ORGANIC
CHEMISTRY
AL CHEM REVIEW
AL CHEM Written Practical
[Organic Chemistry]
~ Organic Synthesis ~
Organic Acid
How to separate How to purify
Organic Base the product from the product??
rxn mixture ??
(solid/liquid)
Others
p.1
Common Separation Method
Solvent Extraction
(use separating
funnel)
Distillation
Fractional Distillation
p.2
Common Purification Method
Recrystallization
Na2SO4 / MgSO4
Drying
Decolorization
(adding activated
charcoal)
p.3
1997 P.I Q.8(b)
You are provided with a mixture of two liquids,
hexan-1-amine (U) and ethyl ethanoate (W).
Outline an experimental procedure, based on a
solvent extraction process, to enable U
to be separated from W.
(3M)
p.4
Add ether and dilute HCl.
*Shake in a separating funnel.
The ether layer will contain CH3COOC2H5.
Basify the aqueous layer with excess NaOH(aq).
and then extract with ether.
The ether layer will contain CH3(CH2)5NH2
p.5
1998 P.I Q.8(b)
You are provided with a mixture of two
liquids, heptanoic acid and hexan-3-one.
Outline an experimental procedure, based on
a solvent extraction process, to
isolate pure heptanoic acid in good yield.
(3M)
p.6
Add ether and dilute NaOH / Na2CO3 / NaHCO3.
*Shake in a separating funnel.
Ether layer contains hexan-3-one, aqueous layer
contains CH3(CH2)5COO-Na+.
Add dilute HCl to aqueous layer generate
CH3(CH2)5COOH.
Extract with ether,
distill ether to obtain heptanoic acid.
p.7
1999 P.I Q.8(b)
In an experiment to prepare 1-bromobutane, a
mixture of butan-1-ol, potassium bromide and
concentrated sulphuric (VI) acid was heated
under reflux for 30 minutes.
(i) Draw a labelled diagram of the set-up used.
(ii) Suggest how to isolate 1-bromobutane
from the reaction mixture.
(4M)
p.8
p.9
Use dropper to remove the aqueous layer
/ remove aq. component by simple distillation.
Shake the organic layer with Na2CO3(aq) /
NaHCO3(aq) in a separating funnel until the excess
acid has completely been neutralized.
Keep the denser organic layer.
Add anhydrous Na2SO4 to the organic layer until the
liquid becomes clear.
Decant liquid to get rid of Na2SO4 particles.
Distill liquid and collect vapour at the boiling point
of 1-bromobutane.
p.10
1995 P.I Q.4(b) (i), (ii)
Describe the experimental procedure by
which you would recrystallize a sample
of impure benzoic acid.
How would you test
product?
the purity of the
(4M)
p.11
Dissolve in minimum quantity of hot water using
boiling tube.
Filter the solution while it is hot through fluted filter
paper into beaker.
Leave for crystals to form.
Filter off the crystals and wash with minimum
amount of cold water.
Dry between filter paper until not damp.
Test the purity of product by melting point
determination, compare with literature value.
p.12
2001 P.I Q.8
p.13
p.14
Other Important Examples (1)
1990 P.1B Q.4(a)
Outline a chemical method to separate
X, Y and Z from each other.
OH
NH2
CH3
Br
X
1991 P.1B Q.5(a)
CH3
X
NH2
CH3
Y
Z
The amine X, C7H9N, may be prepared from
Y, C7H7NO2, by the reaction with excess
hot granulated tin and conc. HCl. If, in this
reaction, some Y remains unreacted,
suggest a procedure to isolate pure X from
the reaction mixture.
Y
NO2
p.15
Other Important Examples (2)
1992 P.1B Q.5(b)
An incomplete reaction of phenylamine
with ethanoic anhydride gave a liquid
mixture on cooling. Briefly oultine a
procedure, using separating funnel and
appropriate reagent(s), to isolate the
ethanoylation product.
p.16