organic analysis Flashcards
mass spectrometry
- analysis tool to identify unknown samples using unique mass spectrum
-measures mass to charge ratio (m/z)
mass spectrometer - instrumentation
ionises, accelerate, deflects and detects an atom or molecules so that mass to charge ratio is measured
- produces positive charged fragment
base peak
highest peak - largest absorbance and intensity
molecular ion peak
shows the molar mass of compound / highest m/z
why is there a small peak after molecular ion peak
an isotope (often carbon)
fragmentation
M+ -> X+ +R.
region of electromagnetic spectrum used in IR
infrared
region of electromagnetic spectrum used in NMR
radio waves
principles of spectroscopy
atoms/ molecules absorb and emit electromagnetic radiation of specific energies
purpose of IR
information about covalent bonds and functional groups present in organic molecule - identify structure and type of molecule
features of IR
expensive
fast
absorption spectroscopy
uses of IR
- identify of organic compounds
-design new drugs
-tests for blood alcohol
IR spectrum analysis
- specific covalent bond represents each peak
- a bond that vibrates at higher frequency absorbs IR radiation with higher wavenumber and greater energy bond
-must specify the O-H bonds but not as necessary for other types
NMR
-operates in radio waves
-form of absorption spectroscopy
-very fast and very expensive
- qualitative - structure of compound
principles of nuclear spin and NMR
- in order to interact with radio waves atoms must have nuclear spin
- in presence of external magnetic field nuclei line up in unstable arrangement
- normally in low energy state and aligned with strong magnet
NMR
ANALYSES THE H OR C ENVIRONMENTS
chromatography
- technique used ti seperate substances present in a mixture
- can detect the presence of a particular substance/ structure and concentration
common uses of HPLC
-COVID tests and pregnancy
- drugs present in blood
how chromatography works
- each substance analyses the different rates they move along the stationary phase depending on strength and solubility of mobile phase
-absorption to sp and desorption into mobile phase
stationary phases
polar sp - polar molecules
non polar sp - non polar molecules
- stronger adsorption tosp. = longer Rt
mobile phase
polar molecules - polar solvents vise versa
higher solubility in mobile phase= shorter Rt
talking about which sample is most strongly adsorbed to sp
-______ strongly adsorbed at sp and more readily desorbs to mobile phase
- moved least distance through column and leave later (longest Rt)
HPLC analysis
measure larger organic compounds and molecules as opposed to small volaile (gas)
measurements HPLC
- measures Rt- deduce compounds present SAME /IDENTICAL CONDITIONS -peak area( concentration)
Retention time
amount of time sample stays in column
- identifies a compound
- longer the Rt = adsorb more strongly and bigger
factors influencing Rt
- composition of sp and mp - increase SA
- length of column
-temperature and increase flow rate/pressure
reliability - interp. vs extrap
within range = interpolation
outside range = extrapolation
primary standards
pure substances whose mol/ amount can be accurately calculated from their mass
- pure form / known chemical formula/ easy to store/ higher molecular mass
preparing a standard solution
- weigh the pure solid on balance
- transfer to a volumetric flask w funnel
- rinse any remaining solid p w deionised water
- half fill flask and stopper it - swirl so particles will dissolve
- add deionised water up to calibration line
-stopper the flask and shake so even concentration dispersed throughout
dilution equation
C1V1=C2V2
what are the implications if dilutions are / are not performed
- standard solution = if X diluted then higher conc of solution and larger or very small titres
equivalence point
- point where exact mole ratio is reached
- point in reaction when neither reactant is in ecess
end point
when indicator used in reaction results in a colour change
rinsing - burette or pipette
rinse with acid or base that will be put in it
- with water = diluted
rinsing- volumetric + conical flask
rinse with deionised water
strong acid strong base - pH curve
equivalence point approx. 7
strong acid weak base - pH curve
equivalence point below 7 pH
strong base weak acid
equivalence point above 7 pH
problematic form of pH curve?
weak acid+ weak base
x sudden change so x determine eq point
volumetric analysis
an analytical technique that measures volume - analyses solution
what does rinsing pippette or burette with deionised water do
dilution - require less or more of titre to neutralise - change in conc
adsorption
adhering to stationary phase
why does seperation occur in chromatography
- different molecules = diff speeds
- different attractions to s and m phase so desorb and adsorb at different rates
- strongest adsorption = travels least distance and most soluble = greatest distance
why do primary standards have high molar mass
allow for discrepencies in calculations - less impact
density
mass/ volume
calibration curves - inaccurate or not?
interpolation
extrapolation
m/z
mass to charge
chemical shift
difference in energy needed to change spin state in sample compared to TMS
HPLC chromatogram: the peak at __ minutes is beyond the scope of the vertical axis. how to solve the issue?
conc. = very high so should be diluted to fit the range of the standards
