FERMI RESONANCE IN SUBSTITUTED Z-3-METHYLENE PHTHALIDES

The absorption bands of the C=O Stretching vibrations of a series of t hirty-nine substituted Z-3-methylene phthalides (1a-s, 2a-h, 3a-f, 4a- c, and 5a-c) were measured in CHCl3 and CCl4. The two-level Fermi reso nance effect on the infrared spectra of the above compounds was invest igated after deconvolution and band separation. The wave numbers of th e unperturbed fundamental C=O stretching vibrations exhibit excellent linear correlations with Hammet's constants of substituents and C-13 N MR chemical shifts of the C=O group.