SOLUTE-SOLVENT INTERACTIONS IN PERFLUOROCARBON SOLUTIONS OF OXYGEN - AN NMR-STUDY
SOLUTE-SOLVENT INTERACTIONS IN PERFLUOROCARBON SOLUTIONS OF OXYGEN - AN NMR-STUDY
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DOI：
10.1021/ja00403a020
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发表时间：
1981-01-01
影响因子：
15
通讯作者：
DELPUECH, JJ
中科院分区：
文献类型：
--
作者：
HAMZA, MA;SERRATRICE, G;DELPUECH, JJ
含氟化合物，包括烷烃，烯烃，芳烃，胺，和环状和杂环的含氟化合物，研究作为溶剂的氧，使用为此目的的顺磁弛豫诱导的存在下的分子氧到13 C核的相邻溶剂分子在溶液中。弛豫数据由每摩尔分数的溶解氧的弛豫速率Tf]的变化速率qx表示。发现氧的溶解度（以摩尔分数计）与弛豫系数q n之间存在一般相关性，较低的qx值与较高的溶解度相关联。这是由于液体中存在较大的空腔，以便更好的溶剂，因此可以更容易地容纳小的气体分子，而同时氧气和溶剂核之间的磁偶极相互作用减少。发现的溶解度递减的化合物的顺序，脂肪族>环状>芳香族，可以合理化的基础上，从一类溶剂到另一类溶剂的大小递减的空腔。溶解度的顺序似乎主要取决于溶剂分子的形状，而不是分子结构的细节，从而放弃了特定的氟-氧力和可能的电荷转移复合物的替代假设。一些典型的类似烃类的较高弛豫系数可以用同样的概念加以合理化。与烃类相比，氟碳化合物在许多方面具有特殊的物理性质。[1]事实上，人们很快就认识到，除了碳骨架引起的表面相似性之外，碳氢化合物和氟碳化合物分子在物理和化学性质上并不比碳氢化合物和周期表中任何其他元素衍生的化合物之间存在的相似性更相似。由于氢原子核的非常不寻常的性质，氢的化合物实际上形成了一类。氢化和氟化液体的物理性质之间的差异通过氢和碳氟化合物的混合物的非常不理想的行为来强调。这是由于氢氟烃的电离势差异很大，导致分子间色散力存在很大差异。另一个不同之处在于分子结构的细节在计算碳氢化合物的性质中的重要性，而它们在氟化物质中似乎是不重要的参数。因此，液体氟碳化合物更能代表非极性非缔合溶剂。
Fluorinated compounds, including alkanes, alkenes, aromatics, amines, andcyclic and heterocyclic fluorochemicals, are studied as solvents of oxygen, using for this purpose the paramagnetic relaxation induced by the presence of molecular oxygen onto the 13C nuclei of neighboring solvent molecules in the solution. Relaxation data are expressed by the variation rates qx of relaxation rates Tf] per mole fraction of dissolved oxygen. A general correlation is found between the solubility of oxygen (in mole fraction) and the relaxation coefficients q „the lower qx values being associated to the higher solubilities. This was accounted for by the existence of large cavities in the liquid for the bettersolvents, which can thus accommodate small gaseous molecules more easily, while simultaneously the magnetic dipolar interaction between oxygen and solvent nuclei is decreased. The sequence found for compounds of decreasing solubility, aliphatic> cyclic> aromatic, can be rationalized on the basis of cavities of decreasing size from one class of solvents to the other. The order of solubility seems to depend mainly upon the shape of solvent molecules and not upon the details of molecular structure, thus discarding the alternative assumption of specific fluorine-oxygen forces and of a possible charge-transfer complex. The higher relaxation coefficients obtained for some typical analogous hydrocarbons can be rationalized by using the same concepts.Compared to hydrocarbons, fluorocarbons have physical properties which seem to be exceptional in many respects. 1 It was indeed soon recognized that, apartfrom a superficial similarity arising from the carbon skeleton, the hydrocarbon and fluoro-carbon molecules do not offer more analogies in their physical and chemical properties than those existing between hydrocarbons and the compounds deriving from any of the other elements of the periodic table. Compounds of hydrogen form in fact a class by themselves due to the very unusual properties of hydrogen nuclei. The difference between the physical properties of hydrogenated and fluorinated liquids is emphasized by the very nonideal behavior of mixtures of hydro-and fluorocarbons. This was traced to the existence of quite different intermolecular dispersion forces as a result of large differences in the ionization potentials of hydro-anf fluorocarbons. Another difference lies in the importance of the details of molecular structure in ac-counting for the properties of hydrocarbons, while they appear to be unimportant parameters in the fluorinated species. Liquid fluorocarbons are t herefore much more representative of nonpolar nonassociated solvents.