Spectroscopy Flashcards
What is nmr spectroscopy
Interaction of low energy radio waves and nuclei within a strong magnetic field
Types of nmr
Carbon 13
H (proton)
Carbon 13 nmr
Peak for every different carbon environment ( equivalent c atom)
H nmr
A peak for each set of hydrogen environments
Integration ratio
Each signal is proportional to the number of equivalent H atoms
Spin spin coupling
High resolution h nmr each signal can be split into further lines depending on neighbouring carbon atoms
Splitting of peak
Number of inequivalent Hs on neighbouring c atoms + 1
NMR solvents
CDCl3
D2O identify oh and amide
Calibration compound
Tetramethylsilane added to calibrate the spectrum
1 NMR peak at 0
Inert and volatile doesn’t react
Why is TMS used
Signal is away from all the others
Only gives one strong signal
Non toxic
Inert
Low bo so can be removed easily
Electronegativity effect on nmr
The more electronegative an atom bonded to a carbon the greater the ppm
What is chromatography
Analytical tech that separates components in a mixture between a mobile phase and stationary phase
How does a solid stationary phase separate
Adsorption
How does liquid stationary phase separate
Relative solubility
TLC paper
Contains silica which is very polar
If stationary phase was polar and mobile stage was non polar what would happen to the compounds
If compounds were non polar they would pass through the column quicker than the polar molecules as non polar molecules are more soluble in the mobile phase
Gas liquid chromatography
Used to separate mixtures of volatile liquids due to different adsorption and attraction to the different phases
Retention time
The time taken for compound to travel from injection to where it leaves the column to the detector
Slower the retention time
Greater attraction to the stationary phase more adsorption therefore takes longer to travel out of the column
