Analytical Techniques 4.2.4 Flashcards
What is Infra-red Spectroscopy?
When IR is shined at an organic sample and the frequency of wave that pases through it is recorded
Why do some Frequencies get absorbed?
Because their energy is transfered to the bond, causing a greater amplitude of bond stretching
What is Bond Stretching?
When two atoms vibrate about their joining bond as covelant bonds aren’t rigid.
What does an IR spectrum graph look like?
% transmitance on Y axis
Hz on X axis
Most of the line sits at 100%, dips down at bonds as less IR is transmitted
What bonds should be ignored on an IR Spectrum?
C-H bonds 2850–3100cm^-1
As they are in just about all organic molecules
What are uses of IR Spectroscopy?
Breathalyzers
Monitoring Air Pollution
What is a Mass Spectrometer
A device used to determine the mass of the organic molecule and thus what it is
How does a Mass Spectrometer work?
1) A beam of high energy electrons bombard the sample, Ionising the sample (forming positive ions as wave/particle).
2) Ions are accelerated through a B-field. Causing heavier molecules to not curve as much.
3) A detector works out the mass of the molecule colliding with it due to its position.
What is the most important peak in a Organic Mass Spectrum?
The furthest right as this is the Molecular Ion.
Which is the ionised version of the molecules, so has the same mass.
What can Mass Spectroscopy be used for?
Determining the relative abundance of Isotopes.
Identifying mass of Organic compound (thus their composition)
How are Mass Spectrums used to identify the abundance of Isotopes?
The heavier isotopes are deflected less by the B-field.
What are the other peaks in an Organic Mass Spectrum?
Fragments of the Compound
eg. a peak at 15 would be CH3+ which can be broken from most organic compounds.
Or a peak at 17 which would be OH+
