analysis Flashcards
molecular ion
formed when compound is placed in mass spectrometer and loses an electron to form positive ion
fragmentation
molecular ions break down into smaller pieces- fragments in the MS
M+1 peak
exists because 1.1% of carbon is present as the carbon-13 isotope
factors for bond stretching
mass of atoms in bond
strength of bond
can absorb IR radiation
Infrared spectroscopy
used to identify functional groups present in organic molecules
IS method
sample placed inside IR spectrometer
beam of radiation passed through molecule
molecule absorbs some frequencies and emerging beam is analysed
IRS connected to computer that plots graph
fingerprint regvion
contains unique peaks which can be used to identify molecule
applications of IRS
identifying pollutants from vehicles
IR-based breathalysers detect ethanol in the breath
identifying phenol
use pH indicator paper
not as acidic as COOHs- do not react with sodium carbonate
undergoes electrophilic substitution with bromine at room temp- bromine is decolorised and white precipitate formed
stationary phase TLC
thin metal sheet coated in Al2O3 or SiO2
solute molecules absorbed
more the molecules interact with the stationary phase, the more they will ‘stick’ to it
mobile phase TLC
flows over stationary phase
liquid solvent carried components fo the compound being investigated
polar solvents- water/alcohol
non- polar solvents- alkanes
locating spots TLC
could be seen if the sample components are coloured
if not: use UV light / ninhydrin/ iodine vapour
TLC method
prepare beaker with small quantity of solvent
draw horizontal pencil line at bottom edge of TLC plate
place spot of pure reference left and sample on right - allow to air dry
place TLC plate in beaker- solvent no higher than baseline
allow it to travel and then analyse result
Rf value
distance travelled by component/ distance travelled by solvent
used to deduce composition of mixtures
