Spectroscopic Techniques
HNMR
Mass Spectroscopy
Infrared Spectroscopy
Relative to the spectrum produced by the hydrogen nuclei in tetramethylsilane
Fragmentation pattern is produced
Allows us to identify absorption peaks in specific regions due to their bonds.
The fingerprint region is below 1500cm
Inside the mass spectrometer, some of the molecular ions break down to produce fragments.
Allows you to see the different masses of an element when they are ionised.
You can identify functional groups above 1500cm^-1according to their signal
Different peaks are distinctive in terms of intensity and wavenumber.
Sorting them out according to their M/Z ratios
Stages of Mass Spectroscopy
Ionisation
Acceleration and deflection
Hydrogen nuclei found in different chemical environments, the peaks on an HNMR spectrum represent each environment.
Vaporisation
Detection
If there is a C-O bond you are expected to see a peak around 1000-1300cm^-1
If there is a O-H bond you are expected to see a peak at around 3200-3600 cm^-1
Able to identify a molecule
The number of proton (hydrogen) environments
The type of protons (e.g. -OH, -CH3 by the chemical shift
The integration - how many protons there are of each type
How many protons are next to each other by analysing the spin-spin coupling
which gives useful information about the structure of the compound.
The ions are accelerated so that they all have the same kinetic energy and are deflected from a electromagnet. Light ions are deflected the most
The molecuels are being ionised knocking one or more electrons off. Ionisation results in the formation of a molecular ion (M+).
Ions pass through a beam that detects the ions.
When identifying the hydrogen environments in a compound. One must consider the symmetry of the compound.
the number of peaks = the number of hydrogen atoms on the adjacent carbon +1.
HL
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Singlet- next to no other hydrogens
Doublet- next to 1 other hydrogen
The number of peaks gives the number of different chemical environments in which the hydrogen atoms are located.
Triplet- next to 2 other hydrogens
The molecule will only break into two fragments.
Each hydrogen molecule / type of proton has a specific chemical shift which can allow you to identify it on a graph
The shape and intensity of the peak helps to identify the functional groups
The fingerprint region is more complicated to read as it contains alot of peaks.
Quartet- next to 3 other hydrogens
If IR light is passed through a compound, it will absorb some of/all of the light at the frequencies at which its bond vibrate.
The height of the splitting patterns/peaks follow Pascale Triangle
Quintet- next to 4 other hydrogens
Single peaks in low resolution can correlate to multiple peaks at a high resolution