title: Modeling deoxyribose radicals by neutralization-reionization mass spectrometry. Part 1. Preparation, dissociations, and energetics of 2-hydroxyoxolan-2-yl radical, neutral isomers, and cations.
abstract: Collisional neutralization of several isomeric C(4)H(7)O(2) cations is used to generate radicals that share some structural features with transient species that are thought to be produced by radiolysis of 2-deoxyribose. The title 2-hydroxyoxolan-2-yl radical (1) undergoes nearly complete dissociation when produced by femtosecond electron transfer from thermal organic electron donors dimethyl disulfide and N,N-dimethylaniline in the gas phase. Product analysis, isotope labeling ((2)H and (18)O), and potential energy surface mapping by ab initio calculations at the G2(MP2) and B3-PMP2 levels of theory and in combination with Rice-Ramsperger-Kassel-Marcus (RRKM) kinetic calculations are used to assign the major and some minor pathways for 1 dissociations. The major (approximately 90%) pathway is initiated by cleavage of the ring C-5[bond]O bond in 1 and proceeds to form ethylene and *CH(2)COOH as main products, whereas loss of a hydrogen atom forms 4-hexenoic acid as a minor product. Loss of the OH hydrogen atom forming butyrolactone (2, approximately 9%) and cleavage of the C-3[bond]C-4 bonds (<1%) in 1 are other minor pathways. The major source of excitation in 1 is by Franck-Condon effects that cause substantial differences between the adiabatic and vertical ionization of 1 (5.40 and 6.89 eV, respectively) and vertical recombination in the precursor ion 1(+) (4.46 eV). (+)NR(+) mass spectra distinguish radical 1 from isomeric radicals 2-oxo-(1H)oxolanium (3), 1,3-dioxan-2-yl (9), and 1,3-dioxan-4-yl (10) that were generated separately from their corresponding ion precursors.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, 98195, USA.
authors.forename: Shetty
authors.initials: S
authors.lastname: Vivekananda
authors.forename: Martin
authors.initials: M
authors.lastname: Sadílek
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Chen
authors.forename: Frantisek
authors.initials: F
authors.lastname: Turecek
mesh_terms: 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
chemical_list: D002412:Cations; D005609:Free Radicals; D005740:Gases; D003855:Deoxyribose