Conformation–aggregation interplay in the simplest aliphatic ethers probed under high pressure

Abstract

The most stable trans–trans conformation of the di­ethyl ether molecule hinders its aggregation due to restricted access to the oxygen atom. This hindrance can be removed by conformational transformation under high pressure.

The structures of the simplest symmetric primary ethers [(CnH₂n₊₁)₂O, n = 1–3] determined under high pressure revealed their conformational preferences and intermolecular interactions. In three new polymorphs of di­ethyl ether (C₂H₅)₂O, high pressure promotes intermolecular CH⋯O contacts and enforces a conversion from the trans–trans conformer present in the α, β and γ phases to the trans–gauche conformer, which is higher in energy by 6.4 kJ mol⁻¹, in the δ phase. Two new polymorphs of di­methyl ether (CH₃)₂O display analogous transformations of the CH⋯O bonds. The crystal structure of di-n-propyl ether (C₃H₇)₂O, determined for the first time, is remarkably stable over the whole pressure range investigated from 1.70 up to 5.30 GPa.