Intra-molecular selectivity of muonium towards chlorinated aromatic compounds

Muon resonance studies show that muonium atoms (Mu) in ethanol add selectively to certain C-sites of aromatic compounds containing -Cl and -OH substituents. The sites chosen seem to be those carrying the lowest electron density. This helps to characterize Mu as a nucleophile in addition reactions and, in this respect, Mu differs from ordinary H-atoms.The study shows no apparentinter-molecular selectivity between a pair of aromatic solutes in an equimolar mixture, but strongintra-molecular selectivity in an ether composed of those two aromatic rings. This difference between intra- and inter-molecular selectivity is interpreted as kinetic in origin — arising from the caging effect of the solvent and peculiar to reactions close to the diffusion-controlled limit.