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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >The Use of ~(19)F NMR to Interpret the Structural Properties of Perfluorocarboxylate Acids:A Possible Correlation with Their Environmental Disposition
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The Use of ~(19)F NMR to Interpret the Structural Properties of Perfluorocarboxylate Acids:A Possible Correlation with Their Environmental Disposition

机译:〜(19)F NMR的使用来解释全氟羧酸的结构性质:可能与其环境处置的相关性

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The use of perfluorinated anionic carboxylic acids(PFCAs)as surfactants is common and widespread.Investigations of PFCAs have shown that their physical properties and toxicological aspects are dependent upon the carbon chain length.The magnitude of these properties is not a linear function of chain length and as yet no explanation of these unique observations has been made.Their environmental dissemination is expected to be nonproportional to the PFCAs chain length.An understanding of the fundamental underlying reason for this novel physical property,chain length trend,would aid further investigators'interpretation of their environmental and toxicological observations.In this study we have utilized ~(19)F NMR techniques,such as,chemical shift,spin-lattice(T_1),and spin-spin(T_2)relaxation phenomena,coupling constants,and variable-temperature NMR to furnish a qualitative explanation of why increasing the carbon chain length causes unexpected intrinsic property changes within this group of chemicals.Results indicate that polyfluorinated chains adopt helical twist geometry unlike their hydrocarbon counterparts which exhibit a zigzag geometry.Variable-temperature ~(I9)F NMR showed that chain rigidity within these molecules is also a function of the fluorocarbon chain length.There is a distinct change in geometry and rigidity of the acid chain between 8 and 10 carbon lengths.These unique geometric changes in this class of compound must be considered when assessing their dissemination in the environment,for example,in the case of environmental modeling.
机译:全氟阴离子羧酸(PFCA)作为表面活性剂的使用是普遍且广泛的,对PFCA的研究表明其物理性质和毒理学方面取决于碳链长度,这些性质的大小与链长的线性关系不大。预期它们的环境传播与PFCAs链长不成比例。了解这种新颖物理性质的根本原因,链长趋势,将有助于进一步的研究者解释。在这项研究中,我们利用了〜(19)F NMR技术,例如化学位移,自旋晶格(T_1)和自旋自旋(T_2)弛豫现象,耦合常数和变量- NMR进行定性解释,说明为什么增加碳链长度会导致该组中意外的内在特性变化结果表明,多氟链采用螺旋扭曲的几何形状,而不像碳氢化合物对应的那样呈锯齿形。可变温度〜(I9)F NMR表明,这些分子内的链刚性也是碳氟链长度的函数。在8至10个碳长度之间,酸链的几何形状和刚度发生了明显变化。评估此类化合物在环境中的传播时,例如环境建模时,必须考虑此类化合物的这些独特的几何变化。

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