NUCLEAR-MAGNETIC-RESONANCE STUDY OF SELF-ASSOCIATION OF SMALL HYDROPHOBIC SOLUTES IN WATER - SALT EFFECTS AND THE LYOTROPIC SERIES
NUCLEAR-MAGNETIC-RESONANCE STUDY OF SELF-ASSOCIATION OF SMALL HYDROPHOBIC SOLUTES IN WATER - SALT EFFECTS AND THE LYOTROPIC SERIES
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DOI：
10.1039/ft9938901215
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发表时间：
1993-04-21
期刊：
影响因子：
--
通讯作者：
MELELEO, A
中科院分区：
文献类型：
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作者：
HOLZ, M;GRUNDER, R;MELELEO, A
应用核磁共振技术研究了二甲亚砜(DMSO)-水、叔丁醇(Bu(t)OH)-水和四甲基脲(TMU)-水混合物中相对较小的疏水性有机组分的自缔合行为。所谓的缔合参数 A22 基本上是从 H-1 核的实验分子间偶极-偶极弛豫数据和有机组分自扩散系数的 NMR 测量中获得的，已被确定。 A22 在所有所研究的系统中的组成依赖性表明，有机组分发生了自缔合。关联参数 A(ij) 和 Kirkwood-Buff 积分 G(ij) 是相关量，可能会产生互补信息。因此，对于 DMSO 和 Bu(t)OH 的水性混合物，给出了 A22 和 G22 之间的定性比较。目前工作的主要目的是研究盐对缔合行为的影响。含盐混合物获得的 A22 参数表明，盐（DMSO-水中的 LiI、CsI 和 CsAc；Bu(t)OH-水中的 LiBr 和 CsBr；TMU-水中的 LiBr、LiClO4 和 LiAc）改变了有机物质之间的吸引相互作用。对于 Bu(t)OH 和 TMU，盐的影响基本上遵循溶致级数或霍夫迈斯特级数；然而，对于 DMSO，离子的有效性却相反。我们的结果表明 Bu(t)OH 和 TMU 存在疏水缔合，而对于 DMSO 显然存在另一种短程相互作用。最后，做出了新的尝试来解释霍夫迈斯特级数中众所周知的阳离子和阴离子的结构破坏能力的逆序。
The self-association behaviour of the relatively small hydrophobic organic components in mixtures of dimethyl sulfoxide (DMSO)-water, of tert-butyl alcohol (Bu(t)OH)-water and of tetramethylurea(TMU)-water has been studied by the application of an NMR technique. The so-called association parameter A22, which essentially is obtained from experimental intermolecular dipole-dipole relaxation data of H-1 nuclei and from NMR measurements of the self-diffusion coefficients of the organic components, has been determined. The composition dependence of A22 in all the systems under investigation shows that self-association of the organic component occurs. The association parameters A(ij) and the Kirkwood-Buff integrals G(ij) are related quantities, which might yield complementary information. Thus a qualitative comparison between A22 and G22 is given for aqueous mixtures of DMSO and of Bu(t)OH. The main aim of the present work is the study of the influence of salts on the association behaviour. The A22 parameters obtained for salt-containing mixtures show that the salts (LiI, CsI and CsAc in DMSO-water; LiBr and CsBr in Bu(t)OH-water; LiBr, LiClO4 and LiAc in TMU-water) change the attractive interaction between the organic species. For Bu(t)OH and TMU the influence of salt essentially follows the lyotropic or Hofmeister series; however, for DMSO the reverse sequence of effectiveness of the ions is found. Our results indicate hydrophobic association for Bu(t)OH and TMU, while for DMSO obviously a short-range interaction of another kind is acting. Finally, a new attempt is made to explain the well known reverse order in the Hofmeister series for cations and for anions with respect to their structure-breaking ability.