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标题：Properties, composition, and structure of stearic acid-stearate monolayers on alkaline earth solutions
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作者：David W. Deamer ; Devon W. Meek ; David G. Cornwell 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：1967
卷号：8
期号：3
页码：255-263
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：Interactions between alkaline earth ions and the carboxylate ligand in a stearic acid surface film have been investigated by IR spectrophotometry and surface chemical procedures. The frequency and shape of the carboxylate absorption band and the effect of hydration and pH on band characteristics suggest that beryllium, magnesium, and calcium ions form calcium-type complexes with the stearate ligand while strontium and barium ions form both calcium-type complexes and more ionic barium-type complexes, which have lower carboxylate band maxima. Since IR band frequencies in anhydrous calcium-type complexes are directly proportional to the charge/(crystal radius) ratio, it is apparent that covalency decreases in the order: Be > Mg > Ca > Sr > Ba. The decreasing order of stability constants estimated from spectrophotometric titration data, Be > Ca > Mg > Sr > Ba, demonstrates that calcium behaves anomalously. This anomalous behavior is also apparent in the high solid-to-liquid phase transition temperature and small surface area of the calcium-carboxylate film compared to films composed of complexes with the other ions. A geometric factor related to the ionic radius and the radius of the carboxylate binding site formed by a calcium stearate lattice is proposed to explain the unique properties of calcium-carboxylate surface films. Although the beryllium complex has the highest carboxylate band frequency and stability constant, it gives an atypical ``expanded'' surface film. A hydrogen bonded lattice formed with a soluble beryllium monohydrate is suggested as an explanation for this film property.
关键词：monolayer ; calcium ; magnesium ; alkaline earths ; fatty acid ; metal-carboxylate complex ; IR spectra ; hydration ; stability constant ; transition temperature ; surface area ; copolymeric lattice ; binding site ; ionic radius ; pKa