Main Difference – Aryl vs Phenyl
Phenyl and aryl are two chemical terms used to name functional groups of organic compounds. An aryl group always contains an aromatic ring. Aryl group is a simple aromatic compound where one hydrogen atoms is removed, allowing it to get attached to a carbon chain. Phenyl is the name given to a side group. It is composed of a benzene ring which is missing a hydrogen atom. The phenyl group can get attached to a vacant point as a side group of a molecule. The main difference between aryl and phenyl group is that the term aryl group is used to name any aromatic functional group whereas the term phenyl is used to name the functional group derived from a benzene ring.
Key Areas Covered
1. What is Aryl
– Definition, Examples, Aryl Halides
2. What is Phenyl
– Definition, Structure, Examples
3. What is the Difference Between Aryl and Phenyl
– Comparison of Key Differences
Key Terms: Aromatic, Aryl, Aryl Halide, Benzene, Functional Group, Hybridization, Naphthyl, Phenyl
What is Aryl
An aryl group always contains an aromatic ring. Aryl group is a simple aromatic compound where one hydrogen atom is removed from the ring, allowing it to get attached to a carbon chain. The most common aromatic ring is benzene. All aryl groups are derived from benzene structures.
Some examples of aryl groups are phenyl group derived from benzene and naphthyl group derived from naphthalene. These aryl groups can have substitutions in their aromatic structure. For example, tolyl group is derived from toluene; toluene is a benzene ring with the substitution of a methyl group. All aryl groups are unsaturated. This means the structure of aryl groups are composed of double bonds. But benzene is not the only type of aromatic ring that aryl groups can have. For example, indolyl group is an aryl group attached to the common amino acid, tryptophan. The following image shows the phenyl group which is derived from a benzene ring.
Figure 1: Groups in Blue are Naphthyl Groups
An aryl halide is a molecule having a halogen atom attached to a sp2 hybridized carbon in an aromatic ring directly. This is an unsaturated structure due to the presence of double bonds in the aromatic ring. Aryl halides also show the dipole-dipole interactions. The carbon-halogen bond is stronger than that of alkyl halides due to the presence of ring electrons. This is because the aromatic ring gives electrons to the carbon atom, so its positive charge is somewhat reduced. Aryl halides can undergo electrophilic substitution and can get alkyl groups attached to the ortho, para or meta positions of the aromatic ring. One or two halogens can get attached to the aromatic ring. This is also in ortho, para or meta positions.
What is Phenyl
Phenyl is the chemical structure which has a benzene ring lacking a hydrogen atom. Since it lacks a hydrogen atom, there is a vacant point for other atoms or molecules to get attached to the phenyl group. The chemical formula of phenyl is C6H5. The phenyl group is a cyclic structure that has a planar geometry. Here, five carbon atoms are bonded to five hydrogen atoms individually. The remaining carbon atom has no hydrogen atom bonded to it.
Figure 2: Groups in Blue are Phenyl Groups
Phenyl group is more stable when compared to the corresponding aliphatic alkyl group. This is due to the stabilization of the aromatic ring via delocalization of pi electrons. Phenyl group alone is not stable because the carbon atom has an incomplete electron configuration due to the lack of a hydrogen atom to share an electron. This makes phenyl group very reactive. Phenyl group will react with an electron-rich atom or group of atoms.
Difference Between Aryl and Phenyl
Definition
Aryl: Aryl group always contains an aromatic ring.
Phenyl: Phenyl is the chemical structure derived from benzene by removal of one hydrogen atom
Formation
Aryl: An aryl group is formed when a hydrogen atom is lost from an aromatic group.
Phenyl: A phenyl group is formed when a hydrogen atom is removed from a benzene ring.
Carbon Atoms
Aryl: An aryl group can have different numbers of carbon atoms depending on the type of aryl group.
Phenyl: Phenyl group consist of six carbon atoms.
Examples
Aryl: Some examples of aryl groups include phenyl group, naphthyl group, toluyl group, indolyl group, etc.
Phenyl: Phenyl group is an individual group derived from a benzene ring.
Conclusion
Phenyl group is a type of aryl group. Aryl groups are functional groups present in organic compounds that are aromatic. The main difference between aryl and phenyl group is that, the term aryl group is used to name any aromatic functional group whereas the term phenyl is used to name the functional group derived from a benzene ring.
Reference:
1. “The Phenyl Group.” Chemistry LibreTexts, 21 July 2016, Available here.
2. Helmenstine, Anne Marie. “Aryl Group Definition in Chemistry.” ThoughtCo, Jun. 8, 2017, Available here.
Image Courtesy:
1. “Naphthyl Group V.1” By Jü – Own work (CC0) via Commons Wikimedia
2. “Phenyl Group General Formulae V.1” By Jü – Own work (CC0) via Commons Wikimedia
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