The key difference between pyrrole furan and thiophene is that pyrrole contains a –NH group in a five-membered carbon ring and furan contains an oxygen atom in a five-membered carbon ring whereas thiophene contains a sulfur atom in a five-membered carbon ring.
Pyrrole furan and thiophene are organic compounds. These are five-membered ring structures in which one carbon atom is replaced with a different group such as an amine group, an oxygen atom or a sulfur atom.
CONTENTS
1. Overview and Key Difference
2. What is Pyrrole
3. What is Furan
4. What is Thiophene
5. Side by Side Comparison – Pyrrole vs Furan vs Thiophene in Tabular Form
6. Summary
What is Pyrrole?
Pyrrole is a five-membered ring with the chemical formula C4H4NH. It is a heterocyclic compound in which a nitrogen atom contributes to the formation of the ring structure, along with four other carbon atoms. We can observe pyrrole as a volatile and colourless liquid at room temperature. However, upon exposure to normal air, the liquid readily darkens. Therefore, we need to purify it before using. The purification can be done via distillation immediately before use. Furthermore, this liquid has a nutty odour.
Figure 01: Structure of Pyrrole
Unlike some other five-membered heterocyclic rings such as furan and thiophene, pyrrole has a dipole in which the positive side of the ring is at the heteroatom (-NH group bears the positive charge). Pyrrole is a weakly basic compound.
Moreover, this compound occurs in nature as derivatives. For example, vitamin B12, bile pigments such as bilirubin, porphyrins, etc. are pyrrole derivatives. However, this compound is slightly toxic. In the industrial scale, we can synthesize pyrrole via the treatment of furan with ammonia. But, this reaction requires a solid catalyst as well.
What is Furan?
Furan is a five-membered ring structure containing an oxygen atom as a part of the ring. That means, an oxygen atom, along with four carbon atoms, forms the five-membered ring of furan. It is named as an aromatic heterocyclic ring. At room temperature, this compound exits as a colourless and highly volatile liquid. Also, this liquid is flammable as well. the boiling point of furan is very close to the room temperature. Besides, it has a strong, ethereal-like odour. When considering the toxicity, furan is highly toxic and can be carcinogenic in human.
Figure 02: Structure of Furan
Moreover, the aromaticity of furan is due to the delocalization of lone electron pairs of the oxygen atom into the ring. Also, this compound is considerably more reactive than benzene in electrophilic substitution reactions. It is because of the electron-donating behaviour of the oxygen atom.
In the industrial scale, we can produce furan via the decarbonylation of furfural in the presence of palladium catalyst. Or else, we can use another method in which oxidation of 1,3-butadiene is done in the presence of copper catalysts.
What is Thiophene?
Thiophene is a five-membered ring structure which has a sulfur atom and four carbon atoms in the ring. Therefore, it is an aromatic, heterocyclic ring. The chemical formula of the structure is C4H4S. It is a colourless liquid that has a benzene-like odour. There are many other similarities between thiophene and benzene such as reactivity. We can distinguish thiophene from benzene depending on the high reactivity of thiophene towards sulfonation.
Figure 03: Structure of Thiophene
When considering the production of thiophene, worldwide production involves the vapour phase reaction of carbon disulfide and butanol. Also, this reaction requires an oxygen catalyst and a high temperature.
What is the Difference Between Pyrrole Furan and Thiophene?
Pyrrole, furan, and thiophene are organic compounds. These are five-membered ring structures in which one carbon atom is replaced with a different group such as an amine group, an oxygen atom or a sulfur atom. Therefore, the key difference between pyrrole furan and thiophene is that pyrrole contains a –NH group in a five-membered carbon ring and furan contains an oxygen atom in a five-membered carbon ring, whereas thiophene contains a sulfur atom in a five-membered carbon ring.
Below infographic summarizes the difference between pyrrole furan and thiophene.
Summary – Pyrrole vs Furan vs Thiophene
Pyrrole, furan and thiophene are organic compounds. These are five-membered ring structures in which one carbon atom is replaced with a different group such as an amine group, an oxygen atom or a sulfur atom. Therefore, the key difference between pyrrole, furan and thiophene is that pyrrole contains a –NH group in a five-membered carbon ring and furan contains an oxygen atom in a five-membered carbon ring, whereas thiophene contains a sulfur atom in a five-membered carbon ring.
Reference:
1. “Pyrrole.” Wikipedia, Wikimedia Foundation, 28 Dec. 2019, Available here.
Image Courtesy:
1. “Pyrrole-2D-numbered” By Jynto (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Furan-2D-numbered” By Jynto – Own work (Public Domain) via Commons Wikimedia
3. “Thiophene-2D-numbered” By Jynto – Own work (Public Domain) via Commons Wikimedia