Page 39 - Org 3 theoritical book 2024-25

Clinical Pharmacy PharmD - 2024/2025 Level 2 Pharmaceutical Organic Chemistry-3 (PC 305)
2- Furan and its derivatives

Furan is the oxygen analogue of the 5-membered heterocyclic aromatic compounds.

General methods of preparation:

1) From pine wood:

• The polysaccharides of pine wood (pentosans) are first hydrolyzed by conc.H 2SO 4

to give furfural (furan-2-carboxaldehyde)

• Furfural is then oxidized by Ag 2O to furoic acid, which is decarboxylated by
heating with sodalime, or by thermal decomposition to give furan.

H SO
Polysaccarides 2 4 CHO
(C H O ) O
4 n
5 8
pentosans furfural
(furan-2-carboxaldehyde)
Ag O
2

Sodalime
O -CO 2 O COOH
furan furoic acid
(furan-2-carboxylic acid)
2) Paal-Knorr synthesis

• By heating 1,4-dicarbonyl compounds with dehydrating agents as P 2O 5, ZnCl 2 or
H 2SO 4...etc.

A. Properties of furan:

o
• Furan is liquid with boiling point 32 .
• It is relatively stable towards air and alkali.

• It polymerizes to insoluble dark resin under the effect of acids.