The Reactions of Metastable +. Ions with the Oxygen on the Second Carbon

Article abstract of DOI:10.1002/oms.1210190802

Nearly all +.> isomers with the oxygen on the second carbon are shown to interconvert with each other and lose methyl and ethylene at the threshold for dissociation.The methyls contain the carbon from the 1- and 5-positions with about equal frequency, and C(3) or perhaps C(4) about half as often as either terminal carbon.CH3CH2CH2CO⁺ is formed by loss of the C(1) methyl and CH2=CHC(O⁺H)CH3 by loss of the C(5) methyl.Hydrogen transfer between C(5) and the oxygen and between the oxygen and C(4) are facile, and 1,2-hydrogen transfers between C(3) and C(4) occur with high frequency.Extensive skeletal rearrangements also take place by 1,2-shifts between C(2), C(3) and C(4).We attribute the occurence of the three-center shifts between C(2), C(3) and C(4) to the presence of considerable charge density on C(2) and C(3) in many of the ^+. isomers.The isomerizations of ^+. can be considered a mixture of free radical and carbocation reactions.Strong similarities exist between the isomerizations of metastable ^+. ions with the oxygen on the second carbon and those of isomers of ionized butanoic acid, methyl butanoate and n-butanal.