Chapter 29: Chromatography and Spectroscopy Flashcards
(21 cards)
Adsorption
Solid silica can hold different mixtures on its surface
What are the two phases?
Stationary
Mobile
What are the key features of TLC
quick and inexpensive
What is the stationary phase in TLC
adsorbent substance (silica)
What is the mobile phase in TLC
solvent
Key features of gas chromatography
Separate volatile organic compounds
What is the stationary phase in gas chromatography
High boiling point liquid adsorbed onto inert solid support
What is the mobile phase in gas chromatography
Inert carrier gas which carries components through capillary columns
Retention time
Time taken for each component to travel through a column
How do you determine concentration from peak integration?
1) Prepare standard solution of known concentration
2) Obtain gas chromatograms for each standard solution
3) plot calibration curve of peak integration against concentration using external calibration
4) obtain gas chromatogram for the compound being investigated under the same conditions
5) use calibration curve to measure concentration
How do you identify OH and NH proton environments?
Proton exchange
Deuterium exchanges and replaced OH and NH
Second spectrum run on CH3OD
Since deuterium does not absorb in this chemical range, OH peak disappears
Resonance
Electrons have two different spin states they alternate between when absorbing energy from strong magnetic fields and radio frequency
TMS
Standard reference chemical for which all chemical shifts are measured
Deuterated solvent
Solvent used in NMR since it produces no signal
CDCl3
How do you test for alkenes?
add bromine water drop-wise
How do you test for haloalkanes?
Add silver nitrate and ethanol and warm to 50º in water bath
How do you test for carbonyls?
2,4 DNP
orange precipitate
How do you test for aldehydes?
Tollens Reagent and warm
silver mirror precipitate
How do you test for 1º and 2º alcohols and aldehydes
acidified potassium dichromate and warm in a water bath
orange to green
How do you test for carboxylic acids?
add aqueous sodium carbonate
How do you test for phenols?
Reaction with bromine at RTP
white precipitate formed as bromine decolourises
