Non Aromatic Compounds

Bookmark added to your notes.
View Notes
×

Non-Aromatic Compounds Definition

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 need not be considered as aromatic or even antiaromatic. Hence, these are termed as nonaromatic 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 antiaromatic compounds below. Non Aromatic compounds are those which do not satisfy the conditions applied to identify aromatic and antiaromatic compounds.


Non-aromatic Compounds Examples

All aliphatic compounds are non-aromatic. Few examples of non-aromatic compounds are:

1-hexyne,

1-heptyne,

1-octyne,

1-nonyne,

1, 4-cyclohexadiene,

1, 3, 5-cycloheptatriene,

4-vinylcyclohexene,

1, 5, 9-cyclo deca triene.

[Image will be Uploaded Soon]


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 Huckle 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.

E. 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 engross 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

Antiaromatic 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, antiaromatic molecules are highly uncertain and extremely reactive. They may vary in shape to withdraw antiaromatic particles' unstable nature, shifting non-planar, consequently breaking some π intercommunications. Concerning the diamagnetic ring current existing in aromatic compounds, antiaromatic compounds have a paramagnetic ring current. Antiaromatic compounds can be thermodynamically recognized by estimating the energy of the cyclic conjugated pi-electron method. The energy will always remain higher than the used reference compound for the comparison.

Antiaromatic particles denote cyclically, conjugated, must (4n) pi electrons, and are flat.


Example of Anti Aromatic Compound

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


State The Difference Between Aromatic, Nonaromatic, And Anti Aromatic Compounds

The clear difference between aromatic, non-aromatic, and antiaromatic compounds based on stability, delocalization, Pi electrons, and reactivity is as listed below:


 Aromatic Compounds-

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

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

  • Don't show 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

Antiaromatic Compounds-

  • Cyclic compounds but haven't benzene cycle.

  • Aliphatic compounds.

  • Highly unstable

  • Antiaromatic compounds are highly reactive.

  • Antiaromatic compounds have 4n pi electrons.

  • Examples - cyclobutadiene, cyclohexane, 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.

Solved Examples

Question 1: Find the Non-aromatic Compound Among the Listed Elements:

[Image will be Uploaded Soon]

Solution: Cyclopentadiene is a non-aromatic compound.

Cyclopentadiene does not follow Huckel's Rule, as it has sp3 carbon in the ring.

FAQ (Frequently Asked Questions)

Question 1: What is the Reason Behind Calling Cycloheptatrienyl a Non Aromatic Compound?

Answer: That happens because of Huckel's rule of aromaticity. The cycloheptatrienyl has 8 electrons, which translates as 4n electrons, not the 4n+2 as suggested by Huckel. If the MOs are designed for both rounds, you will notice that placing 4n electrons will expand in a diradical molecule, not steady as it already seems. A quick skill for executing that is using Frost's circle. All that is needed is to mark the parallel polygon in a circle and be sure that you have a vertex touching the circle as low as possible. The vertices will give you the emotional energy of the MOs.

Question 2: What is the Product Formed When Benzene Reacts with Acetyl Chloride in the Presence of Anhydrous AlCl₃?

Solution: AlCl₃ is estimated to be a Lewis Acid or, in more simplistic terms, an "electron hungry species." So, when it gets to find Acetyl Chloride (CH₃COCl), it extracts the -Cl minus from the latter and itself gets modified into AlCl₄ minus. Then it will get quite stable as its need will be satisfied.


Then it will leave an electrophile -COCH₃ minus as we all know that benzene goes through aromatic electrophilic substitution reactions. Hence, the other electrophile gets connected to the benzene ring, thereby creating Acetophenone (C₆H₅COCH₃). AlCl₃ is also a catalyst in this reaction because it emits its Cl minus after the reaction, and HCl is produced as a by-product.