Dynamical Molecular Conformation and Structure of Cluster for Saturated and Unsaturated Fatty Acids in the Liquid State

本文通过密度、自扩散系数、~ 1C NMR自旋-晶格弛豫时间和X射线衍射研究了三种顺式不饱和脂肪酸（顺-6-、顺-9-、顺-11-十八碳烯酸）、反式不饱和脂肪酸（反-9-十八碳烯酸）和正饱和脂肪酸（十八烷酸）在液态下的平移运动、动态分子构象和聚集态结构<13>。在350 K以下，自扩散系数D的大小顺序为顺式不饱和酸&gt;反式酸&gt;饱和酸，在350 K以上，反式酸的D值上升到顺式酸的D值。另一方面，酸的密度ρ也按顺式酸&gt;反式酸&gt;饱和酸的顺序下降;密度的顺序与从自扩散系数和其他物理性质如熔点和熔化热的结果所预期的相反。酸的D值和ρ值之间的这种差异可以用它们液体中的团簇模型很好地解释。

The translational movement, the dynamical molecular conformation, and the aggregate structure in the liquid state for three kinds of cis-type unsaturated fatty acids (cis-6-, cis-9-, and cis-11-octadecenoic acids), trans-type unsaturated acid (trans-9-octadecenoic acid), and n-saturated acid (octadecanoic acid) have been studied through the measurements of density, self-diffusion coefficient, ^<13>C NMR spin-lattice relaxation time, and X-ray diffraction. The magnitude of the self-diffusion coefficient, D, fell in sequence of cis-type unsaturated acids > trans-type acids > saturated acid below 350 K.Above 350 K the value of D for the trans-type acid rose to those for the cis-type acids. On the other hand, the density ρ for the acids also fell in the order of cis-type acids > trans-type acid > saturated acid ; the order of the density is just opposite to that expected from the results of the self-diffusion coefficient and other physical properties such as melting point and heat of fusion. This discrepancy between D and ρ values for the acids is well explained by the models of the clusters in their liquids.