AL CHEM REVIEW

AL CHEM REVIEW

ORGANIC CHEMISTRY

AL CHEM Written Practical

[Organic Chemistry][Organic Chemistry]

p.1

~ Organic Synthesis ~

Organic AcidHow to separateseparate the product from rxn mixture ??

How to purifypurify the product??

(solid/liquid)

Organic Base

Others

Common Common SeparationSeparation Method Method

p.2

Solvent ExtractionSolvent Extraction(use separating (use separating

funnel)funnel)

DistillationDistillation

Fractional DistillationFractional DistillationChemical

Method

Physical Method

Physical Method

Common Common PurificationPurification Method Method

p.3

RecrystallizationRecrystallization

DryingDrying

NaNa22SOSO44 / MgSO / MgSO44

DecolorizationDecolorization(adding activated (adding activated

charcoal)charcoal)

1997 P.I Q.8(b)

(3M)

p.4

You are provided with a mixture of two liquids, hexan-1-aminehexan-1-amine (U) and ethyl ethanoateethyl ethanoate (W). Outl

ine an experimental procedure, based on a solsolvent extraction processvent extraction process, to enable U to be separated from W.

p.5

Add Add etherether and dilute HCl. and dilute HCl.*Shake in a *Shake in a separating funnelseparating funnel..

The ether layer will contain CHThe ether layer will contain CH33COOCCOOC22HH55..

Basify the aqueous layer with excess NaOH(aq). Basify the aqueous layer with excess NaOH(aq). and then and then extract with etherextract with ether..

The ether layer will contain CHThe ether layer will contain CH33(CH(CH22))55NHNH22

1998 P.I Q.8(b)

(3M)

p.6

You are provided with a mixture of two liquids, heptanoic acidheptanoic acid and hexan-3-onehexan-3-one. Outline an

experimental procedure, based on a solvensolvent extraction processt extraction process, to isolate pure heptanoic acid in good yield.

p.7

Add Add etherether and dilute NaOH / Na and dilute NaOH / Na22COCO33 / NaHCO / NaHCO33..

*Shake in a *Shake in a separating funnelseparating funnel..

Ether layer contains hexan-3-one, aqueous layer Ether layer contains hexan-3-one, aqueous layer contains CHcontains CH33(CH(CH22))55COOCOO--NaNa++..

Add dilute HCl to aqueous layer generate CHAdd dilute HCl to aqueous layer generate CH33(C(C

HH22))55COOH.COOH.

Extract with etherExtract with ether, , distill ether to obtain heptanoic acid.distill ether to obtain heptanoic acid.

(4M)

p.8

1999 P.I Q.8(b)

In an experiment to prepare 1-bromobutane, a mixture of butan-1-olbutan-1-ol, potassium bromidepotassium bromide and cconcentrated sulphuric (VI) acidoncentrated sulphuric (VI) acid was heated under reflux for 30 minutes.

(i) Draw a labelled diagram of the set-up used.

(ii) Suggest how to isolateisolate 1-bromobutane from the reaction mixture.

p.9

p.10

Use dropper to remove the aqueous layerUse dropper to remove the aqueous layer/ remove aq. component by simple distillation./ remove aq. component by simple distillation.

Shake the organic layer with NaShake the organic layer with Na22COCO33(aq) / NaHCO(aq) / NaHCO33(a(a

q) in a q) in a separating funnelseparating funnel until the excess acid has c until the excess acid has completely been neutralized.ompletely been neutralized.

Keep the denser organic layer.Keep the denser organic layer.

Add Add anhydrous Naanhydrous Na22SOSO44 to the organic layer until the to the organic layer until the

liquid becomes clear.liquid becomes clear.

Decant liquid to get rid of NaDecant liquid to get rid of Na22SOSO44 particles. particles.

Distill liquid and collect vapour at the boiling point Distill liquid and collect vapour at the boiling point of 1-bromobutane.of 1-bromobutane.

1995 P.I Q.4(b) (i), (ii)

(4M)

p.11

Describe the experimental procedure by whic

h you would recrystallize a sample of impure benzoic acid.

How would you test the purity of the product?

p.12

Dissolve in Dissolve in minimum quantity of hot waterminimum quantity of hot water using using boiling tube.boiling tube.

Filter the solution while it is hot through fluted filter Filter the solution while it is hot through fluted filter paper into beaker.paper into beaker.

Leave for crystals to form.Leave for crystals to form.

Filter off the crystals and Filter off the crystals and wash with minimum wash with minimum amount of cold wateramount of cold water..

Dry between filter paper until not damp.Dry between filter paper until not damp.

Test the purity of product by melting point Test the purity of product by melting point determination, compare with literature value.determination, compare with literature value.

2001 P.I Q.8

p.13

p.14

1990 P.1B Q.4(a) Outline a chemical method to separate X, Y and Z from each other.

p.15

Other Important Examples (1)

OH NH2 CH3

Br

X Y Z

1991 P.1B Q.5(a) 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.

CH3

NH2

NO2

CH3

X

Y

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

Other Important Examples (2)