Question

Rank the following compounds in order of increasing reactivity for electrophilic aromatic substitution. Explain your reasoning.

Answer 1

Methyl groups are electron donating.These kind of groups donates electron to the ring & thus electron density on the ring increases which Activates ring towards electrophillic reaction. Thus increase in electron donating groups increases electrophilicity of the ring.

Bromine groups are electron withdrawing.These kind of groups withdraws electron from the ring & thus electron density on the ring decreases which deactivates ring towards electrophillic reaction.And thus increase in such a electron withdrawing groups decreases electrophilicity of the ring.

Order is given below.

CH Br Bn CH Br CH Direction of electron flow CH Electron Donating groups Electron withdwawing groups