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采用傅里叶红外光谱技术研究了温度对于硬脂酸C-H伸缩振动、分子脂肪链构象改变和分子间作用力的影响。运用变温红外技术在293~393K范围内,分别测定了硬脂酸C-H的一维红外光谱、二阶导数红外光谱、四阶导数红外光谱和去卷积红外光谱。结果表明:1在293~333K范围内,一维红外光谱中2 965,2 870cm-1附近的弱吸收谱带分别归属于甲基的不对称伸缩振动模式νas(-CH3)和对称伸缩振动模式νs(-CH3),相应的导数光谱及去卷积红外光谱能提高一维红外谱的分辨率;2在293~333K范围内,硬脂酸脂肪链处于全反式构象,在348~353K范围内,硬脂酸分子脂肪链构象由全反式构象向无序构象转变;3随着测量温度的升高,硬脂酸分子间的作用力不断降低。
The effect of temperature on the stretching vibration of C-H stearic acid, the conformational change of molecular fat chain and the intermolecular force were studied by Fourier transform infrared spectroscopy. The one-dimensional infrared spectra, second-order derivative infrared spectra, fourth-order derivative infrared spectra and deconvoluted infrared spectra of stearic acid C-H were measured by using variable temperature infrared spectroscopy in the range of 293-393K. The results show that: 1 in the range of 293 ~ 333K, the weak absorption band near 2 965 and 2 870cm-1 in one-dimensional infrared spectrum belongs to asymmetric stretching vibration mode νas (-CH3) and symmetrical stretching vibration mode νs (-CH3), the corresponding derivative spectra and deconvoluted infrared spectra can improve the resolution of one-dimensional infrared spectrum; 2 in the range of 293 ~ 333K, the stearic acid fatty chains are all-trans conformation, in the range of 348 ~ 353K Within the stearic acid molecule, the conformation of the fatty chain changes from the all-trans conformation to the disordered conformation. 3 As the measured temperature increases, the force between the stearic acid molecules decreases.