Question

Which of the following pairs of aryl halides cannot be prepared directly by electrophilic substitution?

पर्याय

• Aryl chloride and aryl bromide

• Aryl fluoride and aryl chloride

• Aryl bromide and aryl iodide

• Aryl iodide and aryl fluoride

Answer 1

Aryl iodide and aryl fluoride

Explanation:

Because the reaction with iodine is reversible in nature, an oxidising agent (HNO₃, HlO₄) is required to oxidise the HI produced, aryl iodide and aryl fluoride cannot be synthesised directly by electrophilic substitution. Due to fluorine's extreme reactivity, this process cannot be used to make fluoro compounds.

\[\ce{Aryl iodide + aryl fluoride -> no reaction}\]