Which among the following halide/s will not show ${\mathrm{S}}_{\mathrm{N}}1$ reaction:

Vinylic halides are organic compounds containing their halogen atom bonded to one of the two carbon atoms in the double bond present in that molecule.

Vinyl halide will not show ${\mathrm{S}}_{\mathrm{N}}1$ reaction, due to very
less stability of carbocation formed and partial
double bond character in C — Cl bond.

Since ${\mathrm{CH}}_3-\mathrm{CH}=\stackrel{+}{\mathrm{C}}\mathrm{H}$ is very unstable, ${\mathrm{CH}}_3-\mathrm{CH}=$ $\mathrm{CH}-\mathrm{Cl}$ cannot give ${\mathrm{S}}_{\mathrm{N}}1$ reaction.

Hence, the answer is B.