K. Ślepokura, T. Kozlecki, T. Lis
Feb 28, 2003
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0
Influential Citations
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Journal
Journal of Molecular Structure
Abstract
Abstract The crystal and molecular structures of the cis- and trans -isomers of 2,5-diethoxy-2,5-bis(hydroxymethyl)-[1,4]-dioxane have been determined by X-ray analysis. The cis - ( I ) and trans -isomers ( II ) crystallize in the monoclinic (space group P 2 1 / c ) and orthorhombic ( Pbca ) system, respectively. The [1,4]-dioxane ring of the cis -isomer molecule adopts a twist-boat conformation, while the ring of the trans -isomer is a chair. The two ethoxy groups in II are in more crowded axial positions, due to the anomeric effect. The anomeric effect, stronger in the cis -isomer, influences its stability, despite the presence of two bulky hydroxymethyl groups in the equatorial orientation and the low-energy chair conformation of the trans -isomer. Both hydroxyl groups in I and II act as donors in intermolecular two-centre and three-centre O–H⋯O hydrogen bonding, which may be classified as medium strong and weak. Additionally, there are C–H⋯O hydrogen interactions in each crystal; that in the cis -isomer is intramolecular.