Spectowcopy Flashcards
Infrared spectroscopy
All bonds vibrate at a characteristic frequency
Different types of vibration
The frequency depends on the mass of atoms in the bond the bond strength and the type of vibration
The frequencies at which they vibrate are in the infrared region of the electromagnetic spectrum
Ir light passing through a compound
Absorb some or all of the light as the frequencies at which the bonds vibrate
Wave numbers are used as a measure of the wavelength or frequency of the absorption
If ir is absorbed then the range is 4000-400
Above 1500 is used to identify functional groups
Below 1500 is used for fingerprinting
Wave number =
1/wavelength
Finger printing
Complicated and contains many signals
Picking out functional groups signals are difficult
This part of the spectrum is unique for every compound and so can be used as a fingerprint
This region can also be used to check if a compound is pure
Oh peaks
Broad and fat (nethra)
R and s have oh binds
T has c=o
R & S (unique) fingerprint region or below 1500 cm
Compare to a database / known spectra
Why is radiation from the sun not absorbed in the atmosphere
The radiation isn’t at the right frequency to be absorbed
Why does earth emit lower energy infra red
It absorbs some of the energy so the red is uneffected
What happens when molecules abroseb Indra red emitted by the earth
They vibrate more vigorously
Greater kinetic energy transferred to neighbouring molecules becomes thermal thermal energy
Which gases are potent greenhouse gases
Ch4
H20
Co2
Is a greenhouse effect undesirable for earth
-keeps earth warm @ night + cold during the day
-Deseriable
-enhanced greenhouse effect isn’t good
Haloalkane to alkane
Elimination
Haloalkane to anytHing else
Nucleophillic substitution
Alkene to anything
Elctronillic addition is in the name
