Evidence for the existence of cycloalkynes as strained as cyclopent yne'and norbornyne2 has been available for several years. Attempts to generate strained acetylenes such as cyclob~ tyne'-~ and acenaphthyne4 have been unsuccessful. The observed products in the latter two cases can be rationalized without recourse to the free acetylene. We now wish to report the synthesis, spectroscopic characterization, and chemistry of acenaphthyne, the ...