In the presence of silica, a number of aromatic hydrocarbons such as toluene, o-, m-, and p- xylene, anthracene and phenol are brominated by Br 2 under mild conditions; for example Br 2/SiO 2 brominates naphthalene readily at 25° C to 1-bromonaphthalene. For comparison, we have also brominated all of the substrates in with bromine in the absence of silica gel.
