物理化学学报 >> 2013, Vol. 29 >> Issue (10): 2114-2122.doi: 10.3866/PKU.WHXB201305103

热分析动力学和热动力学 上一篇    下一篇

大环疏水效应: 冠醚在DMF+H2O混合物中的焓对作用

程维娜1, 胡新根1, 邵爽2   

  1. 1 温州大学化学与材料工程学院, 浙江 温州 325035;
    2 浙江外国语学院化学系, 杭州 310012
  • 收稿日期:2013-03-26 修回日期:2013-05-09 发布日期:2013-09-26
  • 通讯作者: 胡新根 E-mail:hxgwzu@126.com
  • 基金资助:

    国家自然科学基金(21073132)资助项目

Macrocyclic Hydrophobic Effect:Enthalpic Pairwise Interactions of Crown Ethers in Mixtures of DMF and Water

CHENG Wei-Na1, HU Xin-Gen1, SHAO Shuang2   

  1. 1 College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, Zhejiang Province, P. R. China;
    2 Department of Chemistry, Zhejiang International Studies University, Hangzhou 310012, P. R. China
  • Received:2013-03-26 Revised:2013-05-09 Published:2013-09-26
  • Contact: HU Xin-Gen E-mail:hxgwzu@126.com
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21073132).

摘要:

利用等温滴定微量热法测定了298.15 K时12-冠-4、15-冠-5、18-冠-6和4,13-二氮杂-18-冠-6四种冠醚在纯水及不同质量分数(w=0-0.3)的N,N-二甲基甲酰胺(DMF)+H2O混合物中的稀释焓, 根据McMillan-Mayer理论计算得到相应的焓对作用系数(hxx). 实验发现, hxx均为较大的正值, 表明在冠醚-冠醚自相互作用中疏水性成分占绝对优势, 主要表现为两种机制: (1) 当疏水-疏水作用发生时, 共球交盖使得水结构形成减少, 对hxx有正的贡献; (2) 当疏水-亲水作用发生时, 共球交盖使得水结构破坏增加, 对hxx有正的贡献. 此外, 四种冠醚hxx的大小关系为: hxx(18-冠-6)>hxx(4,13-二氮杂-18-冠-6)≈hxx(15-冠-5)>hxx(12-冠-4), 表明冠醚环越大, 疏水-疏水作用越强, 存在显著的大环疏水效应.

关键词: 冠醚, 二甲基甲酰胺+水混合物, 稀释焓, 焓对作用, 疏水-亲水平衡, 大环疏水效应, 等温滴定微量热法

Abstract:

The dilution enthalpies of four crown ethers, namely 12-crown-4, 15-crown-5, 18-crown-6, and 4,13-diaza-18-crown-6, in pure water and mixtures of N,N-dimethylformamide (DMF) and water of various mass fraction (w=0-0.3) were determined at 298.15 K by isothermal titration microcalorimetry. The corresponding enthalpic pairwise interaction coefficients (hxx) were evaluated according to the McMillan-Mayer theory. Values of hxx were all positive and large, which indicates that hydrophobic components predominate in crown-crown self-interactions. There are two main kinds of mechanisms: (1) When hydrophobic-hydrophobic interactions occur, cosphere overlapping reduces the formation of water structure, which makes a positive contribution to hxx. (2) Hydrophobic-hydrophilic interactions increasingly destroy the water structure because of cosphere overlapping, which also makes a positive contribution to hxx. In addition, hxx values of the four crown ethers follow the order: hxx(18-crown-6)>hxx(4,13-diaza-18-crown-6)≈ hxx(15-crown-5) >hxx(12-crown-4), which indicates that the larger the size of the crown ether ring, the stronger the hydrophobic-hydrophobic interaction; namely, that crown ethers are subject to macrocyclic hydrophobic effects.

Key words: Crown ether, N,N-dimethylformamide+H2Omixture, Dilution enthalpy, Enthalpic pairwise interaction, Hydrophobic-hydrophilic equilibrium, Macrocyclic hydrophobic effect, Isothermal titration calorimetry

MSC2000: 

  • O645