The vibrational spectra of (HCC)2CO and (NC)2CO

Abstract Infrared and Raman spectra are reported for diethynyl ketone, (HCC) 2 CO and for carbonyl cyanide, (NC) 2 CO. Both are planar C 2 v molecules. Assignments are made for all 18 fundamentals of the former, and for all 12 of the latter. All but two or three for each molecule are established beyond any doubt.