التفاصيل البيبلوغرافية
| العنوان: |
Infrared signature of the hydroperoxyalkyl intermediate (·QOOH) in cyclohexane oxidation: An isomer-resolved spectroscopic study. |
| المؤلفون: |
Roy, Tarun Kumar, Qian, Yujie, Sojdak, Christopher A., Kozlowski, Marisa C., Klippenstein, Stephen J., Lester, Marsha I. |
| المصدر: |
Journal of Chemical Physics; 7/21/2024, Vol. 161 Issue 3, p1-9, 9p |
| مصطلحات موضوعية: |
LASER-induced fluorescence, CYCLOHEXANE, RADICALS (Chemistry), PERTURBATION theory, OXIDATION, ISOMERS, COLLISION induced dissociation |
| مستخلص: |
Infrared (IR) action spectroscopy is utilized to characterize carbon-centered hydroperoxy-cyclohexyl radicals (·QOOH) transiently formed in cyclohexane oxidation. The oxidation pathway leads to three nearly degenerate ·QOOH isomers, β-, γ-, and δ-QOOH, which are generated in the laboratory by H-atom abstraction from the corresponding ring sites of the cyclohexyl hydroperoxide (CHHP) precursor. The IR spectral features of jet-cooled and stabilized ·QOOH radicals are observed from 3590 to 7010 cm−1 (∼10–20 kcal mol−1) at energies in the vicinity of the transition state (TS) barrier leading to OH radicals that are detected by ultraviolet laser-induced fluorescence. The experimental approach affords selective detection of β-QOOH, arising from its significantly lower TS barrier to OH products compared to γ and δ isomers, which results in rapid unimolecular decay and near unity branching to OH products. The observed IR spectrum of β-QOOH includes fundamental and overtone OH stretch transitions, overtone CH stretch transitions, and combination bands involving OH or CH stretch with lower frequency modes. The assignment of β-QOOH spectral features is guided by anharmonic frequencies and intensities computed using second-order vibrational perturbation theory. The overtone OH stretch (2νOH) of β-QOOH is shifted only a few wavenumbers from that observed for the CHHP precursor, yet they are readily distinguished by their prompt vs slow dissociation rates to OH products. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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