Difference Between Benzenoid and Non Benzenoid

The key difference between benzenoid and non benzenoid compounds is that benzenoid compounds contain at least one benzene ring in the molecule whereas non benzenoid compounds have no benzene rings.

An aromatic compound is a cyclic, planar molecule with a ring of resonance bonds. These structures are more stable than normal ring structures. Both benzenoid and non benzenoid compounds are aromatic compounds. Therefore, all aromatic compounds are not necessarily benzenoid compounds.

CONTENTS

1. Overview and Key Difference
2. What is Benzenoid
3. What is Non Benzenoid
4. Similarities Between Benzenoid and Non Benzenoid
5. Side by Side Comparison – Benzenoid vs Non Benzenoid in Tabular Form
6. Summary

What is Benzenoid

Benzenoid compounds are molecules that have at least one benzene ring in its chemical structure. A benzene ring is a cyclic structure having six carbon atoms as the ring members. It has three pi bonds (double bonds) and three sigma bonds arranged in an alternative pattern. Therefore, we call this pattern a conjugated pi system.

Since the molecule has double bonds due to benzene ring, the molecule is an unsaturated compound with extra stability provided by the conjugated pi system.

What is Non Benzenoid?

Non benzenoid compounds are aromatic molecules that do not have benzene rings in its chemical structure. Although a benzene ring is absent, these molecules have a conjugated pi system. The ring structures of these compounds have around 5-7 carbon atoms.

The aromatic nature arises due to the presence of conjugated pi system. This conjugated pi system provides the molecule with extra stability. Some common examples include azulenes, Oxaazulanones, Pentafulvene, Tropones & Tropolones, etc.

What are the Similarities Between Benzenoid and Non Benzenoid?

• Both are cyclic structures
• Benzenoid and Non Benzenoid are aromatic compounds with conjugated pi systems
• Both Benzenoid and Non Benzenoid exhibit an extra stability

What is the Difference Between Benzenoid and Non Benzenoid?

Although both benzenoid and non benzenoid compounds are aromatic compounds, they have few differences between them. The difference is the presence of a benzene ring in these two compounds. In benzenoid compounds there are benzene rings present that gives cause to its name whereas a benzene ring is absent in non benzenoid compounds. These structural differences definitely affect the chemical properties and reactivity of these compounds.

Summary – Benzenoid vs Non Benzenoid

Both benzenoid and non benzenoid compounds are aromatic structures having a conjugated pi system. Therefore, both these structures show extra stability. The difference between benzenoid and non benzenoid compounds is that benzenoid compounds contain at least one benzene ring in the molecule whereas non benzenoid compounds have no benzene rings.

Reference:

1. “Non Benzenoid Aromatic Compounds.” Mannich Reaction | Mannich Reaction Mechanism | Chemistry@TutorVista.com. Available here 
2. “Aromaticity.” Wikipedia, Wikimedia Foundation, 6 June 2018. Available here  

Image Courtesy:

1.’Toluene 200’By Emeldir (talk) – Own work, (Public Domain) via Commons Wikimedia  
2.’Azulene struttura’By Paginazero – mio disegno, (Public Domain) via Commons Wikimedia