Analytical Techniques Flashcards
What is M+, what does the M+ peak tell us and where is it found?
Molecular ion, tells you the Mr, found on the far right of the spectrum
What is fragmentation?
Process that causes a positive ion to split into pieces, one of which is a positive fragment ion
What are the 3 greenhouse gases?
Water vapour, CO2 and methane
How do the greenhouse gases cause global warming?
Absorb infrared radiation and re-emit this energy as radiation which increases the temp. of the atmosphere
Below which wavenumber in infrared spectroscopy should peaks be ignored?
1500cm-1
What shape and wavenumber is a C-H bond peak?
Sharp and strong, around 3000cm-1
What shape and wavenumber is an O-H bond peak (alcohols)?
Smooth and broad, 3200-3600cm-1
What shape and wavenumber is a C=O bond peak (aldehydes, ketones and esters)?
Sharp, strong and narrow, 1630-1820cm-1
What shape and wavenumber is an O-H bond peak (carboxylic acids)?
Smooth and broad, 2500-3300cm-1 (will also have a C=O bond peak if carboxylic acid)
What is the method for TLC (6 steps)?
- Dissolve sample in solvent
- Draw base line in pencil on silica plate 1cm from the bottom
- Spot samples on base line, evenly spread
- Place plate in beaker of solvent with solvent depth of 0.5cm, put lid on beaker
- Remove plate when solvent front is near the top, mark solvent front position
- Calculate Rf of each spot, compare to a database
What is the stationary phase in thin layer chromatography (TLC)?
Silica plate
What is the mobile phase in thin layer chromatography (TLC)?
Solvent
How does separation occur in thin layer chromatography (TLC)?
Relative ADsorption (attraction)
How is the Rf value calculated?
distance travelled by dot / distance travelled by solvent
What are the 2 limitations to Rf values?
- Similar compounds can have similar Rf values
- Unknown compounds have no reference Rf for comparison
