Editing Phenyl group

{{Short description|Cyclic chemical group (–C₆H₅)}}
[[File:Phenyl_group.svg|thumb|140px|Phenyl radical group]]

In [[organic chemistry]], the '''phenyl group''', or '''phenyl ring''', is a [[cyclic compound|cyclic]] group of atoms with the formula {{chem|C6H5}}, and is often represented by the symbol '''Ph''' (archaically '''φ''') or '''Ø'''. The phenyl group is closely related to [[benzene]] and can be viewed as a benzene ring, minus a hydrogen, which may be replaced by some other element or compound to serve as a [[functional group]]. A phenyl group has 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]].<ref name=March>{{cite book |last=March |first=Jerry |title=Advanced organic chemistry: reactions, mechanisms, and structure |url=https://archive.org/details/advancedorganicc04edmarc |url-access=registration |date=1992 |publisher=Wiley |location=New York |isbn=978-0-471-60180-7 |edition=4th}}</ref> Although often depicted with alternating double and single bonds, the phenyl group is [[aromaticity|chemically aromatic]] and has equal bond lengths between carbon atoms in the ring.<ref name=March/><ref name="MSU">{{cite web |work=Virtual Textbook of Organic Chemistry |title=Aromaticity. Benzene and Other Aromatic Compounds |publisher=Michigan State University |url=http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/react3.htm}}</ref>

==Nomenclature==
Usually, a "phenyl group" is synonymous with {{chem2|C6H5\s}} and is [[skeletal formula#Pseudoelement symbols|represented by the symbol]] Ph (archaically, [[Φ]]), or Ø. Benzene is sometimes denoted as PhH. Phenyl groups are generally attached to other atoms or groups. For example, [[triphenylmethane]] ({{chem2|Ph3CH}}) has three phenyl groups attached to the same carbon center. Many or even most phenyl compounds are not described with the term "phenyl". For example, the chloro derivative {{chem2|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 ({{chem2|C6H5-}}), the phenyl cation ({{chem2|C6H5+}}), and the phenyl [[radical (chemistry)|radical]] ({{chem|C|6|H|5|•}}).

Although Ph and phenyl uniquely denote {{chem2|C6H5\s}}, substituted derivatives also are described using the phenyl terminology. For example, {{chem2|C6H4NO2\s}} is nitrophenyl, and {{chem2|C6F5\s}} is pentafluorophenyl. Monosubstituted phenyl groups (that is, disubstituted benzenes) are associated with [[electrophilic aromatic substitution]] reactions and the products follow the [[arene substitution pattern]]. So, a given substituted phenyl compound has three isomers, ''ortho'' (1,2-disubstitution), ''meta'' (1,3-disubstitution) and ''para'' (1,4-disubstitution). A disubstituted phenyl compound (trisubstituted benzene) may be, for example, 1,3,5-trisubstituted or 1,2,3-trisubstituted. Higher degrees of substitution, of which the pentafluorophenyl group is an example, exist and are named according to IUPAC nomenclature.

===Etymology===
Phenyl is derived {{ety|fr|phényle}}, which in turn derived {{ety|el|''φαίνω'' (phaino)|shining}}, as the first phenyl compounds named were byproducts of [[history of manufactured gas|making and refining]] various [[gas lighting|gases used for lighting]].<ref>{{cite web |url=http://www.oxforddictionaries.com/us/definition/american_english/phenyl |archive-url=https://web.archive.org/web/20130216194714/http://oxforddictionaries.com/us/definition/american_english/phenyl |url-status=dead |archive-date=February 16, 2013 |title=phenyl |work=English by Lexico Dictionaries |access-date=24 July 2019}}</ref> According to McMurry, "The word is derived {{ety|el|pheno|I&nbsp;bear light}}, commemorating the discovery of benzene by [[Michael Faraday]] in 1825 from the oily residue left by the illuminating gas used in London street lamps."<ref>{{cite book |last1=McMurry |first1=John E. |title=Organic Chemistry, Enhanced Edition |date=2009 |publisher=Cengage Learning |isbn=9781111790042 |page=518 |url=https://books.google.com/books?id=Ffs7AAAAQBAJ |language=en}}</ref>

==Structure, bonding, and characterization==
Phenyl compounds are derived from [[benzene]] ({{chem2|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]]. It is generally considered an inductively withdrawing group (-''I''), because of the higher electronegativity of sp<sup>2</sup> carbon atoms, and a resonance donating group (+''M''), due to the ability of its π system to donate electron density when conjugation is possible.<ref>{{Cite journal|last=Hansch|first=Corwin.|last2=Leo|first2=A.|last3=Taft|first3=R. W.|date=1991-03-01|title=A survey of Hammett substituent constants and resonance and field parameters|journal=Chemical Reviews|volume=91|issue=2|pages=165–195|doi=10.1021/cr00002a004|issn=0009-2665}}</ref> 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 orbital theory|molecular orbitals]].<ref name="MSU"/>

The bond lengths between carbon atoms in a phenyl group are approximately 1.4&nbsp;[[Ångström|Å]].<ref name="Hameka1987">{{cite journal|last1=Hameka|first1=Hendrik F.|title=Computation of the structures of the phenyl and benzyl radicals with the UHF method|journal=The Journal of Organic Chemistry|volume=52|issue=22|year=1987|pages=5025–5026|issn=0022-3263|doi=10.1021/jo00231a035}}</ref>

In <sup>1</sup>H-[[nuclear magnetic resonance|NMR]] spectroscopy, protons of a phenyl group typically have [[chemical shift]]s around 7.27 ppm. These chemical shifts are influenced by [[aromatic ring current]] and 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]] ({{chem2|C6H5Li}}) and [[phenylmagnesium bromide]] ({{chem2|C6H5MgBr}}). Electrophiles are attacked by benzene to give phenyl derivatives:
:<chem>C6H6 + E+ -> C6H5E + H+</chem>
where {{chem2|E+}} (the "electrophile") = {{chem2|Cl+, NO2+, SO3}}. These reactions are called [[electrophilic aromatic substitution]]s.
<gallery caption="Representative compounds containing phenyl groups" widths="180px" heights="120px" perrow="5">
File: Atorvastatin.svg|[[Atorvastatin|Atorvastatin (Lipitor)]], a [[Pharmaceutical drug#Blockbuster drug|blockbuster drug]] featuring two phenyl and one ''p''-fluorophenyl groups. It is used to lower cholesterol in people with [[hypercholesterolaemia]].
File: Fexofenadine2DCSD.svg|[[Fexofenadine|Fexofenadine (Allegra, Telfast)]], another blockbuster drug, which features a diphenylmethyl group as well as a ''p''-[[phenylene]] ({{chem2|C6H4}}) group. It is an [[antihistamine]] used to treat [[allergies]].
File: Phenylalanin_-_Phenylalanine.svg|[[Phenylalanine]], a common amino acid.
File: Bifenyl.svg|[[Biphenyl]], consisting of two phenyl groups. The two rings tend not to be coplanar.
File: Chlorobenzene2.svg|[[Chlorobenzene]] (or phenyl chloride), a solvent.
</gallery>

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 "[[Benzene#Production|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]], {{chem2|C6H5OH}}. It is often said the [[resonance (chemistry)|resonance stability]] of phenol makes it a stronger [[acid]] than that of [[aliphatic]] [[alcohols]] such as [[ethanol]] ([[acid dissociation constant|p''K''<sub>a</sub>]] = 10 vs. 16–18). However, a significant contribution is the greater [[electronegativity]] of the ''sp''<sup>2</sup> [[alpha carbon]] in phenol compared to the ''sp''<sup>3</sup> alpha carbon in aliphatic alcohols.<ref name="Silva2009">{{cite journal|last1=Silva|first1=Pedro Jorge|title=Inductive and Resonance Effects on the Acidities of Phenol, Enols, and Carbonyl α-Hydrogens|journal=The Journal of Organic Chemistry|volume=74|issue=2|year=2009|pages=914–916|issn=0022-3263|doi=10.1021/jo8018736|pmid=19053615|hdl=10284/3294|hdl-access=free}}</ref>

==References==
{{Reflist}}

==External links==
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[[Category:Aryl groups]]
[[Category:Phenyl compounds| ]]