What is a Pyrrole?
Pyrrole is a five-membered heterocyclic organic compound having the general formula C4H4NH. It is a colourless volatile liquid that darkens on exposure.
It consists of two pi bonds and one lone pair of electrons contributing to a pi system. Thus it has six pi electrons.
Table of Content
- Introduction of Aromatic Compounds
- What is Huckel’s rule of Aromaticity?
- Pyrrole is Aromatic or not?
- Frequently Asked Questions – FAQs
Introduction of Aromatic Compounds
Aromatic Compounds or Aromatics are unsaturated compounds containing conjugated planar rings escorted by delocalised pi-electron clouds. It consists of delocalised pi electrons and sigma bonds between carbon atoms in the ring.
- Any compound obeying Huckel’s rule of aromaticity is classified as an aromatic compound.
Further, we can classify aromatic compounds into two categories based on their structure.
- Benzenoid Aromatic Compound
- Non-Benzenoid Aromatic Compound
Benzenoid Aromatic Compound
A Benzenoid Aromatic compound contains a benzene ring in its structure. Toluene, Phenol, Aniline, Acetophenone, Benzaldehyde, Benzoic Acid, Benzonitrile, ortho-Xylene, and Styrene are examples of Benzenoid Aromatic compounds.
Non-Benzenoid Aromatic Compound
A Non-Benzenoid Aromatic compound does not contain a benzene ring in its structure. Furan, Pyrrole and Thiopene are examples of Non-Benzenoid Aromatic compounds.
What is Huckel’s rule of Aromaticity?
Huckel’s rule is a criterion used to characterise the aromaticity of a compound. If a compound obeys Huckel’s rule of aromaticity, it is classified as an aromatic compound. In contrast, if a compound doesn’t follow Huckel’s rule of aromaticity, it can either be anti-aromatic or non-aromatic.
Huckel states that a compound will be aromatic if,
- It is cyclic.
- It is planar.
- It has a continuous ring of p atomic orbitals.
- It contains (4n + 2) π electrons in a conjugated system of p orbitals.
Pyrrole is Aromatic or not?
Pyrrole is a planar five-membered heterocyclic organic compound having the general formula C4H4NH. It is a colourless volatile liquid that darkens on exposure.
It consists of two pi bonds and one lone pair of electrons contributing to a pi system. Thus it has six pi electrons.
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Pyrrole is Aromatic or not? |
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|---|---|---|
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S No. |
Huckel’s rule Criterion |
Obeys |
|
1. |
It should be cyclic. |
Yes |
|
2. |
It should be planar. |
Yes |
|
3. |
It should have a continuous ring of p atomic orbitals. |
Yes |
|
4. |
It should contain (4n + 2) π electrons in a conjugated system of p orbitals. |
Yes |
|
Pyrrole obeys all the parameters of Huckel’s Rule. Therefore, it is an aromatic compound. |
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Frequently Asked Questions on Pyrrole is Aromatic or not?
What is a pyrrole?
Pyrrole is a five-membered heterocyclic organic compound having the general formula C4H4NH. It consists of two pi bonds and one lone pair of electrons contributing to a pi system. Thus it has six pi electrons.
What are aromatic compounds?
Aromatic Compounds or Aromatics are unsaturated compounds containing conjugated planar rings escorted by delocalised pi-electron clouds. It consists of delocalised pi electrons and sigma bonds between carbon atoms in the ring.
- Any compound obeying Huckel’s rule of aromaticity is classified as an aromatic compound.
What is Huckel’s Rule?
Huckel states a criterion to characterise the aromaticity of a compound. He states that a compound will be aromatic if,
- It is cyclic.
- It is planar.
- It has a continuous ring of p atomic orbitals.
- It contains (4n + 2) π electrons in a conjugated system of p orbitals.
Is pyrrole aromatic?
Yes, pyrrole obeys all the parameters of Huckel’s Rule. Therefore, it is an aromatic compound.
Are all cyclic compounds aromatic?
No, all cyclic compounds are not aromatic. It must follow all the parameters of Huckel’s rule to be characterised as an aromatic compound.
Example: Cyclohexane is a cyclic compound, but it is not aromatic.
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