Solvation structures of cyclic compounds: the crown ethers

Crown ethers are cyclic molecules formed by joining ether groups into a ring. These compounds have many interesting solution properties, including their ability to bind strongly to certain cations. We request 4 days of beamtime on NIMROD to study the structure of concentrated and dilute solutions of 15-crown-5 (15 atoms in the ring, and 5 ether groups) in two different solvents: Methanol and Dimethyl Ether (DME). This proposal will enable us to determine the microscopic solvation of crown ethers in the presence and absence of hydrogen bonding, both with and without complexed ions. These experiments will exploit the unique ability of neutron scattering to elucidate of liquid structure, and will use isotopic labelling of the solvent molecules to highlight very subtle structural features. This approach will enable us to answer many fundamental questions regarding crown ether solvation.

冠醚（Crown ethers）是通过醚基连接成环形成的环状分子。这类化合物具有多种有趣的溶液性质，包括与特定阳离子强烈结合的能力。我们申请在NIMROD上使用4天的束流时间，以研究15-冠-5（环内含15个原子及5个醚基）在两种不同溶剂（甲醇与二甲醚，DME）中的浓溶液和稀溶液结构。本提案将使我们能够确定冠醚在有无氢键存在、有无络合离子存在条件下的微观溶剂化行为。这些实验将利用中子散射（neutron scattering）阐明液体结构的独特能力，并通过溶剂分子的同位素标记（isotopic labelling）突出非常细微的结构特征。这种方法将使我们能够回答有关冠醚溶剂化的许多基本问题。