Tracking the chemistry of unsaturated [C.sub.3][H.sub.3] groups adsorbed on a silver surface: propargyl-allenyl-acetylide triple bond migration, self-hydrogenation, and carbon-carbon bond formation

Propargyl bromide (Br-C[H.sub.2]C=CH) was used as a precursor to generate [C.sub.3][H.sub.3] fragments on Ag(111) surface under ultrahigh vacuum conditions to understand the bonding and reactivity of [C.sub.3] species which include propargyl (M-C[H.sub.2]C=CH), allenyl (M-CH=C-C[H.sub.2]), and acetylide (M-C=CC[H.sub.3]) forms. The results showed that [1,3]-hydrogen shifts and [1,3]-sigmatropic rearrangement play mechanistically significant role in [C.sub.3][H.sub.3] heterogeneous model system.