Modeling deoxyribose radicals by neutralization-reionization mass spectrometry. Part 2. Preparation, dissociations, and energetics of 3-hydroxyoxolan-3-yl radical and cation.
The title radical (1) is generated in the gas-phase by collisional neutralization of carbonyl-protonated oxolan-3-one. A 1.5% fraction of 1 does not dissociate and is detected following reionization as survivor ions. The major dissociation of 1 (approximately 56%) occurs as loss of the hydroxyl H atom forming oxolan-3-one (2). The competing ring cleavages by O[bond]C-2 and C-4[bond]C-5 bond dissociations combined account for approximately 42% of dissociation and result in the formation of formaldehyde and 2-hydroxyallyl radical. Additional ring-cleavage dissociations of 1 resulting in the formation of C(2)H(3)O and C(2)H(4)O cannot be explained as occurring competitively on the doublet ground (X) electronic state of 1, but are energetically accessible from the A and higher electronic states accessed by vertical electron transfer. Exothermic protonation of 2 also produces 3-oxo-(1H)-oxolanium cation (3(+)) which upon collisional neutralization gives hypervalent 3-oxo-(1H)-oxolanium radical (3). The latter dissociates spontaneously by ring opening and expulsion of hydroxy radical. Experiment and calculations suggest that carbohydrate radicals incorporating the 3-hydroxyoxolan-3-yl motif will prefer ring-cleavage dissociations at low internal energies or upon photoexcitation by absorbing light at approximately 590 and approximately 400 nm.
Vivekananda
Shetty
S
Department of Chemistry, University of Washington, Seattle, 98195, USA.
Sadílek
Martin
M
Chen
Xiaohong
X
Adams
Luke E
LE
Turecek
Frantisek
F
D002412:Cations; D003198:Computer Simulation; D003855:Deoxyribose / Q000032:analysis* / Q000737:chemistry*; D004735:Energy Transfer; D005609:Free Radicals; D005740:Gases / Q000737:chemistry; D007536:Isomerism; D013058:Mass Spectrometry / Q000379:methods*; D008956:Models, Chemical
D002412:Cations; D005609:Free Radicals; D005740:Gases; D003855:Deoxyribose