Modeling deoxyribose radicals by neutralization-reionization mass spectrometry. Part 1. Preparation, dissociations, and energetics of 2-hydroxyoxolan-2-yl radical, neutral isomers, and cations

AbstractCollisional neutralization of several isomeric C4H7O2 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 (2H and 18O), 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 (∼90%) pathway is initiated by cleavage of the ring C-5O bond in 1 and proceeds to form ethylene and ·CH2COOH 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, ∼9%) and cleavage of the C-3C-4 bonds (