Microwave Spectra of 13C‐ and 18O‐Containing Species and the Structure of Vinylene Carbonate

The microwave spectra of two 13C and two 18O species of vinylene carbonate have been analyzed. The spectra were observed with the isotopes present in natural abundance. An rs structure of the heavy atoms in the molecule shows a short C=O bond length of 1.1908 ± 0.0006 A with the other bonds being of approximately the expected length. The ring angles are nearly equal with two bonds at the carbon atoms making angles of 108°40′ ± 9′ and 108°40′ ± 40′ and the angle at the oxygen atom being 106°56′ ± 24′.