POLAR, APROTIC-SOLVENTS AND THE HYDROPHOBIC EFFECT
POLAR, APROTIC-SOLVENTS AND THE HYDROPHOBIC EFFECT
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DOI：
10.1021/j150658a043
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发表时间：
1984-01-01
影响因子：
--
通讯作者：
GRECO, FA
中科院分区：
文献类型：
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作者：
GRECO, FA
目前的疏水效应理论将水和烷烃混合时熵的减少归因于氢键的增加。本文表明，水-癸烷界面的形成熵（-0.162 erg/（deg cm 1 2））与癸烷和！的形成熵具有相似的大小。N，N-二甲基乙酰胺（-0.152 erg/（deg cm 2））、二甲亚砜（-0.125 erg/（deg cm 2））和乙腈（-0.159 erg/（deg cm 2））。由于这些极性的非质子溶剂不能在它们之间形成氢键，所以一定存在一种机制，通过这种机制熵可以减少而不调用氢键所特有的性质。本文提出了一个熵变与自由体积的定性模型，水和烷烃的不相容性理论为讨论影响胶束、蛋白质和生物膜的因素提供了一个有用的框架。1 - 3所有这些理论都集中在与水和烷烃的相互作用相关的熵的减少上，因为这种减少解释了混合的不可解释的自由能。当水和烷烃在两种不同的环境中相互作用时，熵损失的大小相似：作为两个由界面分离的体相和作为烷烃在水中的溶质和溶剂。理想情况下，一个完整的理论应该解释这两种情况，但许多作者都集中在烷烃在水中的溶解度，以甲烷在水中作为paradigm。2· 6”8 Némethy，Scheraga，and Kauzmann 9已经清楚地表明了一个广泛持有的信念，即”.这个熵项是由于水状态的变化而产生的，并且必须归因于水分子的有序性增加，即氢键的增加。然而，米勒和希尔德布兰德强调了氢键对水的热容的贡献。他们将熵的减少归因于“当惰性分子被引入时......
A current theoryof the hydrophobic effect assigns the decrease in entropy upon mixing water and alkane to an increase in hydrogen bonding. This paper shows that the entropy of formation of a water-decane interface (-0.162 erg/(deg cm1 2)) has a magnitude similar to those of decane and! V, lV-dimethylacetamide (-0.152 erg/(deg cm2)), dimethyl sulfoxide (-0.125 erg/(deg cm2)), and acetonitrile (-0.159 erg/(deg cm2)). Since these polar, aprotic solvents cannot form hydrogen bonds among themselves, a mechanism must exist by which entropy can decrease without invoking properties unique to hydrogen bonds. A qualitative model relating entropy changes to free volume is proposed.Theories concerning the immiscibility of water and alkane have created a useful framework in which to discuss factors affecting micelles, proteins, and biological membranes. 1" 3 All of these theories focus on the decrease in entropy associated with the interaction of water and alkane, because this decrease accounts, for the unfavorablefree energy of mixing. Entropy losses of similar magnitude occur when water and alkane interact in twodifferent settings: as two bulk phases separatedby an interface and as solute and solvent for alkane in water. 4 5" 6 7Ideally, a complete theory should explain both cases but many authors have focused on the solubility of alkane in water, taking methane in water as para-digm. 2· 6" 8 Némethy, Scheraga, and Kauzmann9 have clearly stated a widely held belief that"... this entropy term arises owing to changes in the state of water and has to be attributed to in-creased ordering of water molecules, ie, to an increase in hydrogen bonding.” However, Miller and Hildebrand10 have emphasized the contribution of hydrogen bonds to the heat capacity of water. They assign theentropy decrease to thenotion that “when inert molecules are introduced...