Download Analytical chemistry 2

Analytical chemistry 2
Mass spec cont.
IR absorption spec
Mass spec starter
1. What are the 4 main stages of mass spec?
1.
2.
3.
4.
Ionisation
Acceleration
Deflection
Detection
Mass spec for ethanol - interpret
2. Base peak
3.
4.
1. M+
5.
Infrared Spectroscopy
•Visible light is made up of a continuous range of
different electromagnetic frequencies.....so is Infrared
radiation (the eye just can’t see it)
•Each frequency of light (including infra-red) has a
certain energy.
How IR spectroscopy works…
•Shine a range of IR frequencies, one at a time
through a sample of organic compound and at
some of the frequencies the energy will be
absorbed.
•A detector on the other side of the sample
would show that some frequencies are
absorbed whilst others are not.
• If a particular frequency is being absorbed as
it passes through the compound being
investigated, it must mean that its energy is
being transferred to the compound.
• Energies in infra-red radiation correspond to
the energies involved in bond vibrations.
Bend and Stretch
• In covalent bonds, atoms aren't joined by rigid
links;
• the two atoms are held together because both
nuclei are attracted to the same pair of
electrons.
• The two nuclei can vibrate backwards and
forwards - towards and away from each other
- around an average position.
All molecules absorb infrared radiation;
absorbing energy makes the bonds vibrate.
STRETCHING
BENDING
Every bond vibrates at its own frequency, dependant upon bond
strength, bond length and the mass of atoms involved in bond.
Fingerprint regions
• You must be able to identify the following
peaks.
– C-H in alkanes/alkenes/aldehydes
– O-H in alcohols/carboxylic acids
– N-H in amines
– C=O in aldehydes and ketones
– C-X in halogenoalkanes
Which functional groups are present in this spectrum?
Which functional groups are present in this spectrum?
Which functional groups are present in this spectrum?