Metastable Decompositions of C5H10O+. Ions with the Oxygen on the Middle Carbon: A Test for Energy Randomization

Article abstract of DOI:10.1021/ja00536a006

This study was undertaken to define the mechanisms of metastable decomposition of C5H10O^+. ions with the oxygen on the middle carbon, and to test the assumption that internal energy becomes randomly distributed prior to the unimolecular decompositions of gaseous ions.CH3CH2C(=OH⁺)CH2CH2^. (2), CH3CH2C(=OH⁺)^.CHCH3 (3), and CH3CH2C(OH^+.)HCH=CH2 (4) all rearrange to CH3CH2C(=O^+.)CH2CH3 (1) prior to metastable decomposition.However, 2 - 4 lose ethyl 50 - 100 times as often as they lose ethane following rearrangement to 1, while 1 formed by ionization of 3-pentanone loses exclusively ethane.These differences are attributed to excess energy in the isomerized ions. 3-Pentanone ions formed by isomerization of 2 - 4 lose ethyl and ethane from opposite sides at unequal rates, possibly owing to incomplete randomization of energy following isomerization.