Phenyl group

A phenyl group is a benzene ring with one hydrogen atom removed, leaving a substituent that can bond to another atom or group.

Benzene: A six-carbon aromatic hydrocarbon with a ring of delocalized electrons and formula C₆H₆. Removing one hydrogen from this ring produces the phenyl group.
Electrophilic aromatic substitution: A reaction in which an electrophile replaces a hydrogen on an aromatic ring while aromaticity is restored. A phenyl ring can undergo this characteristic reaction when it has a replaceable ring hydrogen.
Polystyrene: A synthetic polymer whose repeating units contain phenyl-substituted carbon backbones. Its pendant phenyl groups contribute to the polymer’s rigidity and characteristic properties.
Benzyl group: A substituent consisting of a phenyl ring connected through a methylene group, written C₆H₅CH₂–. Unlike phenyl, benzyl attaches to the rest of a molecule through an intervening carbon.
Aromaticity: The unusual stability associated with cyclic, conjugated molecules whose electrons are delocalized around a ring. Phenyl retains benzene’s aromatic electron system after losing a hydrogen.
Inductive effect: The transmission of electron density through sigma bonds because of differences in electronegativity. A phenyl substituent can influence nearby atoms through its sigma-bond framework.
Aspirin: A drug also called acetylsalicylic acid, used to relieve pain, fever, and inflammation. Its aromatic ring is part of a substituted phenyl framework.
Cyclohexyl group: A substituent derived from cyclohexane by removing one hydrogen atom. Cyclohexyl has a saturated six-membered ring rather than phenyl’s aromatic ring.
Aryl group: A substituent derived from an aromatic ring by removing one hydrogen atom. Phenyl is the simplest and most familiar aryl group.
Resonance effect: An electronic effect caused by delocalization through overlapping p orbitals in a conjugated system. Conjugation with phenyl can redistribute electron density when the attachment permits orbital overlap.

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