Selective functionalization of hydrocarbons with O and nitrenes (NR groups) is important in many aspects of chemical synthesis—from alternative fuel production to pharmaceutical applications. We have investigated the activity of Au for promoting selective functionalization processes because of the intense interest in Au-based catalysts. Reactions of styrene have been used to establish proof of principle and to illustrate that high selectivity for epoxidation and the analogous process, addition of NH to form the aziridines on Au(111). Fundamental studies of the surface reactivity and structure show that metastable phases of Au-O species are particularly active and selective. A combination of scanning tunneling microscopy, surface spectroscopy and reactivity measurements were used.