vinylidene

Vinylidene is a term used in chemistry to refer to two related concepts involving a two-carbon fragment derived from ethene. In organic chemistry, the vinylidene group denotes the structure CH2=C-, a methylene-bearing carbon double-bonded to a second carbon that carries substituents. This fragment appears in various substituted alkenes and in the names of certain dichloro- and difluorinated compounds. Notable examples include vinylidene chloride (CH2=CCl2) and vinylidene difluoride (CH2=C(F)2). Compounds containing the vinylidene fragment can serve as monomers or intermediates in polymer chemistry; polyvinylidene difluoride (PVDF) is derived from vinylidene difluoride and is valued for chemical resistance and mechanical properties.

In organometallic chemistry, vinylidene refers to a class of metal complexes in which a vinylidene ligand forms a double bond to a metal, producing a M=C–C fragment. These species are related to carbenes and alkylidenes and can participate in various transformations, including rearrangements and catalytic processes. The vinylidene fragment may arise from rearrangements of precursors such as alkynes or alkenes and can act as a reactive intermediate in catalytic cycles.

Etymology: the term combines “vinyl” with “idene,” reflecting the vinylidene fragment’s structure originating from the vinyl group. The concept encompasses both simple organic substituents and more complex metal-bound species encountered in synthesis and catalysis.