Journal of the Chemical Society - Faraday Transactions p. 3173 - 3182 (1996)
Update date:2022-08-02
Topics:
Yang, Zhuo
Yu, Ga-Er
Cooke, Jennifer
Ali-Adib, Ziad
Viras, Kyriakos
Matsuura, Hiroatsu
Ryan, Anthony J.
Booth, Colin
Cyclic heptacosa(oxyethyelene) (cyclo-E27, 81-crown-27) was prepared from linear α-hydro, ω-hydroxy-heptacosa(oxyethylene) by reaction with tosyl chloride under alkaline conditions, purified by preparative-scale gel permeation chromatography, and studied by laser-Raman spectroscopy, wide-angle and small-angle X-ray scattering, and differential scanning calorimetry. Comparison was made with the properties of linear oligo(oxyethylene) dimethyl ethers (including C1E27C1). The sub-cell of the crystalline cyclic oligomer was the same as that of its linear counterparts, i.e. the same as that of high-molar-mass poly(oxyethylene). However, the cyclic oligomer crystallised as a twice-folded ring, as confirmed by its long spacing and the frequency of its single-node longitudinal acoustic mode (LAM-1). Enthalpies of fusion and melting temperatures were analysed to provide estimates of the enthalpy and entropy of formation of a fold in an oligo(oxyethylene) layer crystal.
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