Abstract: The computational chemistry (Hartree-Fock, 3-21G basis) method was employed to obtain theoretical parameters of C-H bond dissociation energies and C-H bond lengths of unsaturated fatty acid methyl esters (UFAME), and then the relationship between molecular structures of unsaturated FAME and its oxidation deterioration characteristics were elucidated. Methyl oleate and methyl linoleate were used as models. The results show that the allylichydrogens(α-CH2), close to the double bond of the mode molecule, especially the α-CH2 with bis-allylichydrogens are the easy position for dehydrogenation, and the dehydrogenation at double bond (-CH=CH-) are the most difficult to occur. By analysis of the structure and composition changes of UFAME molecules in the oxidation process through FTIR and UV analysis, it is suggested that the oxidation deterioration of UFAME follows the principles of resonance effect of the radical, i.e. oxidation→resonance→double bond shift→isomerization.

Key words: unsaturated fatty acid methyl ester, computational chemistry, spectroscopy annalysis, oxidation deterioration characteristics, resonancestructure theory