基于计算化学和波谱分析的不饱和脂肪酸甲酯氧化衰变特性研究

利用计算化学Hartree-Fock(HF)方法，在3-21G基组水平下，以C-H键解离能和 C-H键长为理论参数，从分子水平研究了影响不饱和脂肪酸甲酯氧化安定性的结构因素，计算结果表明，紧邻不饱和脂肪酸甲酯双键的α-CH2，尤其是具有双烯丙基结构的α-CH2，是不饱和脂肪酸甲酯氧化脱氢反应发生的位点，而双键上最难发生脱氢。结合傅里叶红外光谱和紫外可见光谱对不饱和脂肪酸甲酯在氧化过程中分子构型及化学组成的变化情况进行分析，结果表明，不饱和脂肪酸甲酯的氧化衰变遵循共振化结构理论，即氧化→共振→双键转移→异构化。

OXIDATION DETERIORATION CHARACTERISTICS OF UNSATURATED FATTY ACID METHYL ESTERS BASED ON COMPUTATIONAL CHEMISTRY AND SPECTROSCOPIC ANALYSIS

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.