Decompositions of metastable [C6H12O]+ ions with the oxygen on the third carbon: Ring‐size preferences in [CnH2nO]+˙ ions

The isomerizations preceding the metastable decompositions in the mass spectrometer of a number of [C6H12O]+˙ ions with the oxygen on the third carbon are characterized utilizing deuterium labeling. Hydrogens are transferred in these ions by three‐, five‐ and six‐membered ring rearrangements, with propensities determined by features of the individual reactions. Three‐membered ring hydrogen transfers between α and β‐carbons are preferred to all five‐membered ring hydrogen transfers. However, six‐membered ring hydrogen transfers take place to the apparent exclusion of three‐membered ring hydrogen transfers to enol carbons when the products are of comparable stability. The low‐energy [C6H12O]+˙ isomerizations characterized are predictable from the behavior of their lower homologs. It is concluded that the determinants of these reactions are the same as those of other highly reactive organic intermediates.