Hydrogen bonding in chloroform solutions of ethylenedioxy ethers. Spectroscopic evidence of bifurcated hydrogen bonds
Hydrogen bonding in chloroform solutions of ethylenedioxy ethers. Spectroscopic evidence of bifurcated hydrogen bonds
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DOI：
10.1021/jp004542e
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发表时间：
2001-05-17
影响因子：
2.9
通讯作者：
Matsuura, H
中科院分区：
文献类型：
--
作者：
Goutev, N;Matsuura, H
采用红外吸收光谱法研究了1,4-二恶烷、1,2-二甲氧基乙烷和二甘醇二甲醚的氯仿溶液。在溶液中加入少量氘化氯仿后，C-D拉伸带的强度被用来探测醚与氯仿之间的氢键强度。假设氯仿分子可分为氢键分子和非氢键分子，采用双组分模型解释了C-D拉伸带强度随氯仿浓度变化的变化。在这个模型的框架中，氢键被认为是醚氧的孤电子对和氯仿分子之间的化学反应。计算了氢键平衡常数，揭示了醚与氯仿氢键配合物的化学计量。结果发现，醚氧的孤电子对在与氯仿形成氢键时不能很好地参与，这很可能是由于位阻的作用。对实验结果的分析还表明，氯仿能与开链醚的相邻氧形成强的分岔氢键。通过从头算分子轨道计算证实了三中心分叉氢键的存在。
Chloroform solutions of 1,4-dioxane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether were studied by means of IR absorption spectroscopy. The intensity of the C-D stretching band of a small amount of deuterated chloroform added to the solutions was used as a probe of the strength of hydrogen bonding between the ethers and chloroform. A two-component model, which assumes that the chloroform molecules can be classified as hydrogen bonded and non-hydrogen bonded, was used to interpret the variations of the intensity of the C-D stretching band on changing the concentration of chloroform. In the frame of this model, the hydrogen bonding was considered as a chemical reaction between the lone electron pairs of the ether oxygens and the chloroform molecules. As a result, the equilibrium constant of hydrogen bonding was estimated and the stoichiometry of the hydrogen bonded complexes of ethers and chloroform was revealed. It was found that the lone electron pairs of the ether oxygens do not participate equally well in hydrogen bonding with chloroform, most probably because of steric hindrance. The analysis of the experimental results also suggested that chloroform can form strong bifurcated hydrogen bonds with the neighboring oxygens of the open-chain ethers. The bifurcated three-centered hydrogen bonds were confirmed by ab initio molecular orbital calculations.