Question

The reaction of N-bromosuccinimide with the following compounds has been reported in the chemical literature. Each compound yields a single product in 95% yield. Identify the product formed from each starting material. p-tert-Butyltoluene 4-Methyl-3-nitroanisole Sample Solution The only benzylic hydrogens in p-tert-butyltoluene are those of the methyl group that is attached directly to the ring. Substitution occurs there to give p-tert-butylbenzyl bromide

Answer 1

the substitution of allylic and benzylic hydrogens. These reactions are carried out in CCl as the solvent and a radical initiator (generally peroxides)

When NBS is added to p-tert-Butyltoluene, free-radical bromination takes place at the benzylic position resulting in the formation of 1-(bromomethyl)4-(tert-butyl) In this reactant, the benzylic hydrogens are the methyl hydrogens that are directly attached to the aromatic ring The reaction is as follows: CH3 CH3 CCl4,80°C free-radical H3C-C- CH2 H3C-C CH3 CH3 CH3 nitiator p-tert-Butyltoluene 1-(bromomethyl)-4-(ter-butyl)benzene NBS Succimanide

When NBS is added to 4-methyl-3-nitroanisole, free-radical bromination takes place at the benzylic position resulting in the formation of 1-bromomethyl-4-methoxy-2-nitrobenzene. In this reactant, the benzylic hydrogens are the methyl hydrogens that are directly attached to the aromatic ring.

The reaction is as follows 0 NO2 NO2 CCla, 80°C + Br-N/ | free.adca. CH2 Br 0% CH3 HyC-0 initiator 1-Bromomethyl-4-methoxy-2 nitro-benzene 4-Methyl-3-nitroanisole NBS HN 0 Succinamide