Aromatic Compounds: Definition and Examples

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In summary, an aromatic compound is a compound that contains a benzene ring or other ring of atoms, meets the other criteria listed, and is coplanar.
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At first I read that an aromatic compound is a compound that contains a ring with alternating double bonds in which the electrons are delocalized and the ring exhibits a greater stability than regular conjugated systems. That makes sense to me.

In Organic Chemistry by Clayden I read something different. In this book they say an aromatic compound is any compound that contains a benzene ring or other ring of atoms. Is that correct? If I'm not mistaken some rings have double bonds between their carbons and are not conjugated systems. Can an aromatic compound be a compound with a non conjugated ring system? In other words is any old cyclic compound considered an aromatic as long as it has a ring somewhere?
 
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MycelliumMan said:
At first I read that an aromatic compound is a compound that contains a ring with alternating double bonds in which the electrons are delocalized and the ring exhibits a greater stability than regular conjugated systems. That makes sense to me.

In Organic Chemistry by Clayden I read something different. In this book they say an aromatic compound is any compound that contains a benzene ring or other ring of atoms. Is that correct? If I'm not mistaken some rings have double bonds between their carbons and are not conjugated systems. Can an aromatic compound be a compound with a non conjugated ring system? In other words is any old cyclic compound considered an aromatic as long as it has a ring somewhere?

There's a set of parameters that define whether or not a ring is aromatic, actually.

Most obviously, it must be a of some sort ring of covalently bonded atoms with a delocalized group of pi electrons. It doesn't have to even be a single ring, but could be a fused ring or (I believe) even a bridged ring. For the delocalized electrons the easiest way to get them is alternating between single and double bonds.

Additionally, the ring needs to be coplanar, meaning it would lie flat if placed on a plane.

Perhaps most importantly, the delocalized cloud of electrons must contain and even number of electrons not divisible by four. This is determined by http://en.wikipedia.org/wiki/H%C3%BCckel%27s_rule" [Broken].
 
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Thank you for your question. I can understand the confusion between the two definitions of aromatic compounds. The key difference lies in the concept of delocalization of electrons in the ring system.

In the first definition, aromatic compounds are defined as compounds with a ring that has alternating double bonds and delocalized electrons. This is known as the Hückel's rule, which states that a compound must have a ring with 4n+2 π electrons (where n is an integer) to exhibit aromaticity. This delocalization of electrons leads to increased stability and unique chemical properties.

On the other hand, the second definition from Clayden's book refers to any compound that contains a benzene ring or other ring of atoms. This means that even if the ring does not follow the Hückel's rule, it can still be considered an aromatic compound. This definition is broader and includes compounds that may not exhibit the same level of stability and reactivity as traditional aromatic compounds.

To answer your question, yes, a compound with a non-conjugated ring system can still be considered an aromatic compound as long as it contains a ring with delocalized electrons. However, the level of aromaticity and stability may vary compared to traditional aromatic compounds.

In summary, both definitions are correct, but they may differ in the criteria for determining aromaticity. It is important to understand the concept of delocalization of electrons in the ring system to better understand aromatic compounds. I hope this helps clarify your doubts.
 

1. What are aromatic compounds?

Aromatic compounds are a type of organic compound that contains a ring of atoms with alternating single and double bonds. They are known for their strong and distinctive odors, which is where their name comes from. These compounds are also highly stable and have unique chemical properties.

2. How do you define aromaticity?

Aromaticity is a chemical property that describes the stability and unique properties of aromatic compounds. It is characterized by a ring of atoms with a delocalized electron system, meaning the electrons are not confined to a specific bond but instead spread out over the entire ring. This makes aromatic compounds highly stable and less reactive than other types of compounds.

3. What are some examples of aromatic compounds?

Some common examples of aromatic compounds include benzene, toluene, and xylene. These compounds are used in many industries, such as the production of plastics, rubber, and dyes. Aromatic compounds are also found in natural substances such as vanilla, cinnamon, and peppermint, which give them their characteristic scents.

4. How are aromatic compounds different from aliphatic compounds?

Aromatic compounds and aliphatic compounds are two different types of organic compounds. Aromatic compounds have a ring of atoms with alternating single and double bonds, while aliphatic compounds do not have this ring structure. Additionally, aromatic compounds have a distinct odor, while aliphatic compounds do not. Aromatic compounds also have unique chemical properties, such as high stability and low reactivity, that set them apart from aliphatic compounds.

5. Are aromatic compounds harmful to human health?

The safety of aromatic compounds depends on the specific compound and its concentration. Some aromatic compounds, such as benzene, have been linked to health issues such as cancer. However, many aromatic compounds are found in natural substances and are not harmful to human health. It is important to use aromatic compounds in moderation and follow safety guidelines when handling them.

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