Chemistry - GOC Question with Solution | TestHub

$\mathrm{Cl}$ leaves as $\mathrm{C}{\mathrm{l}}^{-}$ because the cation formed is the methyl-substituted tropylium ion, with 6 π electrons (3 $\mathrm{C}=\mathrm{C}$) and an empty p orbital on the $\mathrm{s}{\mathrm{p}}^2$ carbon, so it is aromatic. Loss of $\mathrm{C}{\mathrm{l}}^{+}$ would give a carbanion with 8 π electrons, which is not stable.