Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation
The C[subscript 9]H[subscript 11] potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C[subscript 9]H[subscript 11] PES has already been extensively studied both experimentally (under...
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Royal Society of Chemistry (RSC)
2019
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| Online Access: | http://hdl.handle.net/1721.1/120936 https://orcid.org/0000-0002-6797-8578 https://orcid.org/0000-0002-8475-7697 https://orcid.org/0000-0003-2108-3004 https://orcid.org/0000-0003-2603-9694 |
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| author | Buras, Zachary Chu, Te-Chun Jamal, Adeel Yee, Nathan Wa-Wai Middaugh, Joshua Eugene Green Jr, William H |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Buras, Zachary Chu, Te-Chun Jamal, Adeel Yee, Nathan Wa-Wai Middaugh, Joshua Eugene Green Jr, William H |
| author_sort | Buras, Zachary |
| collection | MIT |
| description | The C[subscript 9]H[subscript 11] potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C[subscript 9]H[subscript 11] PES has already been extensively studied both experimentally (under single-collision and thermal conditions) and theoretically, new insights were made in this work by taking a new experimental approach: flash photolysis combined with time-resolved molecular beam mass spectrometry (MBMS) and visible laser absorbance. The C[subscript 9]H[subscript 11] PES was experimentally accessed by photolytic generation of the phenyl radical and subsequent reaction with excess propene (C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6]). The overall kinetics of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] was measured using laser absorbance with high time-resolution from 300 to 700 K and was found to be in agreement with earlier measurements over a lower temperature range. Five major product channels of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] were observed with MBMS at 600 and 700 K, four of which were expected: hydrogen (H)-abstraction (measured by the stable benzene, C[subscript 6]H[subscript 6], product), methyl radical (CH[subscript 3])-loss (styrene detected), H-loss (phenylpropene isomers detected) and radical adduct stabilization. The fifth, unexpected product observed was the benzyl radical, which was rationalized by the inclusion of a previously unreported pathway on the C[subscript 9]H[subscript 11] PES: aromatic-catalysed 1,2-H-migration and subsequent resonance stabilized radical (RSR, benzyl radical in this case) formation. The current theoretical understanding of the C[subscript 9]H[subscript 11] PES was supported (including the aromatic-catalyzed pathway) by quantitative comparisons between modelled and experimental MBMS results. At 700 K, the branching to styrene + CH[subscript 3] was 2-4 times greater than that of any other product channel, while benzyl radical + C[subscript 2]H[subscript 4] from the aromatic-catalyzed pathway accounted for ∼10% of the branching. Single-collision conditions were also simulated on the updated PES to explain why previous crossed molecular beam experiments did not see evidence of the aromatic-catalyzed pathway. This experimentally validated knowledge of the C[subscript 9]H[subscript 11] PES was added to the database of the open-source Reaction Mechanism Generator (RMG), which was then used to generalize the findings on the C[subscript 9]H[subscript 11] PES to a slightly more complicated alkylaromatic system. |
| first_indexed | 2024-09-23T11:24:28Z |
| format | Article |
| id | mit-1721.1/120936 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T11:24:28Z |
| publishDate | 2019 |
| publisher | Royal Society of Chemistry (RSC) |
| record_format | dspace |
| spelling | mit-1721.1/1209362022-10-01T03:26:19Z Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation Buras, Zachary Chu, Te-Chun Jamal, Adeel Yee, Nathan Wa-Wai Middaugh, Joshua Eugene Green Jr, William H Massachusetts Institute of Technology. Department of Chemical Engineering Buras, Zachary Chu, Te-Chun Jamal, Adeel Yee, Nathan Wa-Wai Middaugh, Joshua Eugene Green Jr, William H The C[subscript 9]H[subscript 11] potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C[subscript 9]H[subscript 11] PES has already been extensively studied both experimentally (under single-collision and thermal conditions) and theoretically, new insights were made in this work by taking a new experimental approach: flash photolysis combined with time-resolved molecular beam mass spectrometry (MBMS) and visible laser absorbance. The C[subscript 9]H[subscript 11] PES was experimentally accessed by photolytic generation of the phenyl radical and subsequent reaction with excess propene (C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6]). The overall kinetics of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] was measured using laser absorbance with high time-resolution from 300 to 700 K and was found to be in agreement with earlier measurements over a lower temperature range. Five major product channels of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] were observed with MBMS at 600 and 700 K, four of which were expected: hydrogen (H)-abstraction (measured by the stable benzene, C[subscript 6]H[subscript 6], product), methyl radical (CH[subscript 3])-loss (styrene detected), H-loss (phenylpropene isomers detected) and radical adduct stabilization. The fifth, unexpected product observed was the benzyl radical, which was rationalized by the inclusion of a previously unreported pathway on the C[subscript 9]H[subscript 11] PES: aromatic-catalysed 1,2-H-migration and subsequent resonance stabilized radical (RSR, benzyl radical in this case) formation. The current theoretical understanding of the C[subscript 9]H[subscript 11] PES was supported (including the aromatic-catalyzed pathway) by quantitative comparisons between modelled and experimental MBMS results. At 700 K, the branching to styrene + CH[subscript 3] was 2-4 times greater than that of any other product channel, while benzyl radical + C[subscript 2]H[subscript 4] from the aromatic-catalyzed pathway accounted for ∼10% of the branching. Single-collision conditions were also simulated on the updated PES to explain why previous crossed molecular beam experiments did not see evidence of the aromatic-catalyzed pathway. This experimentally validated knowledge of the C[subscript 9]H[subscript 11] PES was added to the database of the open-source Reaction Mechanism Generator (RMG), which was then used to generalize the findings on the C[subscript 9]H[subscript 11] PES to a slightly more complicated alkylaromatic system. Think Global Education Trust 2019-03-12T19:37:30Z 2019-03-12T19:37:30Z 2018-04 2018-02 2019-03-05T14:07:09Z Article http://purl.org/eprint/type/JournalArticle 1463-9076 1463-9084 http://hdl.handle.net/1721.1/120936 Buras, Zachary J., Te-Chun Chu, Adeel Jamal, Nathan W. Yee, Joshua E. Middaugh, and William H. Green. “Phenyl Radical + Propene: a Prototypical Reaction Surface for Aromatic-Catalyzed 1,2-Hydrogen-Migration and Subsequent Resonance-Stabilized Radical Formation.” Physical Chemistry Chemical Physics 20, no. 19 (2018): 13191–13214. © 2018 the Owner Societies https://orcid.org/0000-0002-6797-8578 https://orcid.org/0000-0002-8475-7697 https://orcid.org/0000-0003-2108-3004 https://orcid.org/0000-0003-2603-9694 http://dx.doi.org/10.1039/C8CP01159A Physical Chemistry Chemical Physics Creative Commons Attribution 3.0 unported license https://creativecommons.org/licenses/by/3.0/ application/pdf Royal Society of Chemistry (RSC) Royal Society of Chemistry (RSC) |
| spellingShingle | Buras, Zachary Chu, Te-Chun Jamal, Adeel Yee, Nathan Wa-Wai Middaugh, Joshua Eugene Green Jr, William H Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title | Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title_full | Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title_fullStr | Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title_full_unstemmed | Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title_short | Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation |
| title_sort | phenyl radical propene a prototypical reaction surface for aromatic catalyzed 1 2 hydrogen migration and subsequent resonance stabilized radical formation |
| url | http://hdl.handle.net/1721.1/120936 https://orcid.org/0000-0002-6797-8578 https://orcid.org/0000-0002-8475-7697 https://orcid.org/0000-0003-2108-3004 https://orcid.org/0000-0003-2603-9694 |
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