synthesis and analytical techniques Flashcards
(18 cards)
how to purify an organic solid
1) Dissolve solid in minimum amount of hot solvent
2) Allow to cool and recrystallise
3) Filter under reduced pressure (Buchner funnel)
4) Wash with cold solvent and dry
ways to know a reactant is completely used up
-heat to a constant mass
-use excess of a reactant
colour of halides in water
Cl2- pale green
Br2- orange
I2- brown
colour of halides in organic solvent (cyclohexane) (top layer)
Cl2- pale green
Br2- orange
I2- violet
carbonate and sulphate test
carbonate - DILUTE nitric acid-effervescence
sulphate - barium nitrate
how to test for CO2
bubble gas through limewater - limewater turns cloudy
preparing a standard solution
WARY- weigh solid
DOLPHINS- dissolve solid in beaker using distilled water
TEACH - transfer to volumetric flask
RED - rinse beaker into into volumetric flask
DROOPY - drop by drop add distilled water until bottom of meniscus is on level with the graduation line
IGUANAS - invert several times
how to assign priority in E/Z isomers
atomic number of all the atoms bonded to the FIRST carbon on each side.- max of 3
high = high priority
conditions for cis/trans isomerism
must have the same molecule on each side of the C=C bond. e.g. hydrogen or Cl
test for ammonium ions
damn litmus paper turns blue
what is CDCl3 used for
general solvent in HNMR
what is Si(CH3)4 used for
tetramethylsaline (TMS) is used as a standard in NMR
what is CCl4 used for
general solvent
what is the change in rate of hydrolysis as you go down group 7 of haloalkanes
rate of hydrolysis increases because the CARBON-HALOGEN BOND ENTHALPY decreases
equation for nucleophilic substitution-of haloalkane with NaOH
haloalkane + NaOH(aq)——-> alcohol + Hx
NEEDS REFLUX
formation of a nitrile
haloalkane + ethanolic CN⁻ —–> nitrile + Hx
IN ETHANOL so no alcohol is formed
formation of an amine
-haloalkane + excess NH3———>ammonium salt
-ammonium salt + NaOH—-> amine
this is in ethanol so NH3 is ETHANOLIC which means that both the haloalkane and NH3 are dissolved and stops water from acting as a nucleophile
why is benzene harder to halogenate than an alkene
in an alkene the electrons are LOCALISED
in benzene the electrons are DELOCALISED
localised electrons have a higher electron density so are more susceptible to electrophilic attack
