Table of Contents
Introduction of thiophene
It is the five membered heterocyclic compound containing sulphur(S) as a heteroatom. Thiophene is an organic compound composed of a five-membered ring of atoms. It has the chemical formula C₄H₄S and is one of the simplest aromatic compounds containing sulfur. Thiophene is an important industrial chemical used in various applications such as rubber synthesis, pharmaceuticals, agrochemicals, polymers, and dyes. Its derivatives are also used as materials for solar cells and organic light-emitting diodes (OLEDs). The name “thiophene” comes from the Greek word thios meaning sulfur. Thiophene has a distinctive smoky odor that can be smelled at low concentrations in the air.
Chemistry of thiophene
The ring atom in thiophene are Sp2 hybridised in which the Sp2 hybrid orbital overlap each other & the ‘S’ atomic orbitals of the four hydrogen forms C-C, C-S & C-H pi bonds. The unshared pair of electrons in the third Sp2 orbital on sulphur which is completely filled accounts for one of the sulphur lone pairs in the place of the ring.
Physical properties of thiophene
1. Thiophene is a colourless liquid.
2. It have an odour very similar to that of benzene.
3. Boiling point is 84°C.
4. It is insoluble in water, but miscible with most organic solvents.
Synthesis of thiophene
1. From sodium succinate
In this reaction, thiophene is synthesized by heating sodium succinate with phosphorus thiosulphate ion.
2. From n-butane
In this reaction, n-butane is heated with sulphur at 400°C and undergoes cyclization and formed thiophene.
3. Paal Knorr synthesis
In this reaction, acetonylacetone heated with phosphorus Penta sulphide and formed derivatives of pyrrole (2,5-dimethyl thiophene).
4. From acetylene
In this reaction, mixture of acetylene and hydrogen sulphide is passed through a tube containing alumina at 675K.
Chemical reactions of thiophene
When thiophene is react with nitric acid (HNO3), then it produce 2-nitrothiophene.
In this reaction, thiophene is react with sulphuric acid, then it produce 2-thiophenesulphonic acid.
3. Friedel craft acylation
In this reaction, thiophene is react with tin chloride(SnCl4), then it produce 2-acetylthiophene.
In this reaction, thiophene reduced with sodium in the presence of liquid ammonia give a mixture of 2-thiolen and 3-thiolen.
Medicinal uses of thiophene
1. They are widely used as building blocks is many agrochemical & pharmaceutical.
2. The benzene ring of a biologically active compound may after be relieved by a thiophene without loss of activity.
3. This is seen in NSAID julolidine, jiaprifenic acid, tenoxicam.
4. It is an antimicrobial agent: cefoxitin.
5. It is an anticancer agent: raltitrexed.
6. It is an antihypertensive agent: tiamenidine.
7. Thiophene derivatives are also useful as pesticides.