The reactions of ground-state atomic carbon with acetylene, (1), methylacetylene, (2), 22 3 ethylene, (3), and propylene, (4), are investigated at relative collision energies between 8.8 24 36 and 45 kJ mol~1 in crossed-beam experiments to elucidate the reaction products and chemical dynamics of atom-neutral encounters relevant to the formation of carbon-bearing molecules in the interstellar me...