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An organic compound containing a carbon-halogen bond. The bonding environment matters: a vinylic halide has the halogen directly attached to a double-bonded carbon, whereas an allylic halide has it attached to the adjacent saturated carbon.

The first product is $\mathrm{BrCH}=\mathrm{C}(\mathrm{C}{\mathrm{H}}_3)\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{OC}{\mathrm{H}}_3$, with the original alkene geometry retained. methoxide attacks the primary saturated carbon bearing bromine from the backside. Its oxygen lone pair forms the new C–O bond as the C–Br bonding pair leaves with bromide. The other bromine is vinylic, directly bonded to an sp${}^2$ carbon: ordinary SN2 reaction is unfavourable there, and ionization would require an unstable vinyl cation. Thus the primary alkyl bromide is replaced selectively, rather than replacing the vinylic halide or moving the double bond. There is no observable inversion label at the attacked carbon because it is a methylene.

The second product is sodium 4-propoxybutane-1-sulfonate, $\mathrm{N}{\mathrm{a}}^{+}{}^{-}{\mathrm{O}}_3\mathrm{S}(\mathrm{C}{\mathrm{H}}_2{)}_4\mathrm{OC}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$. sodium hydride first removes the alcohol proton, giving propoxide and hydrogen. The propoxide oxygen then attacks the primary ring carbon bonded to the ring oxygen; simultaneous cleavage of that carbon–oxygen bond opens the sultone. The departing ring oxygen remains attached to sulfur as part of the resonance-stabilized sulfonate anion. The carbon attached directly to sulfur is not the substitution site, because cleavage there would not expel the same stable sulfonate leaving group. This is carbon-centred ring opening of a cyclic sulfonate ester, not addition across an S=O bond.

Vinyl chloride is chloroethene, $\mathrm{C}{\mathrm{H}}_2=\mathrm{CHCl}$. It is a small vinylic halide whose carbon-carbon double bond can participate in addition polymerization.

Polymerization converts many vinyl chloride molecules into polyvinyl chloride, with chlorine-bearing repeating units along the carbon backbone. The resulting polymer has physical properties very different from those of the molecular monomer.

A vinylic halide has a halogen atom bonded directly to a carbon of a carbon-carbon double bond. Vinyl chloride is the simplest common example.

Ordinary substitution at a saturated carbon cannot be transferred unchanged to this geometry and bonding. The distinction between a vinylic halide and an allylic halide is therefore mechanistically useful, even when both molecules contain an alkene and a halogen.