Formation of β‐distonic oxonium ions: Study of ROCH 2 CH 2 OR′ radical cations

Radical cations derived from the ethers ROCH 2 CH 2 OR′ (R, R′ = H, CH 3 , C 2 5 ) were studied, since β‐distonic oxonium ions are often prepared from ionized ethers of glycol. The first step in the fragmentation is a 1,5‐transfer of an α‐hydrogen to oxygen of a terminal alkoxy group leading to a δ‐distonic oxonium ion. This step is thermo‐neutral and reversible in the ROCH 2 CH 2 OH radical cations and exothermic and irreversible in the dialkyl ether radical cations. Depending on R and R,′ these δ‐distonic oxonium ions fragment by three reactions: the loss of an alcohol or a water molecule, the formation of a β‐distonic oxonium ion ˙CH 2 CH 2 O(H) + R and a 1,4‐H migration between carbon atoms. Competition between these processes is discussed.