Vinylic

Vinylic describes structural features related to the vinyl group, typically the fragment –CH=CH2. A vinylic carbon is one that is part of a carbon–carbon double bond; vinylic hydrogens are those attached to these sp2 carbons. The term is used to distinguish atoms or substituents that are directly on the double bond from allylic positions, which are adjacent to the double bond but not part of it.

In practice, vinylic terminology appears in many organic compounds and in vinyl polymers. Common examples include vinyl chloride (CH2=CHCl), vinyl acetate (CH2=CHOC(O)CH3), and styrene (Ph–CH=CH2). The vinyl group enables polymerization, allowing many monomers to form long polymers such as polyvinyl chloride, polyvinyl acetate, and polystyrene. Reactivity at vinylic centers reflects the sp2 hybridization and the partial double-bond character of the C=C bond; substitutions at vinylic carbons differ from those at allylic or aliphatic carbons. Vinylic halides, for instance, tend to undergo elimination or radical reactions and are less amenable to straightforward SN2 substitution; vinyl cations are relatively unstable and not common intermediates.

In spectroscopy, materials science, and synthetic planning, vinylic designation helps describe functionalities and reaction pathways that involve the carbon–carbon double bond.