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

The structures of the simplest symmetric primary ethers [(Cn H2n+1 )2 O, n = 1-3] determined under high pressure revealed their conformational preferences and intermolecular interactions. In three new polymorphs of diethyl ether (C2 H5 )2 O, 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 )2 O display analogous transformations of the CH...O bonds. The crystal structure of di-n-propyl ether (C3 H7 )2 O, determined for the first time, is remarkably stable over the whole pressure range investigated from 1.70 up to 5.30 GPa.