[Chemistry Class Notes] Non Aromatic Compounds Pdf for Exam

Non-aromatic particles are each non-cyclic, non-planar, or do not hold a comprehensive conjugated π system inside the ring. A compound in a cyclic form that does not demand a continuous form of an overlapping ring of p-orbitals needs not be considered aromatic or even anti-aromatic. Hence, these are termed as non-aromatic or aliphatic. The electronic energy of non-aromatic compounds is the same as its open-chain counterpart. Non-aromatics do not contain such a ring system with a delocalized electron cloud. We will learn about aromatic compounds and anti-aromatic compounds below. Non-aromatic compounds are those which do not satisfy the conditions applied to identify aromatic and anti-aromatic compounds.

Non-Aromatic Compounds Examples

All aliphatic compounds are non-aromatic. A few examples of non-aromatic compounds are as follows:

• 1-hexyne,

• 1-Neptune,

• 1-octyne,

• 1-online,

• 1, 4-cyclohexadiene,

• 1, 3, 5-cycloheptatriene,

• 4-vinyl cyclohexene,

• 1, 5, 9-cyclo deca triene.

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Aromatic Compounds

Aromatic compounds are the second vital element of crude oil, consisting of stacks of highly polymerized aromatic structures (average of 16 rings), completing the list of major oil hydrocarbon components. According to the Huckel Rule, most aromatic compounds contain a benzene ring or a related structure. If a compound or a molecule meets the following criteria, then these are aromatic compounds:

1. An aromatic molecule must be cyclic.

2. An aromatic molecule must be planar.

3. An aromatic compound ring should consist of only sp2-hybridized atoms. These atoms can form a delocalized system of π molecular orbitals.

In the delocalized π system, the number of π electrons must be equal to 4n + 2, where n is an integer.

4. Huckel proposed the “4n + 2 rule” and is known as the Huckel rule.

As expressed by benzene and naphthalene, aromatic compounds are a group of compounds, which occupy a very important position in organic chemistry. Aromatic compounds display individual properties in their structures and magnetic properties besides stability and are called roundly having aromaticity.

Anti-Aromatic Compounds

Anti-aromatic compounds are compounds consisting of a cyclic molecule with a π electron system with higher energy due to the presence of 4n delocalized (π or lone pair) electrons. Exceptionally from aromatic compounds, which reflect Huckel’s rule and are deeply stable, anti-aromatic molecules are highly uncertain and extremely reactive. They may vary in shape to withdraw anti-aromatic particles’ unstable nature, shifting non-planar, consequently breaking some π intercommunications. Concerning the diamagnetic ring current existing in aromatic compounds, anti-aromatic compounds have a paramagnetic ring current. Anti-aromatic compounds can be thermodynamically recognized by estimating the energy of the cyclic conjugated pi-electron method. The energy will always remain higher than the reference compound used for the comparison.

Anti-aromatic particles are cyclically conjugated, must contain (4n) pi electrons, and are flat.

Example of Anti-Aromatic Compound

Pentalene is an example of an anti-aromatic compound that has been well studied experimentally for years. It is dicyclic, planar, and has eight π-electrons. Anionic and dicationic cases of Pentalene are aromatic since they follow Huckel’s 4n +2 π-electron rule.

State the Difference between Aromatic, Non-Aromatic, and Anti-Aromatic Compounds

The clear differences between aromatic, non-aromatic, and anti-aromatic compounds based on stability, delocalization, Pi electrons, and reactivity are  as listed below:

Aromatic Compounds

• Have benzene cycle in their structure and have 4n + 2 pi electrons.

• Have a greater % of carbon than non-aromatic compounds.

• Don’t show the bear test or bromine test.

• Stable.

• Mainly show nucleophilic replacement reactions and are less reactive.

• Show resonance in their structure.

• Examples – benzene, naphthalene, pyridine, etc.

Anti-Aromatic Compounds

• Cyclic compounds but haven’t a benzene cycle.

• Aliphatic compounds.

• Highly unstable.

• Anti-aromatic compounds are highly reactive.

• Anti-aromatic compounds have 4n pi electrons.

• Examples – cyclobutadiene, cyclohexadiene dication or dianion, etc.

Non-Aromatic Compounds

• It can be chained or cyclic but doesn’t have a benzene cycle and the number of pi electrons is not applicable for non-aromatic compounds.

• Saturated or unsaturated compounds.

• Stable.

• Don’t show resonance in their structure.

• Mainly show electrophilic reactions and are less reactive.

• Unsaturated inorganic compounds show bear and bromine tests.

• Examples – alkanes, alkenes, alkynes.

• Don’t show resonance in their structure.