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
Z. Yang et al., 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, Journal of the Chemical Society. Faraday transactions, 92(17), 1996, pp. 3173-3182
Citations number
64
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
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.