We report the thermochemistry of the stepwise hydration of the acetylene trimer ion (C2H2)(3)(+) using the drift tube technique. The binding energies and entropy changes for the addition of 1-7 water molecules to (C2H2)(3)(+) are identical to the corresponding values for the hydration of the benzene radical cation. The (C2H2)(3)(+) ion undergoes proton transfer within the (C2H2)(3)(+)(H2O)(n) clusters with n >= 4. The proton affinity (211 kcal/mol) of the radical generated by the deprotonation of the (C2H2)(3)(+) ion is similar to that of the phenyl radical (C6H5.). Thus, the formation of the benzene ion is further confirmed in the ionized acetylene clusters. (c) 2007 Elsevier B.V. All rights reserved.