As models for the ionization of orthoesters, a series of 1,3-dioxan-2-ylium salts have been prepared and characterized. The properties of 1,3-dioxan-2-ylium hexachloroantimonate1, 5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate2, 2-methyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate3, and 2-phenyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate4, have been studied by1H and13C NMR spectroscopy. The structures of3and4have been determined using X-ray crystallography. Salts3and4both crystallize in monoclinic crystal systems. For3, the space group isC2/c, witha = 30.192(4) Å,b = 9.613(2) Å,c = 12.742(2) Å, β = 109.71(1)°,V = 3482(1) Å3, and Z = 8. Complex4crystallizes in the space groupP21/n, witha = 10.638(2) Å,b = 11.849(2) Å,c = 16.970(3) Å, β = 106.84(1)°,V = 2047(1) Å3, and Z = 4. The geometries of3and4are similar with the ether oxygen disposed over the dioxan-2-ylium ring. However, the interaction between the ether oxygen and the cationic centre is not significant due to the large internuclear distance observed. The cation5, in which the carbon chain length between the ether oxygen and C(5) was increased, was prepared. This ion was found to undergo a reversible, intramolecular rearrangement resulting in the formation of 1-methyl-4-acetoxymethyl-tetrahydrofuranyl oxonium hexachloroantimonate11.