organic compound analysis Flashcards
m/z
mass-to-charge ratio
mass spectromery uses
calculate molecular weights of sample’s contents
identify unknown compounds and their physical structure
distinguish between isomers
stages in mass spectronmeter (instrument)
1) sample is vaporised
2) ionisation: bombarded w electrons -> framgents
3) deflection by magnetic field
4) detection
only positively chared particles are measured and compound must be (g)
how are compounds ionised in mass spectrometry (show an equation)
bombardment with electrons knock of an electron
eg X+ e- -> [X]+ + 2e-
(need to be able to show ionisation equation)
fragmentation
breaking of almost any bond in a molecular ion into a fragment and an alkyl group
eg M+ -> X+ (FRAGMENT) + R.
dot in R. represents unpaired electron. R. is not +vely charged
base peak
molecular ion peak
base= most abundent fragment
molecular/parent= highest Mr
IR spectroscopy function and principles
principle= use infrared radiation to vibrate covalent bonds making the bonds bend/stretch
function= info about covalent bonds, functional groups and structure/ type of molecule
possible uses of IR spec
- identify org compounds
- design new drug
- analyse proteins
- testing blood alcohol
relationship between bond strength and the absorption of IR radiaion
weaker bonds require a lower fq of radiation to vibrate bonds
bond that vibrates a higher fq adsorbs IR radiation with a higher wave#
relationship between mass and IR absorption
atoms with higher masses absorb lower frequency radiaion
how to tell IR with most amount of C-H bonds/ longest chain
more peaks in fingerprint region
NMR
Nuclear Magnetic Resonance spectroscopy => determine entire structure/ provides structural information
magnetic field interacts with nuclear spin of atoms
- short powerful radio pulse absorbed by nuclei -> flip to high nrg spin status
- spectrum produced when nuclei return to low nrg spin states releasing a pulse of nrg
fts of NMR
form of absorbance specroscopy
v fast
v expensive and hazardous bc of strong magnetic field
qualitative data
chemical shift
distance from standard peak (far right given by standard compound TMS= tetra methyl saline which has lowest known chemical shift=0)
why is the chemical shift different for different hydrogen environments
Because diffent hydrogen environments have different atoms surrounding its nucleus, this affects the amount of chemical shielding experienced thefore affecting the energy emitted from the nucleus spinning
area under peak
ratio of hydrogens in environment
splitting patern
number of hydrogens on neighbouring carbons (only H NMR)
number of peaks=
number of neighbouring H atoms (n) + 1
1 neighbouring = doublet ect
chromarography
technique to separate substances in a mixture
- stationary phase
- mobile phase
Sample _ _ to the stationary phase
and _ _ to the mobile phase
adsorbs and desorbs
which molecules are more attracted to the polar stationary phase
polar molecules
stationary phase
solid onto which compounds of a sample adsorb
mobile phase
phase that flows through stationary phase carrying components of a sample with it
adsoption
desorpion
ad= components adhere to the stationary phase
de= component released from the stationary phase and dissolves into mobile phase
