Gas-phase methylation of phenol and anisole by dimethylhalonium ions

Reactions of Me2X+ (X = F, Cl, Br), prepd. by dil. gas-phase γ-radiolysis of MeX, with PhOH and PhOMe were examd. at 100-760 Torr in the presence of NH3(g) and in the presence and absence of C6H6. PhOH was selectively methylated at the O atom under kinetic-control conditions [high MeX pressure, NH3(g)]. Both PhOH and PhOMe underwent ring methylation preferentially at the ortho and para positions; ortho attack was favored by low MeX pressure and the absence of NH3(g). PhOH reacted with Me2X faster than did C6H6. These results are discussed in terms of kinetically preferred attack on the O atom of PhOH and PhOMe.