The structures of 1,2,4-trioxolanes (ozonides) (2a-2f) derived from mono-substituted alkenes (1a-1f), respectively, were determined by spectroscopic methods, such as H-1-nmr, C-13-nmr, ir, two-dimensional nmr, and mass spectra. The coupling constant of the geminal protons on the trioxolane ring is zero. This unusual coupling constant resulted from the electronegativity of two oxygen atoms near the geminal protons.