benzyn

Benzyn is a term sometimes used to refer to benzyne, a highly reactive intermediate in aromatic chemistry. Benzyne, also known as aryne, is a dehydrobenzene species that contains a formal triple bond between two adjacent carbon atoms in the benzene ring. This transient intermediate is not isolated under normal conditions but generated in situ during chemical reactions.

In benzyne, the two adjacent ring carbons are sp-hybridized, giving a carbon–carbon triple bond that short-circuits part of the aromatic sextet. The molecule behaves as an aryne, undergoing rapid cycloaddition or nucleophilic capture, leading to a variety of substituted aromatic products.

Benzyne is typically produced by elimination reactions on ortho-disubstituted arenes. Common routes include elimination of adjacent halide and leaving group from o-dihalobenzenes using strong bases such as sodium amide in liquid ammonia, or metal–halogen exchange followed by elimination. Other approaches include thermal or fluoride-induced decomposition of suitable precursors.

Benzyne readily participates in cycloaddition with dienes (Diels–Alder) or with nucleophiles to form substituted benzenes. The aryne intermediate can be trapped by various partners, enabling rapid construction of polysubstituted arenes. Regioselectivity is governed by substituents on the precursor and reaction conditions.

Because benzyne chemistry enables rapid assembly of complex aromatic frameworks, it is used in organic synthesis for creating polycyclic aromatic compounds and for diversification of drug-like molecules.

Benzyne is highly reactive and not isolable; reactions are conducted under carefully controlled conditions to avoid uncontrolled side reactions.

See also: aryne chemistry; benzyne synthesis; Diels–Alder reactions.