question 1

functional group

Answer 1

part of the molecule with distinctive chemical groups/properties
same functional group = same chemical properties

Question 2

bond vibration

Answer 2

adding energy compresses a bond
repulsion will push them apart
happens with bond vibrations

Question 3

quantum mechanics

Answer 3

tiny bonds are governed by quantum mechanics
for permitted bonds, only some vibrational energies are permitted

Question 4

how to add energy to push the bonds together?

Answer 4

bonds need to vibrate
shine some light (corresponds to wavelength of infrared)
causes vibration because light = energy

Question 5

energy equation

Answer 5

E = hc/ wavelength = hv
as energy increases, wavelength decreases
deeper the well, stronger the bond

Question 6

IR

Answer 6

each molecule has a different arrangement of bonds
IR shows what functional groups are present
non-destructive
light can penetrate through glass or plastic

Question 7

IR spectroscopy

Answer 7

lots of incoming light, lots of different energies
some energies pass through (transmitted), others cause bond vibrations
exact energy tells us the strength of the bonds

Question 8

wavenumbers

Answer 8

check notes

Question 9

dipole moment

Answer 9

when IR light is shone at a sample, it will only be absorbed if:
- the energy of the radiation corresponds to the energy
- lead to a change in the dipole moment of the bond

Question 10

dipole

Answer 10

separation of charges
unequal sharing or distribution of electron between atoms