Question

Rank the four aromatic rings below by reactivity (least reactive to most reactive) when mixed with the following benzenediazonium ion

Answer 1

The Diazonium salt give coupling reaction with any substituted benzene from their ortho and para position, so if the subsumed benzene has ortho para directing group is attached reaction proceed faster NEN: HH OCH Diazonium sal Methoxybenzene N N: H CH3 CH3 Diazonium salt Toluene Br Diazonium salt Bromobenzene NO2 NEN: hH Diazonium salt Nitrobenzemne The nitro group is electron withdrawing group, so it can abstract pi-electrons from benzene ring and make ring electron deficient, so reactivity of nitrobenzene is least, as follows : O :O O: 0:

Nitrobenzne The methoxy group is an electron releasing group and it can donate pi electron from oxygen atom towards benzene ring ant make ring as electron rich, so ring carry pi-electrons at ortho and para position that's why the coupling take place easily: OMe OMe OMe Methoxybenzene The halogens are ortho para deactivator and directing group because of their electronegativity they also make electron deficient but not much more like nitro and other electron withdrawing groups CH3 Br Bromobenzene Toluene The methyl group is also ortho para activating and work as an inductive effect donor that can make ring electron rich, So, reactivity of ring is greater than aryl halide and nitro benzene but less than methoxybenzene. Hence, the order of reactivity towards diazonium coupling from least reactive to most reactive is, as follows CH3 OMe Br NO

Answer 2

The Diazonium salt give coupling reaction with any substituted benzene from their ortho and para position, so if the subsumed benzene has ortho para directing group is attached reaction proceed faster. The nitro group is electron withdrawing group, so it can abstract pi-electrons from benzene ring and make ring electron deficient, so reactivity of nitrobenzene is least, as follows: The methoxy group is an electron releasing group and it can donate pi electron from oxygen atom towards benzene ring ant make ring as electron rich, so ring carry pi-electrons at ortho and pan position that's why the coupling take place easily: The halogens are ortho para deactivator and directing group because of their electronegativity they also make electron deficient but not much more like intro and other electron withdrawing groups. The methyl group is also ortho para activating and work as an inductive effect donor that can make ring electron rich, So, reactivity of ring is greater than aryl halide