Here we report the remarkable chemistry exhibited by 6-bromo-1-hexene on a Cu3Pt(lll) surface. The dehydrocyclization reaction leading to the formation of benzene takes place at very low coverage; as the surface fills up, decomposition becomes a predominant pathway. Further increase of the surface concentration of 6-bromo-1-hexene leads to the hydrogenation of 5-hexenyl formed on a surface as a result of C-Br bond dissociation. This reaction produces l-hexene, which is stable on the surface until the molecular desorption of this compound commences at 230 K. Molecular desorption of 6-bromo-1-hexene from the monolayer becomes significant at even higher exposures. All these processes occur very cleanly within a specific coverage range, making the 6-bromo-1-hexene on the Cu3Pt(111) surface extremely attractive for analysis of kinetics of coverage-dependent reactions. Steric requirements for each of the processes described here and the availability of the adsorption sites on the alloy surface are believed to govern the predominant reaction.