$$ \therefore $$ IUPAC name is trans-2-chloro-3-iodo-2-pentene.

Electron withdrawing group like -NO₂ facilitates nucleophilic substitution reaction in chlorobenzene.

In case of Lassaigne’s test of halogens, it is necessary to remove NaCN and Na₂S from the sodium extract, if nitrogen and sulphur are present. This is done by boiling the sodium extract with conc. HNO₃.

NaCN + HNO₃ $$ \to $$ NaNO₃ + HCN $$ \uparrow $$

Na₂S + 2HNO₃ $$ \to $$ 2NaNO₃ + H₂S $$ \uparrow $$

Because of high electronegativities of the halogen atom, the carbon halogen (C – X) is highly polarised covalent bond. Thus, the carbon atom of the C – X bond becomes a good site for attack by nucleophiles (electron rich species). Nucleophilic substitution reactions are the most common reactions of alkyl halides.