| Title: | Infrared spectroscopic signature of a hydroperoxyalkyl radical (*QOOH) |
| Author(s): | Hansen AS; Bhagde T; Qian Y; Cavazos A; Huchmala RM; Boyer MA; Gavin-Hanner CF; Klippenstein SJ; McCoy AB; Lester MI; |
| Address: | "Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA. Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA. Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA" |
| ISSN/ISBN: | 1089-7690 (Electronic) 0021-9606 (Linking) |
| Abstract: | "Infrared (IR) action spectroscopy is utilized to characterize a prototypical carbon-centered hydroperoxyalkyl radical (*QOOH) transiently formed in the oxidation of volatile organic compounds. The *QOOH radical formed in isobutane oxidation, 2-hydroperoxy-2-methylprop-1-yl, *CH(2)(CH(3))(2)COOH, is generated in the laboratory by H-atom abstraction from tert-butyl hydroperoxide (TBHP). IR spectral features of jet-cooled and stabilized *QOOH radicals are observed from 2950 to 7050 cm(-1) at energies that lie below and above the transition state barrier leading to OH radical and cyclic ether products. The observed *QOOH features include overtone OH and CH stretch transitions, combination bands involving OH or CH stretch and a lower frequency mode, and fundamental OH and CH stretch transitions. Most features arise from a single vibrational transition with band contours well simulated at a rotational temperature of 10 K. In each case, the OH products resulting from unimolecular decay of vibrationally activated *QOOH are detected by UV laser-induced fluorescence. Assignments of observed *QOOH IR transitions are guided by anharmonic frequencies computed using second order vibrational perturbation theory, a 2 + 1 model that focuses on the coupling of the OH stretch with two low-frequency torsions, as well as recently predicted statistical *QOOH unimolecular decay rates that include heavy-atom tunneling. Most of the observed vibrational transitions of *QOOH are readily distinguished from those of the TBHP precursor. The distinctive IR transitions of *QOOH, including the strong fundamental OH stretch, provide a general means for detection of *QOOH under controlled laboratory and real-world conditions" |
| Notes: | "PubMed-not-MEDLINEHansen, Anne S Bhagde, Trisha Qian, Yujie Cavazos, Alyssa Huchmala, Rachel M Boyer, Mark A Gavin-Hanner, Coire F Klippenstein, Stephen J McCoy, Anne B Lester, Marsha I eng 2022/01/10 J Chem Phys. 2022 Jan 7; 156(1):014301. doi: 10.1063/5.0076505" |
