World Library  
Flag as Inappropriate
Email this Article

Phenyl

Article Id: WHEBN0003135645
Reproduction Date:

Title: Phenyl  
Author: World Heritage Encyclopedia
Language: English
Subject: Epinephrine, Functional group, IUPAC nomenclature of organic chemistry, Nitrobenzene, Benzonitrile, Silicone resin, Carbyne, Boron trichloride, Pinacol rearrangement, Boronic acid
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Phenyl

Not to be confused with benzyl, benzoyl, or phenol.

In organic chemistry, the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the remaining carbon bonded to a substituent. Phenyl groups are commonplace in organic chemistry.[1] Although often depicted with alternating double and single bonds, phenyl groups are chemically aromatic and show nearly equal bond lengths between carbon atoms in the ring.[1][2]

Nomenclature

Phenyl groups often have the general formula CnHn represented by the symbol Ph or, archaically, Φ. Benzene is sometimes denoted as PhH. Phenyl groups are generally attached to other atoms or groups. For example, triphenylmethane (Ph3CH) has three phenyl groups attached to the same carbon centre. Many or even most phenyl compounds are not described with the term "phenyl". For example the chloro derivative C6H5Cl is normally called chlorobenzene, although it could be called phenyl chloride. In special (and rare) cases, isolated phenyl groups are detected: the phenyl anion (C6H5), the phenyl cation (C6H5+), and the phenyl radical (C6H5·).

Although Ph and phenyl uniquely denote C6H5, substituted derivatives also are described using the phenyl terminology. For example, O2NC6H4 is nitrophenyl (of which three isomers are possible) and F5C6 is pentafluorophenyl.

Structure, bonding, characterization

Phenyl compounds are derived from benzene (C6H6), at least conceptually and often in terms of their production. In terms of its electronic properties, the phenyl group is related to a vinyl group. The phenyl group is hydrophobic. Phenyl groups tend to resist oxidation and reduction. Phenyl groups (like all aromatic compounds) have enhanced stability in comparison to equivalent bonding in aliphatic (non-aromatic) groups. This increased stability is due to the unique properties of aromatic molecular orbitals.[2]

The bond lengths between carbon atoms in a phenyl group are approximately 1.4 Å (Ångström).[3]

In 1H-NMR spectroscopy, protons of a phenyl group typically absorb chemical shifts around 7.27 ppm. The position of these chemical shifts is influenced by aromatic ring current, and these values may change depending on substituents.

Preparation, occurrence, and applications

Phenyl groups are usually introduced using reagents that behave as sources of the phenyl anion or the phenyl cation. Representative reagents include phenyllithium (C6H5Li) and phenylmagnesium bromide (C6H5MgBr). Electrophiles attack benzene to give phenyl derivatives:

C6H6 + E+ → C6H5E + H+

where E+ (the "electrophile") = Cl+, NO2+, SO3. These reactions are called electrophilic aromatic substitutions.

Phenyl groups are found in many organic compounds, both natural and synthetic (see figure). Most common among natural products is the amino acid phenylalanine, which contains a phenyl group. A major product of the petrochemical industry is "BTX" consisting of benzene, toluene, and xylene - all of which are building blocks for phenyl compounds. The polymer polystyrene is derived from a phenyl-containing monomer and owes its properties to the rigidity and hydrophobicity of the phenyl groups. Many drugs as well as many pollutants contain phenyl rings.

One of the simplest phenyl-containing compounds is phenol, C6H5OH. It is often said the resonance stability of phenol makes it a stronger acid than that of aliphatic alcohols such as ethanol (pKa = 10 vs. 16–18). However, a significant contribution is the greater electronegativity of the sp2 alpha carbon in phenol compared to the sp3 alpha carbon in aliphatic alcohols.[4]

References

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.