Chapter 29 Keywords Flashcards
Stationary phase
Doesn’t move and it is normally a solid or a liquid supported on a solid
Mobile phase
This moves, and is usually a liquid or a gas
Adsorption
The process by which the solid silica holds the different substances in the mixture to its surface.
Retention time
The time taken for each component to travel through the column
The compound is detected first has
- isn’t very soluble in the liquid stationary phase
- been retained in the column for the shortest time
- has the lowest retention time
Peak intergrations
The areas underneath the peaks that help you determine the concentration of the components in the sample
Neutrons
Number of protons and neutrons
Resonance
When the nucleus absorbs energy and rapidly flips between the two spin states
The frequency required for resonance is proportional to magnetic field strength
- this small quantity of energy can only be detected in strong uniform magnetic fields
- usually very strong super conducting electromagnet is used cools to 4K by liquid helium
Deuterated solvent
Solvent in which H atoms are replaced deuterium
Deuterium makes no NMR signal in the frequencies used in proton and carbon 13 NMR
Use CDCl3 as the solvent. But it still makes a peak for carbon 13 NMR, computer normally filters this out
Chemical shift
The shift in frequency compared to TMS required for a nucleus to undergo NMR. The shift depends on chemical environment, especially if caused by the proximity of e neg atoms or pi bonds
Integration trace
The area under the peak that the NMR spectrometer measures
*normally an extra line on the trace or a printed number next to the peak area
Eg. If the integration ratio was 2:3 then you have 2 protons in CH2 and 3 protons in a CH3
Spinning patterns
Subpeaks caused by the protons spin interacting with the spin states of nearby protons that are in different environments providing a lot of information about adjacent protons
Splitting patters follow Pascal’s triangle
Spin spin coupling/spin spin splitting
The splitting of a main peak into subpeaks.
Use the n+1 rule.
So if you had a proton next to n=5 immediately adjacent protons on s different carbon, the splitting pattern is n+1 so 5+1 which is sextuplet.
Singlet
Next to no hydrogens
1
Doublet
Next to a CH
1:1
Triplet
Next to a CH2
1:2:1
