2. INTRODUCTION
• Thiophene is a heterocyclic compound with the formula C4H4S
• It consists of a planar five-membered ring, it is aromatic as indicated by its
extensive substitution reactions
• Thiophene is aromatic because it has six π electrons in a planar, cyclic,
conjugated system
• It occurs in the light oil fraction of coat-tar and is usually present as an impurity in
commercial benzene.
3. PREPARATION METHODS
• (1) By passing a mixture of acetylene and hydrogen sulphide through a tube
containing aluminium oxide at 400°C.
4. (2) BY HEATING SODIUM SUCCINATE WITH
PHOSPHOROUS TRISULPLSIDE
5. • 3. By the high-temperature (650 C) reaction of sulphur with butane. (Commercial
Method of Preparation).
6. FROM COAL TAR BENZENE
• The boiling points of thiophene and benzene are so close together that they
cannot be separated by distillation.
• Thiophene may be separated from benzene by shaking the mixture with cold
concentrated sulphuric acid which sulphonates it more readily than benzene
• Thiophene sulphonic acid is then removed from the solution by the usual
methods and converted into thiophene by super-heated steam
• Best method of removing thiophene from benzene is by shaking with Raney
nickel.
7. • A simple method is to boil benzene-thiophene mixture with mercuric acetate.
• Thiophene s converted into the insoluble 1-merouriacetate which regenerates
thiophene on boiling with concentrated hydrochloric acid.
8. PHYSICAL PROPERTIES
• Thiophene is a colourless liquid, boiling point 84 C, with an odour very similar to
that of benzene
• It is insoluble in water, but miscible with most organic solvents
• It is comparatively stable to oxidation
• Thiophene also has alternate double and single bond structure and the aromatic
character in it is very pronounced as compared to furan and pyrrole.
9. CHEMICAL PROPERTIES
• Thiophene is 300 times more reactive than benzene
• Thiophene does not show any basic properties
• It is much more stable to acids than either pyrrole or furan
• Thiophene does not undergo the Diels-Alder reaction unlike pyrrole or furan
10. 1) ELECTROPHILIC SUBSTITUTIONS:
• Thiophene, like furan and pyrrole, undergoes electrophilic substitution reactions
primarily at C-2. Substitution at C-3 occurs only when both of the 2-positions (α
and ά) are already occupied.
11.
12. (2) REDUCTION:
• Thiophene may be hydrogenated by means of sodium amalgam and ethanol to
tetrahydrothiophene.
14. PHARMACEUTICAL IMPORTANCE OF THIOPHENE
• In medicine, thiophene derivatives shows antimicrobial, analgesic and anti-
inflammatory, antihypertensive, and antitumor activity
• It is commonly used as a building block in drugs
• It is considered to be a structural alert, as its metabolism can lead to the
formation of reactive metabolites
• Several commercially available drugs such as Tipepidine, Timepidium Bromide,
Dorzolamide, Tioconazole, Citizolam, Sertaconazole Nitrate contain thiophene
nucleus
