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Phenyl group

December 15, 2023

In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6H5, and is often represented by the symbol Ph. 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.[1] Although often depicted with alternating double and single bonds, the phenyl group is chemically aromatic and has equal bond lengths between carbon atoms in the ring.[1][2]

Phenyl radical group

Nomenclature edit

Usually, a "phenyl group" is synonymous with C6H5− and is 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 center. 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 (C6H−5), the phenyl cation (C6H+5), and the phenyl radical (C
6H•
5).

Although Ph and phenyl uniquely denote C6H5−, substituted derivatives also are described using the phenyl terminology. For example, C6H4NO2− is nitrophenyl, and C6F5− 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 edit

Phenyl is derived from French phényle, which in turn derived from Greek φαίνω (phaino) 'shining', as the first phenyl compounds named were byproducts of making and refining various gases used for lighting.[3] According to McMurry, "The word is derived from Greek pheno 'I 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."[4]

Structure, bonding, and characterization edit

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. It is generally considered an inductively withdrawing group (-I), because of the higher electronegativity of sp2 carbon atoms, and a resonance donating group (+M), due to the ability of its π system to donate electron density when conjugation is possible.[5] 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.[6]

In 1H-NMR spectroscopy, protons of a phenyl group typically have chemical shifts around 7.27 ppm. These chemical shifts are influenced by aromatic ring current and may change depending on substituents.

Preparation, occurrence, and applications edit

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 are attacked by benzene to give phenyl derivatives:

 

where E+ (the "electrophile") = Cl+, NO+2, 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.[7]

References edit

  1. ^ a b March, Jerry (1992). Advanced organic chemistry: reactions, mechanisms, and structure (4th ed.). New York: Wiley. ISBN 978-0-471-60180-7.
  2. ^ a b "Aromaticity. Benzene and Other Aromatic Compounds". Virtual Textbook of Organic Chemistry. Michigan State University.
  3. ^ . English by Lexico Dictionaries. Archived from the original on February 16, 2013. Retrieved 24 July 2019.
  4. ^ McMurry, John E. (2009). Organic Chemistry, Enhanced Edition. Cengage Learning. p. 518. ISBN 9781111790042.
  5. ^ Hansch, Corwin.; Leo, A.; Taft, R. W. (1991-03-01). "A survey of Hammett substituent constants and resonance and field parameters". Chemical Reviews. 91 (2): 165–195. doi:10.1021/cr00002a004. ISSN 0009-2665.
  6. ^ Hameka, Hendrik F. (1987). "Computation of the structures of the phenyl and benzyl radicals with the UHF method". The Journal of Organic Chemistry. 52 (22): 5025–5026. doi:10.1021/jo00231a035. ISSN 0022-3263.
  7. ^ Silva, Pedro Jorge (2009). "Inductive and Resonance Effects on the Acidities of Phenol, Enols, and Carbonyl α-Hydrogens". The Journal of Organic Chemistry. 74 (2): 914–916. doi:10.1021/jo8018736. hdl:10284/3294. ISSN 0022-3263. PMID 19053615.

External links edit

  •   Media related to Phenyl group at Wikimedia Commons

December 15, 2023
phenyl, group, organic, chemistry, phenyl, group, phenyl, ring, cyclic, group, atoms, with, formula, c6h5, often, represented, symbol, phenyl, group, closely, related, benzene, viewed, benzene, ring, minus, hydrogen, which, replaced, some, other, element, comp. In organic chemistry the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5 and is often represented by the symbol Ph 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 1 Although often depicted with alternating double and single bonds the phenyl group is chemically aromatic and has equal bond lengths between carbon atoms in the ring 1 2 Phenyl radical group Contents 1 Nomenclature 1 1 Etymology 2 Structure bonding and characterization 3 Preparation occurrence and applications 4 References 5 External linksNomenclature editUsually a phenyl group is synonymous with C6H5 and is represented by the symbol Ph or archaically F 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 center 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 C6H 5 the phenyl cation C6H 5 and the phenyl radical C6 H 5 Although Ph and phenyl uniquely denote C6H5 substituted derivatives also are described using the phenyl terminology For example C6H4NO2 is nitrophenyl and C6F5 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 edit Phenyl is derived from French phenyle which in turn derived from Greek fainw phaino shining as the first phenyl compounds named were byproducts of making and refining various gases used for lighting 3 According to McMurry The word is derived from Greek pheno I 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 4 Structure bonding and characterization editPhenyl 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 It is generally considered an inductively withdrawing group I because of the higher electronegativity of sp2 carbon atoms and a resonance donating group M due to the ability of its p system to donate electron density when conjugation is possible 5 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 A 6 In 1H NMR spectroscopy protons of a phenyl group typically have chemical shifts around 7 27 ppm These chemical shifts are influenced by aromatic ring current and may change depending on substituents Preparation occurrence and applications editPhenyl 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 are attacked by benzene to give phenyl derivatives C 6 H 6 E C 6 H 5 E H displaystyle ce C6H6 E gt C6H5E H nbsp where E the electrophile Cl NO 2 SO3 These reactions are called electrophilic aromatic substitutions Representative compounds containing phenyl groups nbsp Atorvastatin Lipitor a blockbuster drug featuring two phenyl and one p fluorophenyl groups It is used to lower cholesterol in people with hypercholesterolaemia nbsp Fexofenadine Allegra Telfast another blockbuster drug which features a diphenylmethyl group as well as a p phenylene C6H4 group It is an antihistamine used to treat allergies nbsp Phenylalanine a common amino acid nbsp Biphenyl consisting of two phenyl groups The two rings tend not to be coplanar nbsp Chlorobenzene or phenyl chloride a solvent 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 7 References edit a b March Jerry 1992 Advanced organic chemistry reactions mechanisms and structure 4th ed New York Wiley ISBN 978 0 471 60180 7 a b Aromaticity Benzene and Other Aromatic Compounds Virtual Textbook of Organic Chemistry Michigan State University phenyl English by Lexico Dictionaries Archived from the original on February 16 2013 Retrieved 24 July 2019 McMurry John E 2009 Organic Chemistry Enhanced Edition Cengage Learning p 518 ISBN 9781111790042 Hansch Corwin Leo A Taft R W 1991 03 01 A survey of Hammett substituent constants and resonance and field parameters Chemical Reviews 91 2 165 195 doi 10 1021 cr00002a004 ISSN 0009 2665 Hameka Hendrik F 1987 Computation of the structures of the phenyl and benzyl radicals with the UHF method The Journal of Organic Chemistry 52 22 5025 5026 doi 10 1021 jo00231a035 ISSN 0022 3263 Silva Pedro Jorge 2009 Inductive and Resonance Effects on the Acidities of Phenol Enols and Carbonyl a Hydrogens The Journal of Organic Chemistry 74 2 914 916 doi 10 1021 jo8018736 hdl 10284 3294 ISSN 0022 3263 PMID 19053615 External links edit nbsp Media related to Phenyl group at Wikimedia Commons Retrieved from https en wikipedia org w index php title Phenyl group amp oldid 1180230098, wikipedia, wiki, book, books, library,

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