PREPARATION AND CRYSTALLINITY OF A LARGE UNSUBSTITUTED CROWN-ETHER, CYCLIC HEPTACOSA(OXYETHYLENE) (CYCLO-E(27), 81-CROWN-27), STUDIED BY RAMAN-SPECTROSCOPY, X-RAY-SCATTERING AND DIFFERENTIAL SCANNING CALORIMETRY

Cyclic heptacosa(oxyethyelene) (cyclo-E(27), 81-crown-27) was prepared from linear alpha-hydro, omega-hydroxy-heptacosa(oxyethylene) by reac tion with tosyl chloride under alkaline conditions, purified by prepar ative-scale gel permeation chromatography, and studied by laser-Raman spectroscopy, wide-angle and small-angle X-ray scattering, and differe ntial scanning calorimetry. Comparison was made with the properties of linear oligo(oxyethylene) dimethyl ethers (including C(1)E(27)C(1)). The sub-cell of the crystalline cyclic oligomer was the same as that o f its linear counterparts, i.e. the same as that of high-molar-mass po ly(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 ent halpy and entropy of formation of a fold in an oligo(oxyethylene) laye r crystal.