purification and characterisation of organic compounds Flashcards
PHYSICAL METHODS:
FOR SOLIDS :
crystallisation
impure substance+ solvent is heated in animal charcoal [adsorption occurs] and then filtered. On cooling it gives crystal of pure substance.
seeding
initiation of the process by adding crystals of pure substance
fractional crystallisation
occurs due to the difference in solubility of different compounds in a solvent
sublimation
solid to vapor on heating in which the impurities present do not sublime
eg: camphor , naphthalene
FOR LIQUIDS:
distillation
occurs due to the difference in boiling points .Occurs in presence of non volatile impurities
fractional distillation
occurs when the difference in B.P is low
eg: acetone and methanal
vacuum distillation
at reduced pressure
eg: glycerol
steam distillation
in liquids which are insoluble in water. Here liquid boil when the sum of V.P of organic liq + V.P of water = atmospheric pressure
eg: o-acetophenone and p-acetophenone
differential extraction
- by the means of seperating funnel
2. for the mix of 2 immiscible liq
chromatography
types:
- adsorption
- partition
adsorption chromatography
stationary phase is ion exchange resin or solid
mobile phase is liquid or gas
adsorbents are alumina ,silica gel, keiselguhr
liquid solvents are ether , alcohol, benzene
partition chromatography
stationary phase is liquid supported by inert solid
mobile phase is liquid or gas
CHEMICAL METHODS:
- amines are separated by hinsberg’s reagent
- acetic acid and pyroligneous acid[wood acid] are separated by forming calcium salt
- acids are separated by forming sodium derivatives and NaHCO3
- alcohol can be obtained from rectified spirit using quick lime and azeotropic distillation
Hinsberg reagent
C6H5SO2Cl-benzene sulfonyl chloride
azeotrope
constant boiling mixtures
