mod 6
- Created by: Simbaaax
- Created on: 18-06-17 16:46
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- analysis
- chromatography
- stationary phase= fixed in place, liquid in GC (mixtures have diff attractions to each phase) or solid in TLC (components of mixture adsorbed by different amounts)
- = seperation technique to identify chemicals in mixture
- mobile phase= moves in definite direction; inert gas in GC or liquid solvent in TLC
- substances very attracted to mobile phase and not stationary will travel far
- TLC
- stationary= glass (inert material) covered with absorbent chemical e.g. aluminium oxide
- = to check purity of sample or determine extent of chemical reaction
- mobile= organic solvent, moves in one direction up plate
- Rf
- distance by component/ distance by solvent
- not always same as data table bc diff solvent used// use control spots for direct comparison
- similar compounds have similar Rf values & chemicals that are very attracted to mobile phase may not be separated
- GC
- = separate volatile chemicals in a mixture
- often connected to mass spectrometer for further analysis
- stationary= solid or liquid coating on coiled tube; usually a Hydrocarbon w/ high B.P.
- mobile= unreactive carrier gas e.g. Helium or N2
- results produce CHART of absorption against time (x axis= retention time)
- retention time= time taken for component to pass from column inlet to the detector // compare to known values to identify component
- = separate volatile chemicals in a mixture
- NMR
- Deuterium= isotope of hydrogen + produces no signal
- TMS= 1 sharp singlet, non-toxic, low B.P. + volatile (easily removed) inert
- isotopes of 1H and 13C known to have spin property; in a spectrometer compounds w/ these isotopes are put into a large magnetic field
- the radiowave energy used to force spin to flip + change direction// energy required to flip depends on env the atom is in
- internal standard= TMS (12 equivalent protons)
- = non destructive analytical technique
- long spots indicate more than one chemical present
- solvent; dissolve molecule . Dont use e.g. benzene bc produces a peak itself. Deuterium= heavy water
- equivalent protons; H bonded to same atoms so experience same magnetic field in NMR spectrometer
- proton exchange = D2O shake, common deuterated solvent is CDCl3
- 1) mass spec, 2) infrared 3) high resolution NMR (H NMR) 4)C-13 NMR
- organic synthesis
- independent variable= YOU CHANGE e.g. temp
- dependent variable= YOU MEASURE
- prep; slow flammable + volatile chemicals refluxed w/ VERTICAL LIEBIG CONDENSER, may cause further substitutions so DISTILATION used
- VOLUMETRIC FLASK= accurate, specific amount of liquid, accurate dilutions or standard sols
- seperation= remove water soluble impurities; impure product at top (organic) and aqueous layer always at bottom. (organic layer = less dense= floats) DISCARD AQUEOUS LAYER
- water soluble impurities dissolved in aqueous layer
- organic layer has trace amounts of impurities; add anhydrous salt e.g. MgSO4, binds to water, filter to remove drying agent
- Lab exp= controlled variables, kept constant, meaningful results
- DISTILATION= gentle heating, substances evaporate in order of increasing B.P. Some products may react further e.g aldehydes
- VOLATILE LIQUID= purified via redistillation; heat impure product, when liquid you want boils, place flask at open end of condenser. Use thermometer to tell u when its boiling, when thermometer changes move flash bc diff liquid
- percentage error= uncertainty/ reading x100
- RECRYSTALLISATION= If solid; 1)hot solvent + impure solid (until JUST dissolves). Saturated solution of impure product. 2)cool down- form crystals (small amounts of impurities left in sol) 3)remove crystals via filtration under reduced pressure w/ BUCHNER FUNNEL. Wash with ice cold solvent and pat dry
- solvent= solid soluble when hot, almost insoluble when cold. (soluble in cold= stays in sol after cooling = low yield)
- determine M.P: 1) solid into capillary tube + beaker of oil with thermometer. 2)heat + stir till solid melts, compare to database to determine purity
- Test for carbonyls
- BRADYS REAGENT = aldehydes& ketones; (2,4-DNP, methanol, conc H2SO4), bright orange ppt.
- identify : 1) filter + recrystallised 2)measure M.P. 3)compare M.P to database
- amine group on DNP reacts w/ carbonyl
- TOLLENS REAGENT (ammonical silver nitrate) = aldehydes ONLY. (NaOH + AgNO3, brown ppt redissolved via dilute NH3 (NAN)
- silver mirror formed; Ag reduced: Ag+ +e- -> Ag(s)
- aldehyde oxidised to carboxylic acid (ketones= secondary, dont oxidise further
- BRADYS REAGENT = aldehydes& ketones; (2,4-DNP, methanol, conc H2SO4), bright orange ppt.
- chromatography
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