In 1931, who recognised that an aromatic compound must have an odd number of pairs of electrons, which can mathematically be written as 4n + 2 (n = 0, 1, 2, 3 etc.)?

Question

Question

This question was previously asked in

SSC CGL 2022 Tier-I Official Paper (Held On : 12 Dec 2022 Shift 1)

Answer 1

The correct answer is Erich Huckel.

Key Points

Erich Huckel was a German chemist and physicist.
He proposed a theory in 1931 to help determine if a planar ring molecule would have aromatic properties.
Erich Huckel recognized that an aromatic compound must have an odd number of pairs of electrons.
His rule states that a cyclic, planar molecule is considered aromatic if it has 4n+2 pi electrons.
This rule is known as Huckel's Rule.

Additional Information

Pi bond:- Bond formed by the same phase overlap of atomic orbitals along a direction perpendicular to the internuclear axis is called pi bond.
Pi electrons:- An electron that resides in the pi bond (s) of a double bond or a triple bond or in a conjugated p orbital is called pi electron.
System is divided into aromatic, anti-aromatic, and non-aromatic based on no. of pi electrons-
- Aromatic system - The number of pi electrons in an aromatic system is determined by N = 4n+2 (n is an integer)
- Anti-aromatic system - The number of pi electrons in an anti-aromatic system is determined by N = 4n (n is an integer)
- Non-aromatic - If a compound does not have a continuous ring of conjugated p orbitals in a planar module, then it is called non-aromatic.