prove ethylbenzene is aromatic according to huckel rule
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The Hückle Rule
Most aromatic compounds contain a benzene ring or a related structure. What is responsible for the characteristic stability of benzene and its unique reactivity? Several general criteria must be met if a molecule is to be aromatic.
1.
An aromatic molecule must be cyclic.
2.
An aromatic molecule must be planar.
3.
An aromatic ring must contain onlysp2-hybridized atoms that can form a delocalized system of π molecular orbitals.
4.
The number of π electrons in the delocalized π system must equal 4n + 2, where n is an integer.
The “4n + 2 rule” was proposed by E. Huckel, and is known as the Hückel rule. The theoretical basis for this rule is beyond the scope of this text. However, based on the Huckel rule, cyclic π systems with 6 (n = 1), 10 (n = 2), and 14 (n = 3) electrons are aromatic. Benzene meets the criteria for aromaticity for n = 1. We will discuss examples in the following section for various 6, 10, and 14 π electron systems. We will also see that aromatic compounds can contain atoms other than carbon (Section 5.3).
Some cyclic polyenes with alternating single and double bonds are not aromatic. These compounds do not obey the Huckel rule. Two examples are cyclobutadiene (four π electrons) and cyclooctatetraene (eight π electrons). Both compounds undergo addition reactions of the kind we have discussed, and have none of the characteristics of benzene.
So,ethylbenzene is aromatic.
Hope it helps
Gitali...
Most aromatic compounds contain a benzene ring or a related structure. What is responsible for the characteristic stability of benzene and its unique reactivity? Several general criteria must be met if a molecule is to be aromatic.
1.
An aromatic molecule must be cyclic.
2.
An aromatic molecule must be planar.
3.
An aromatic ring must contain onlysp2-hybridized atoms that can form a delocalized system of π molecular orbitals.
4.
The number of π electrons in the delocalized π system must equal 4n + 2, where n is an integer.
The “4n + 2 rule” was proposed by E. Huckel, and is known as the Hückel rule. The theoretical basis for this rule is beyond the scope of this text. However, based on the Huckel rule, cyclic π systems with 6 (n = 1), 10 (n = 2), and 14 (n = 3) electrons are aromatic. Benzene meets the criteria for aromaticity for n = 1. We will discuss examples in the following section for various 6, 10, and 14 π electron systems. We will also see that aromatic compounds can contain atoms other than carbon (Section 5.3).
Some cyclic polyenes with alternating single and double bonds are not aromatic. These compounds do not obey the Huckel rule. Two examples are cyclobutadiene (four π electrons) and cyclooctatetraene (eight π electrons). Both compounds undergo addition reactions of the kind we have discussed, and have none of the characteristics of benzene.
So,ethylbenzene is aromatic.
Hope it helps
Gitali...
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