1.Analysis Flashcards
Typesa of analysis?
- infrared spectrum
- mass spectro
- NMR
- chromatography
Spin and a magnetics field effect on it
spun in either of two directions normalls of same energy level
if you put the neuclues in amagnetic field then the spin directions have different energy (as oes field is witht he big field)
this energy difference can be picked up by firing em radion at it
what must neucli have for NMR
odd number of protons/neutrons
as the unpaired one will produce a residual magnetic field
NMR resonance
the enrergy difference between the two states
type of em radiation used in NMR
radio waves
what is chemical shift (little delta)
a scale that compares the frequency of an NMR absorbtion with the frequency of the reference peak of TMS
what is chemical shift measured in?
perts per million (ppm)
what is cmemical shift of C and H measured relative to?
TMS , or (CH3)4Si
whys is tms used?
chemically unreactive and volatile
as the C13 , H1 and (Si29) all only have one environment
(added in with the sample)
what is chemical shift effected by?
- electronegative atoms nearby
- pi bonds nearby
Higer value in table always wins
what solvents must be used for NMR?
deuterated solvents.
D is a H with another neutron
CDCl3 is used as the solvent
why is CDCl3 used as the solvent?
as the peak will always be in the same place so can be removesd, and hydrogen has no peak.
The solvent can be evaporated off to recover the sample
what can you get from carbon NMR?
- numbe rof environments
- type of environment
whatc can u tell from hydrogen NMR?
- number of environments
- type of environment
- proportion of hydroens in each environment
- adjacent protons
what is an integration trace
a line that increases in height as it passes each peak, shows the ratio in each peak.
what is spin spin coupling and what causes it
the splitting of peaks caused by the magnetic interaction of neibouring hydrogens either lined with or against the hydrogen.
(only between hydrogens of different environment)
SSC names
- Singlet
- Doublet
- Triplet
- Quartet
- multiplet
how to predict splitting pattern
n+1 rule ( in pattern of pascals triangle)
whats annoying about -OH and -NH NMR
the peaks will be over a very wide range of delta values
what does D2O do?
makes -OH and -NH hydrogen peaks disappear
as the H becomes a D
Do -OH and -NH peaks split?
nope
as the OH forms broad peaks as hydrogen bonding happens
NMR uses?
- medicine
- body scanning
what is partition cromatography?
- mobile phase is a liquid or gas
- stationary pahsae is a non volatile liquid
- distributed by solubility
what is adsorbtion chromatography?
- mobile phas eis a liquid or gas
- stationary pahse is solid
- they adsorb onto the solid surface
what is paper chromatography?
- partition types
- stationary phgase is water
- mobile is solvent
what is thin layer chroma
- adsorbtion type
- mobile phase is solvent
- stationary is the surfact of SiO2/Al2O3 on inert glass sheet
what id Rf
distance travelled by compound/distance by solvent
how does a solid stationary pahse seperate?
by adsorbtion
how does a liquid stationary phase seperate?
by solubility
limitations of tlc
- similar compounds has similar Rf
- Unkowns have no Rf
- Hard to find a solvent that seperates all compounds in a mizture
gas liquid chromatography?
- stationary phase is a thin layer of solid/liquid
- mobile phase is a carrier gas. something unractive like helium
- you measure the time not the distance and get retention time
- Moves more if its more volatile and less soluble(/adsorbtion)
- partiion type
GLC setup
- 30m long inert capillary tubing
- inside a controlled oven
- usually feeds into mass spectrum after detection.
glc limitations?
- could have some retention time
- substances could avoid detection
- unknows have no known retention time
why is gas chromas , mass spectrum good?
cause the gas chroma will seperate the mixture
the mass spectrum will help identify it
uses for GS-MS
- forensics
- environmental analysis
- airport security
- space probes
Getting proportions freom GS
Use the relative peak areas
What is retention time
The time from the injection of the samplefor the compound to leave the column
