Aryl

Aryl is a term used in organic chemistry to describe a functional group or substituent derived from an aromatic ring, such as a benzene ring, but missing one hydrogen atom. The aryl group is represented by the symbol Ar. Aryl groups are distinct from alkyl groups, which are derived from alkanes and contain only single bonds.

Structure and Properties

Aryl groups, like the phenyl group (C6H5), derived from benzene by removing one hydrogen atom, are characterized by their aromatic properties. These properties include a high degree of chemical stability and a tendency to undergo electrophilic substitution reactions rather than addition reactions. The stability comes from the aromatic ring's ability to delocalize electrons across its pi system.

Common Aryl Groups

Some common aryl groups include:

• Phenyl group (C6H5-) - derived from benzene
• Tolyl group (C6H4CH3-) - derived from toluene
• Naphthyl group (C10H7-) - derived from naphthalene

Reactions Involving Aryl Groups

Aryl groups participate in various types of chemical reactions:

• Arylation: The introduction of an aryl group into a molecule.
• Suzuki coupling: A cross-coupling reaction used to synthesize biaryl compounds, involving an aryl boronic acid and an aryl halide.
• Friedel-Crafts alkylation/acylation: A reaction where an aryl group is introduced into an aromatic compound using an alkyl or acyl halide in the presence of a Lewis acid catalyst.

Applications

Aryl groups are fundamental in the synthesis of a wide range of chemical compounds, including pharmaceuticals, dyes, plastics, and agrochemicals. Their ability to stabilize charge through resonance makes them key intermediates in many organic synthesis reactions.

See Also

• Aromaticity
• Functional group
• Organic synthesis