- Physical Review Journals
All JournalsPhysics Magazine

PRX Energy

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Comparative Study of Anisole and 4-Vinylanisole Pyrolysis: Insight into Char, Tar, and Particle Formation During Lignin Pyrolysis

Jas Shahanand1,*, Surjendu Bhattacharyya2, Alexander K. Lemmens2,3, Nureshan Dias3, Musahid Ahmed3,†, Thomas J. A. Wolf2, Ray P. Bambha1, and Hope A. Michelsen1,4,‡

  • *Contact author: Jas.Shahanand@colorado.edu
  • †Contact author: mahmed@lbl.gov
  • ‡Contact author: Hope.Michelsen@colorado.edu
PDF

PRX Energy 5, 023005 – Published 15 May, 2026

DOI: https://doi.org/10.1103/n1t9-l6zj

Abstract

Lignin pyrolysis generates oxygenated aromatics that can serve as renewable biofuel precursors. Anisole and substituted anisoles are widely used as model compounds to probe processes related to their production and use. We present a comparative study of anisole and 4-vinylanisole thermal decomposition using vacuum-ultraviolet photoionization mass spectrometry in a silicon carbide microreactor from 300 to 1300 K. For both molecular species, the initial decomposition pathway is O—CH3 bond cleavage. The vinyl substituent lowers the bond dissociation energy, shifting decomposition to lower temperatures for 4-vinylanisole. Anisole pyrolysis produces hydrogen-atom, methyl, propargyl, phenoxy, and cyclopentadienyl radicals, phenol, cyclopentadiene, cyclopentadienyl dimer, methylcyclopentadiene, CO, acetylene, and benzene via methylcyclopentadiene. The products of 4-vinylanisole pyrolysis include hydrogen-atom, methyl, propargyl, fulvenallenyl, vinylphenoxy, vinylcyclopentadienyl, and cyclopentadienyl radicals, vinylphenol, vinylcyclopentadiene, dimethylfulvene, fulvenallene, vinylacetylene, CO, and acetylene, but no benzene. Vinyl substitution thus facilitates resonance-stabilized radical (RSR) formation at temperatures lower than the cracking temperature of anisole. Whereas 4-vinylanisole decomposes at a lower temperature than anisole, both species produce significant RSR products that facilitate aromatic growth and gas-to-condensed-phase hydrocarbon conversion, in contrast to their methyl-substituted analog. These new insights into RSR formation are applicable to lignin pyrolysis and may be useful for limiting char or tar formation during biofuel production and for developing predictive models of emissions from smoldering and propagating flaming wildfires.

View figure in article

Physics Subject Headings (PhySH)

Popular Summary

Biomass provides an opportunity to produce sustainable carbon-neutral fuels. Lignin, one of the main components of biomass, poses significant challenges for conversion to biofuels, including char and tar formation. During pyrolysis, lignin decomposition yields aromatic products with alkyl, alkenyl, and methoxy side groups. Char and tar are more readily formed if the products include alkenyl side groups. These products are also likely to facilitate particle emissions during wildfires.

Effective lignin conversion requires a better understanding of lignin pyrolysis. Here, the authors investigated lignin pyrolysis using the model lignin pyrolysis product, anisole, and its alkenyl-substituted analog, 4-vinylanisole. They found that the alkenyl side group (vinyl) lowered the energy required for pyrolytic decomposition of 4-vinylanisole relative to anisole. Both model compounds produce predominantly resonance-stabilized radical (RSR) species known to lead to gas-to-condensed-phase hydrocarbon transitions through radical-chain reactions akin to polymerization, but 4-vinylanisole produces RSRs at lower temperatures than does anisole. The authors conclude that the RSR pyrolysis products lead to enhanced char/tar formation for the alkenyl-substituted lignin products over those with alkyl substituents. The vinyl-substituted species potentially enhance char/tar relative to the unsubstituted species by decomposing at lower temperatures.

Article Text

Supplemental Material

References (157)

  1. A. V. Bridgwater, Review of fast pyrolysis of biomass and product upgrading, Biomass Bioenergy 38, 68 (2012).
  2. D. Mohan, C. U. Pittman, and P. H. Steele, Pyrolysis of wood/biomass for bio-oil: A critical review, Energy Fuels 20, 848 (2006).
  3. A. Demirbaş, Biomass resource facilities and biomass conversion processing for fuels and chemicals, Energy Convers. Manage. 42, 1357 (2001).
  4. A. Akherati, Y. He, M. M. Coggon, A. R. Koss, A. L. Hodshire, K. Sekimoto, C. Warneke, J. de Gouw, L. Yee, J. H. Seinfeld, T. B. Onasch, S. C. Herndon, W. B. Knighton, C. D. Cappa, M. J. Kleeman, C. Y. Lim, J. H. Kroll, J. R. Pierce, and S. H. Jathar, Oxygenated aromatic compounds are important precursors of secondary organic aerosol in biomass-burning emissions, Environ. Sci. Technol. 54, 8568 (2020).
  5. Z. Fang, A. Lai, D. Cai, C. Li, R. Carmieli, J. Chen, X. Wang, and Y. Rudich, Secondary organic aerosol generation from biomass burning emitted phenolic compounds: Oxidative potential, reactive oxygen species, and cytotoxicity, Environ. Sci. Technol. 58, 8194 (2024).
  6. M. Breuer, K. A. Heufer, and M. Döntgen, Ab initio investigation of primary fuel reactions of monoaromatic hydrocarbons under pyrolytic conditions: Anisole, phenetole, and the 2-, 3-, 4-methylanisole isomers, J. Phys. Chem. A 129, 7700 (2025).
  7. K. A. Heufer, R. D. Büttgen, L. Pratali Maffei, and M. Pelucchi, Relative reactivity of methyl anisole isomers: An experimental and kinetic modelling study, Combust. Flame 266, 113533 (2024).
  8. C. Amen-Chen, H. Pakdel, and C. Roy, Production of monomeric phenols by thermochemical conversion of biomass: A review, Bioresour. Technol. 79, 277 (2001).
  9. A. J. Ragauskas, G. T. Beckham, M. J. Biddy, R. Chandra, F. Chen, M. F. Davis, B. H. Davison, R. A. Dixon, P. Gilna, M. Keller, P. Langan, A. K. Naskar, J. N. Saddler, T. J. Tschaplinski, G. A. Tuskan, and C. E. Wyman, Lignin valorization: improving lignin processing in the biorefinery, Science 344, 1246843 (2014).
  10. O. Faix, D. Meier, and I. Fortmann, Thermal degradation products of wood, Holz als Roh- und Werkstoff 48, 351 (1990).
  11. P. R. Patwardhan, R. C. Brown, and B. H. Shanks, Understanding the fast pyrolysis of lignin, ChemSusChem 4, 1629 (2011).
  12. O. Faix, I. Fortmann, J. Bremer, and D. Meier, Thermal degradation products of wood, Holz als Roh- und Werkstoff 49, 213 (1991).
  13. J. Ralph, C. Lapierre, and W. Boerjan, Lignin structure and its engineering, Curr. Opin. Biotechnol. 56, 240 (2019).
  14. A.-M. Saariaho, A.-S. Jääskeläinen, M. Nuopponen, and T. Vuorinen, Ultraviolet resonance Raman spectroscopy in lignin analysis: Determination of characteristic vibrations of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures, Appl. Spectrosc. 57, 58 (2003).
  15. C. Xu and F. Ferdosian, Conversion of Lignin into Bio-Based Chemicals and Materials (Springer, Berlin, Heidelberg, Germany, 2017), p. 13.
  16. D. L. Dalluge, K. H. Kim, and R. C. Brown, The influence of alkali and alkaline earth metals on char and volatile aromatics from fast pyrolysis of lignin, J. Anal. Appl. Pyrolysis 127, 385 (2017).
  17. A. V. Friderichsen, E.-J. Shin, R. J. Evans, M. R. Nimlos, D. C. Dayton, and G. B. Ellison, The pyrolysis of anisole (C3H5OCH3) using a hyperthermal nozzle, Fuel 80, 1747 (2001).
  18. N. Delort, I. Meziane, M. Framinet, R. Bounaceur, J. Bourgalais, F. Battin-Leclerc, and O. Herbinet, An experimental and modeling investigation of the combustion of anisole and guaiacol, Fuel 362, 130832 (2024).
  19. S. Zare, S. Roy, A. El Maadi, and O. Askari, An investigation on laminar burning speed and flame structure of anisole-air mixture, Fuel 244, 120 (2019).
  20. Y. Wu, B. Rossow, V. Modica, X. Yu, L. Wu, and F. Grisch, Laminar flame speed of lignocellulosic biomass-derived oxygenates and blends of gasoline/oxygenates, Fuel 202, 572 (2017).
  21. S. W. Wagnon, S. Thion, E. J. K. Nilsson, M. Mehl, Z. Serinyel, K. Zhang, P. Dagaut, A. A. Konnov, G. Dayma, and W. J. Pitz, Experimental and modeling studies of a biofuel surrogate compound: laminar burning velocities and jet-stirred reactor measurements of anisole, Combust. Flame 189, 325 (2018).
  22. C. S. Mergulhão, H.-H. Carstensen, H. Song, S. W. Wagnon, W. J. Pitz, and G. Vanhove, Probing the antiknock effect of anisole through an ignition, speciation and modeling study of its blends with isooctane, Proc. Combust. Inst. 38, 739 (2021).
  23. R. D. Büttgen, M. Tian, Y. Fenard, H. Minwegen, M. D. Boot, and K. A. Heufer, An experimental, theoretical and kinetic modelling study on the reactivity of a lignin model compound anisole under engine-relevant conditions, Fuel 269, 117190 (2020).
  24. K. Sood, S. Suzuki, K. Kobayashi, N. Tanishita, L. Gasnot, K. Tanaka, Y. Sakai, and L. S. Tran, Formation of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) in pyrolysis of 4–methylanisole and comparison with anisole, Fuel 405, 136396 (2026).
  25. K. Sood, A. Faccinetto, S. Gosselin, S. Suzuki, A. El Bakali, K. M. Van Geem, P. Desgroux, L. Gasnot, and L.-S. Tran, Study of the influence of anisole amounts and equivalence ratios on 1–3 ring aromatics in premixed flames near the sooting threshold, Fuel 392, 134831 (2025).
  26. K. Sood, S. Gosselin, A. E. Bakali, A. Faccinetto, P. Desgroux, K. M. Van Geem, L. Gasnot, and L.-S. Tran, Quantitative investigation of the formation of oxygenated aromatics in an anisole-doped flame, Proc. Combust. Inst. 40, 105289 (2024).
  27. W. Yuan, T. Li, Y. Li, M. Zeng, Y. Zhang, J. Zou, C. Cao, W. Li, J. Yang, and F. Qi, Experimental and kinetic modeling investigation on anisole pyrolysis: Implications on phenoxy and cyclopentadienyl chemistry, Combust. Flame 201, 187 (2019).
  28. C.-Y. Lin and M. C. Lin, Thermal decomposition of methyl phenyl ether in shock waves: The kinetics of phenoxy radical reactions, J. Phys. Chem. 90, 425 (1986).
  29. S. Zabeti, M. Aghsaee, M. Fikri, O. Welz, and C. Schulz, Optical properties and pyrolysis of shock-heated gas-phase anisole, Proc. Combust. Inst. 36, 4525 (2017).
  30. B. Chen, M. Hellmuth, S. Faller, L. May, P. Liu, L. Cai, W. L. Roberts, and H. Pitsch, Exploring the combustion chemistry of anisole in laminar counterflow diffusion-flames under oxy-fuel conditions, Combust. Flame 243, 111929 (2022).
  31. B. Chen, S. Kruse, R. Schmid, L. Cai, N. Hansen, and H. Pitsch, Oxygenated PAH formation chemistry investigation in anisole jet stirred reactor oxidation by a thermodynamic approach, Energy Fuels 35, 1535 (2021).
  32. I. W. C. E. Arends, R. Louw, and P. Mulder, Kinetic study of the thermolysis of anisole in a hydrogen atmosphere, J. Phys. Chem. 97, 7914 (1993).
  33. T. Bierkandt, P. Hemberger, P. Oßwald, D. Krüger, M. Köhler, and T. Kasper, Flame structure of laminar premixed anisole flames investigated by photoionization mass spectrometry and photoelectron spectroscopy, Proc. Combust. Inst. 37, 1579 (2019).
  34. M. Nowakowska, O. Herbinet, A. Dufour, and P.-A. Glaude, Detailed kinetic study of anisole pyrolysis and oxidation to understand tar formation during biomass combustion and gasification, Combust. Flame 161, 1474 (2014).
  35. T. Zhang, C. Bhattarai, Y. Son, V. Samburova, A. Khlystov, and S. A. Varganov, Reaction mechanisms of anisole pyrolysis at different temperatures: experimental and theoretical studies, Energy Fuels 35, 9994 (2021).
  36. M. Pecullan, K. Brezinsky, and I. Glassman, Pyrolysis and oxidation of anisole near 1000 K, J. Phys. Chem. A 101, 3305 (1997).
  37. V. V. Platonov, V. A. Proskuryakov, S. V. Ryl'tsova, and Y. N. Popova, Homogeneous pyrolysis of anisole, Russ. J. Appl. Chem. 74, 1047 (2001).
  38. Y. Koirala, Ph.D. thesis, Colorado School of Mines, 2015.
  39. B. Shu, J. Herzler, S. Peukert, M. Fikri, and C. Schulz, A shock tube and modeling study about anisole pyrolysis using time-resolved CO absorption measurements, Int. J. Chem. Kinet. 49, 656 (2017).
  40. A. M. Scheer, C. Mukarakate, D. J. Robichaud, G. B. Ellison, and M. R. Nimlos, Radical chemistry in the thermal decomposition of anisole and deuterated anisoles: An investigation of aromatic growth, J. Phys. Chem. A 114, 9043 (2010).
  41. R. H. Schlosberg, P. F. Szajowski, G. D. Dupre, J. A. Danik, A. Kurs, T. R. Ashe, and W. I. Olmstead, Pyrolysis studies of organic oxygenates, Fuel 62, 690 (1983).
  42. J. C. Mackie, K. R. Doolan, and P. F. Nelson, Kinetics of the thermal decomposition of methoxybenzene (anisole), J. Phys. Chem. 93, 664 (1989).
  43. L. Pratali Maffei, A. Della Libera, T. Faravelli, and C. Cavallotti, Theoretical and kinetic analysis of anisole and cresol primary reactivity in pyrolysis and combustion, Proc. Combust. Inst. 40, 105272 (2024).
  44. M. M. Suryan, S. A. Kafafi, and S. E. Stein, The thermal decomposition of hydroxy- and methoxy-substituted anisoles, J. Am. Chem. Soc. 111, 1423 (1989).
  45. M. H. Back, Comment on the thermal decomposition of anisole and the heat of formation of phenoxy radical, J. Phys. Chem. 93, 6880 (1989).
  46. G. Li, L. Li, L. Jin, Z. Tang, H. Fan, and H. Hu, Methyl substitution effect in pyrolysis of coal-based model compound isomers, Fuel Process. Technol. 178, 371 (2018).
  47. G. Li, L. Li, L. Shi, L. Jin, Z. Tang, H. Fan, and H. Hu, Experimental and theoretical study on the pyrolysis mechanism of three coal-based model compounds, Energy Fuels 28, 980 (2014).
  48. R. I. Kaiser, L. Zhao, W. Lu, M. Ahmed, M. V. Zagidullin, V. N. Azyazov, and A. M. Mebel, Formation of benzene and naphthalene through cyclopentadienyl-mediated radical-radical reactions, J. Phys. Chem. Lett. 13, 208 (2022).
  49. B. K. Carpenter, G. B. Ellison, M. R. Nimlos, and A. M. Scheer, A conical intersection influences the ground state rearrangement of fulvene to benzene, J. Phys. Chem. A 126, 1429 (2022).
  50. M. F. R. Mulcahy and D. J. Williams, Reactions of free radicals with aromatic compounds in the gaseous phase. II. Kinetics of the reaction of methyl radicals with phenol, Aust. J. Chem. 18, 20 (1965).
  51. M. Frenklach and H. Wang, Detailed modeling of soot particle nucleation and growth, Proc. Combust. Inst. 23, 1559 (1991).
  52. H. Wang and M. Frenklach, Calculations of rate coefficients for the chemically activated reactions of acetylene with vinylic and aromatic radicals, J. Phys. Chem. 98, 11465 (1994).
  53. F. Battin-Leclerc, N. Delort, I. Meziane, O. Herbinet, Y. Sang, and Y. Li, Possible use as biofuels of monoaromatic oxygenates produced by lignin catalytic conversion: A review, Catal. Today 408, 150 (2023).
  54. R. L. McCormick, M. A. Ratcliff, E. Christensen, L. Fouts, J. Luecke, G. M. Chupka, J. Yanowitz, M. Tian, and M. Boot, Properties of oxygenates found in upgraded biomass pyrolysis oil as components of spark and compression ignition engine fuels, Energy Fuels 29, 2453 (2015).
  55. M. M. Suryan, S. A. Kafafi, and S. E. Stein, Dissociation of substituted anisoles: Substituent effects on bond strengths, J. Am. Chem. Soc. 111, 4594 (1989).
  56. Y.-D. Wu and D. K. W. Lai, A density functional study of substituent effects on the O—H and O—CH3 bond dissociation energies in phenol and anisole, J. Org. Chem. 61, 7904 (1996).
  57. R. Li, T. Du, J. Liu, A. J. A. Aquino, and J. Zhang, Theoretical study of O—CH3 bond dissociation enthalpy in anisole systems, ACS Omega 6, 21952 (2021).
  58. T. Du, F. H. Quina, D. Tunega, J. Zhang, and A. J. A. Aquino, Theoretical O—CH3 bond dissociation enthalpies of selected aromatic and non-aromatic molecules, Theor. Chem. Acc. 139, 75 (2020).
  59. D. J. Clifford, D. M. Carson, D. E. McKinney, J. M. Bortiatynski, and P. G. Hatcher, A new rapid technique for the characterization of lignin in vasular plants: Thermochemolysis with tetramethylammonium hydroxide (TMAH), Org. Geochem. 23, 169 (1995).
  60. L. Chen, X. Ye, F. Luo, J. Shao, Q. Lu, Y. Fang, X. Wang, and H. Chen, Pyrolysis mechanism of ß-O-4 type lignin model dimer, J. Anal. Appl. Pyrolysis 115, 103 (2015).
  61. K. Kuroda, T. Ashitani, K. Fujita, and R. Hattori, Thermal behavior of ß-1 subunits in lignin: Pyrolysis of 1,2-diarylpropane-1,3-diol-type lignin model compounds, J. Agric. Food Chem. 55, 2770 (2007).
  62. L. Yin, E. Leng, X. Gong, Y. Zhang, and X. Li, Pyrolysis mechanism of ß-O-4 type lignin model polymers with different oxygen functional groups on Ca, J. Anal. Appl. Pyrolysis 136, 169 (2018).
  63. A. Dufour, J. Weng, L. Jia, X. Tang, B. Sirjean, R. Fournet, H. Le Gall, N. Brosse, F. Billaud, G. Mauviel, and F. Qi, Revealing the chemistry of biomass pyrolysis by means of tunable synchrotron photoionisation-mass spectrometry, RSC Adv. 3, 4786 (2013).
  64. X. Lu and X. Gu, A review on lignin pyrolysis: Pyrolytic behavior, mechanism, and relevant upgrading for improving process efficiency, Biotechnol Biofuels 15, 106 (2022).
  65. Molecule-of-the-Week Archive: 4-Vinylanisole, (American Chemical Society) https://www.acs.org/molecule-of-the-week/archive/v/4-vinylanisole.html
  66. X. Guo, Q. Yu, D. Chen, J. Wei, P. Yang, J. Yu, X. Wang, and L. Kang, 4-Vinylanisole is the aggregation pheromone in locusts, Nature 584, 584 (2020).
  67. J. Yang, Q. Yu, J. Yu, L. Kang, and X. Guo, 4-Vinylanisole promotes conspecific interaction and acquisition of gregarious behavior in the migratory locust, Proc. Natl. Acad. Sci. U.S.A. 120, e2306659120 (2023).
  68. X. Guo, L. Gao, S. Li, J. Gao, Y. Wang, J. Lv, J. Wei, J. Yang, H. Ke, Q. Ding, J. Yang, F. Guo, H. Zhang, X. Lei, and L. Kang, Decoding 4-vinylanisole biosynthesis and pivotal enzymes in locusts, Nature 644, 420 (2025).
  69. M. Gibernau, E. Gomes Gonçalves, A. Do Amaral Navarro, and A. Dália Maia, Chemical diversity of floral scents in 9 species of Philodendron (Araceae) from French Guiana, Bot. Lett. 170, 53 (2023).
  70. M. A. Díaz, E. Coy-Barrera, and D. Rodríguez, Attractive behavior and functional response of Orius insidiosus to semiochemicals mediating rose-western flower thrips interactions, Agriculture 15, 431 (2025).
  71. J. Ledauphin, C. Le Milbeau, D. Barillier, and D. Hennequin, Differences in the volatile compositions of French labeled brandies (Armagnac, Calvados, Cognac, and Mirabelle) using GC-MS and PLS-DA, J. Agric. Food Chem. 58, 7782 (2010).
  72. M. Jakubíková, J. Sádecká, and K. Hroboňová, Classification of plum brandies based on phenol and anisole compounds using HPLC, Eur. Food Res. Technol. 245, 1709 (2019).
  73. M. R. Tellez, I. A. Khan, B. T. Schaneberg, S. L. Crockett, A. M. Rimando, and M. Kobaisy, Steam distillation-solid-phase microextraction for the detection of Ephedra sinica in herbal preparations, J. Chromatogr. A 1025, 51 (2004).
  74. Q. Wang, Y. Yang, X. Zhao, B. Zhu, P. Nan, J. Zhao, L. Wang, F. Chen, Z. Liu, and Y. Zhong, Chemical variation in the essential oil of Ephedra sinica from Northeastern China, Food Chem. 98, 52 (2006).
  75. A. T. Alade, S. O. Aboaba, P. Satyal, and W. N. Setzer, Chemical constituents, antioxidant activities and antimicrobial properties of volatile oil from different part of Duranta repens Linn, Am. J. Essent. Oil. Nat. Prod. 9, 6 (2021).
  76. E.-J. Brunke, F.-J. Hammerschmidt, and G. Schmaus, Scent of roses: Recent results, Flavour Fragr. J. 7, 195 (1992).
  77. S. Nakamura, Scent and component analysis of the hybrid tea rose, P&F 12, 43 (1987).
  78. D. Feng, H. Jian, H. Zhang, X. Qiu, Z. Wang, W. Du, L. Xie, Q. Wang, N. Zhou, H. Wang, K. Tang, and H. Yan, Comparison of volatile compounds between wild and cultivated roses, HorScience 57, 657 (2022).
  79. Y. Tao, J. He, Z. Wang, J. Pan, H. Jiang, S. Chen, and Y. Yang, Synthesis of branched polystyrene and poly(styrene-b-4-methoxystyrene) by nitroxyl stable radical controlled polymerization, Macromolecules 34, 4742 (2001).
  80. H. Yoshioka, K. Yamaguchi, and M. Kobayashi, Deviant polymerization behavior of 4-acetoxystyrene found through a detailed study on the ATRP of para-substituted styrenes, Polym. J. 51, 627 (2019).
  81. J.-C. Daigle, A. Vijh, P. Hovington, C. Gagnon, J. Hamel-Pâquet, S. Verreault, N. Turcotte, D. Clément, A. Guerfi, and K. Zaghib, Lithium battery with solid polymer electrolyte based on comb-like copolymers, J. Power Sources 279, 372 (2015).
  82. A. D. Hendricker, F. Basile, and K. J. Voorhees, A study of protein oxidative products using a pyrolysis-membrane inlet quadrupole ion trap mass spectrometer with air as the buffer gas, J. Anal. Appl. Pyrolysis 46, 65 (1998).
  83. H. Jin, L. Xing, D. Liu, J. Hao, J. Yang, and A. Farooq, First aromatic ring formation by the radical-chain reaction of vinylacetylene and propargyl, Combust. Flame 225, 524 (2021).
  84. R. McClish, M. R. Bentley, M. Muse, G. H. Jones, P. R. Franke, D. Schlier, P. Hemberger, A. Bodi, G. B. Ellison, J. F. Stanton, and J. Bouwman, Unpublished (2026).
  85. J. D. Savee, T. M. Selby, O. Welz, C. A. Taatjes, and D. L. Osborn, Time- and isomer-resolved measurements of sequential addition of acetylene to the propargyl radical, J. Phys. Chem. Lett. 6, 4153 (2015).
  86. L. Zhao, T. Yang, R. I. Kaiser, T. P. Troy, B. Xu, M. Ahmed, J. Alarcon, D. Belisario-Lara, A. M. Mebel, Y. Zhang, C. Cao, and J. Zou, A vacuum ultraviolet photoionization study on high-temperature decomposition of JP-10 (exo-tetrahydrodicyclopentadiene), Phys. Chem. Chem. Phys. 19, 15780 (2017).
  87. P. A. Heimann, M. Koike, C. W. Hsu, D. Blank, X. M. Yang, A. G. Suits, Y. T. Lee, M. Evans, C. Y. Ng, C. Flaim, and H. A. Padmore, Performance of the vacuum ultraviolet high-resolution and high-flux beamline for chemical dynamics studies at the Advanced Light Source, Rev. Sci. Instrum. 68, 1945 (1997).
  88. Q. Guan, K. N. Urness, T. K. Ormond, D. E. David, G. Barney Ellison, and J. W. Daily, The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules, Int. Rev. Phys. Chem. 33, 447 (2014).
  89. F. Zhang, R. I. Kaiser, V. V. Kislov, A. M. Mebel, A. Golan, and M. Ahmed, A VUV photoionization study of the formation of the indene molecule and its isomers, J. Phys. Chem. Lett. 2, 1731 (2011).
  90. F. Zhang, R. I. Kaiser, A. Golan, M. Ahmed, and N. Hansen, A VUV photoionization study of the combustion-relevant reaction of the phenyl radical (C6H5) with propylene (C3H6) in a high temperature chemical reactor, J. Phys. Chem. A 116, 3541 (2012).
  91. M. V. Zagidullin, R. I. Kaiser, D. P. Porfiriev, I. P. Zavershinskiy, M. Ahmed, V. N. Azyazov, and A. M. Mebel, Functional relationships between kinetic, flow, and geometrical parameters in a high-temperature chemical microreactor, J. Phys. Chem. A 122, 8819 (2018).
  92. P. Hemberger, X. Wu, Z. Pan, and A. Bodi, Continuous pyrolysis microreactors: Hot sources with little cooling? New insights utilizing cation velocity map imaging and threshold photoelectron spectroscopy, J. Phys. Chem. A 126, 2196 (2022).
  93. LennoxLaser.com/capabilities/orifice-calculator.
  94. P. Chen, S. D. Colson, W. A. Chupka, and J. A. Berson, Flash pyrolytic production of rotationally cold free radicals in a supersonic jet. Resonant multiphoton spectrum of the 3p2A2 “.raw. X2A2” origin band of methyl, J. Phys. Chem. 90, 2319 (1986).
  95. H. W. Rohrs, C. T. Wickham-Jones, G. B. Ellison, D. Berry, and B. M. Argrow, Fourier transform infrared absorption spectroscopy of jet-cooled radicals, Rev. Sci. Instrum. 66, 2430 (1995).
  96. A. K. Vasiliou, K. M. Piech, B. Reed, X. Zhang, M. R. Nimlos, M. Ahmed, A. Golan, O. Kostko, D. L. Osborn, D. E. David, K. N. Urness, J. W. Daily, J. F. Stanton, and G. B. Ellison, Thermal decomposition of CH3CHO studied by matrix infrared spectroscopy and photoionization mass spectroscopy, J. Chem. Phys. 137, 164308 (2012).
  97. A. Vasiliou, M. R. Nimlos, J. W. Daily, and G. B. Ellison, Thermal decomposition of furan generates propargyl radicals, J. Phys. Chem. A 113, 8540 (2009).
  98. Q. Guan, G. B. Ellison, J. W. Daily, J. Stanton, and M. Ahmed, in 54th AIAA Aerospace Sciences Meeting (American Institute of Aeronautics and Astronautics, San Diego, California, 2016).
  99. A. Golan and M. Ahmed, Molecular beam mass spectrometry with tunable vacuum ultraviolet (VUV) synchrotron radiation, J. Visualized Exp. 68, e50164 (2012).
  100. J. D. Savee, B. Sztáray, P. Hemberger, J. Zádor, A. Bodi, and D. L. Osborn, Unimolecular isomerization of 1,5-hexadiyne observed by threshold photoelectron photoion coincidence spectroscopy, Faraday Discuss. 238, 645 (2022).
  101. See the Supplemental Material at http://link.aps.org/supplemental/10.1103/n1t9-l6zj for additional information related to the data analysis presented here.
  102. J. Huang, X. Wu, Q. Hou, M. Wu, J. Yang, and F. Zhang, Molecular orbital insight into the near-threshold photionization cross sections of monocyclic substituted aromatic compounds, Energy Fuels 35, 14051 (2021).
  103. T. A. Cool, K. Nakajima, C. A. Taatjes, A. McIlroy, P. R. Westmoreland, M. E. Law, and A. Morel, Studies of a fuel-rich propane flame with photoionization mass spectrometry, Proc. Combust. Inst. 30, 1681 (2005).
  104. P. C. St John, Y. Guan, Y. Kim, S. Kim, and R. S. Paton, Prediction of organic homolytic bond dissociation enthalpies at near chemical accuracy with sub-second computational cost, Nat. Commun. 11, 2328 (2020).
  105. P. C. St John, Y. Guan, Y. Kim, B. D. Etz, S. Kim, and R. S. Paton, Quantum chemical calculations for over 200,000 organic radical species and 40,000 associated closed-shell molecules, Sci. Data 7, 244 (2020).
  106. S. Sowndarya, S. V, Y. Kim, S. Kim, P. C. St John, and R. S. Paton, Expansion of bond dissociation prediction with machine learning to medicinally and environmentally relevant chemical space, Digit Discov. 2, 1900 (2023).
  107. alfabet: A machine-learning fast accurate bond dissociation enthalpy tool, https://huggingface.co/spaces/patonlab/alfabet_bde.
  108. I. P. WaveMetrics, Lake Oswego, Oregon.
  109. J. Shahanand, S. Bhattacharyya, A. K. Lemmens, N. Dias, M. Ahmed, T. J. A. Wolf, R. P. Bambha, and H. A. Michelsen, (Zenodo, 2025), https://doi.org/10.5281/zenodo.17561448
  110. W. Li, Y.-F. Zhang, C.-Y. Wang, J.-Z. Yang, M.-G. Xu, and L. Zhao, VUV photoionization study of the gas formation of the indene-A molecular building block of nonplanar PAHs, J. Phys. Chem. A 129, 10951 (2025).
  111. C. A. Taatjes, D. L. Osborn, T. M. Selby, G. Meloni, A. J. Trevitt, E. Epifanovsky, A. I. Krylov, B. Sirjean, E. Dames, and H. Wang, Products of the benzene + O(3P) reaction, J. Phys. Chem. A 114, 3355 (2010).
  112. Z. Pan, A. Puente-Urbina, A. Bodi, J. A. van Bokhoven, and P. Hemberger, Isomer-dependent catalytic pyrolysis mechanism of the lignin model compounds catechol, resorcinol and hydroquinone, Chem. Sci. 12, 3161 (2021).
  113. D. S. Parker, R. I. Kaiser, T. P. Troy, O. Kostko, M. Ahmed, and A. M. Mebel, Toward the oxidation of the phenyl radical and prevention of PAH formation in combustion systems, J. Phys. Chem. A 119, 7145 (2015).
  114. C. Fernholz, A. Bodi, and P. Hemberger, Threshold photoelectron spectrum of the phenoxy radical, J. Phys. Chem. A 126, 9022 (2022).
  115. H. Xu and S. T. Pratt, Photodissociation of anisole and absolute photoionization cross-section of the phenoxy radical, J. Phys. Chem. A 117, 12075 (2013).
  116. P. Hemberger, A. Bodi, T. Bierkandt, M. Köhler, D. Kaczmarek, and T. Kasper, Photoelectron photoioin coincidence spectroscopy provides mechanistic insights in fuel synthesis and conversion, Energy Fuels 35, 16265 (2021).
  117. N. Hansen, S. J. Klippenstein, J. A. Miller, J. Wang, T. A. Cool, M. E. Law, P. R. Westmoreland, T. Kasper, and K. Kohse-Höinghaus, Identification of C5Hx isomers in fuel-rich flames by photoionization mass spectrometry and electronic structure calculations, J. Phys. Chem. A 110, 4376 (2006).
  118. O. Herbinet, A. Rodriguez, B. Husson, F. Battin-Leclerc, Z. Wang, Z. Cheng, and F. Qi, Study of the formation of the first aromatic rings in the pyrolysis of cyclopentene, J. Phys. Chem. A 120, 668 (2016).
  119. J. D. Savee, S. Soorkia, O. Welz, T. M. Selby, C. A. Taatjes, and D. L. Osborn, Absolute photoionization cross-section of the propargyl radical, J. Chem. Phys. 136, 134307 (2012).
  120. J. D. Savee, O. Welz, C. A. Taatjes, and D. L. Osborn, New mechanistic insights to the O(3P) + propene reaction from multiplexed photoionization mass spectrometry, Phys. Chem. Chem. Phys. 14, 10410 (2012).
  121. B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) Values Based on Ver. 1.220 of the Thermochemical Network (Argonne National Laboratory, Lemont, Illinois, 2025).
  122. B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszevski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to active thermochemical tables: Several “key” enthalpies of formation revisited, J. Phys. Chem. 108, 9979 (2004).
  123. B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active thermochemical tables: Thermochemistry for the 21st century, J. Phys.: Conf. Ser. 16, 561 (2005).
  124. D. A. Pratt, M. I. de Heer, P. Mulder, and K. U. Ingold, Oxygen-carbon bond dissociation enthalpies of benzyl phenyl ethers and anisoles. An example of temperature dependent substituent effects, J. Am. Chem. Soc. 123, 5518 (2001).
  125. P. Mulder, H.-G. Korth, D. A. Pratt, G. A. DiLabio, L. Valgimigli, G. F. Pedulli, and K. U. Ingold, Critical re-evaluation of the O—H bond dissociation enthalpy in phenol, J. Phys. Chem. A 109, 2647 (2005).
  126. C. Y. Lin and M. C. Lin, Unimolecular decomposition of the phenoxy radical in shock waves, Int. J. Chem. Kinet. 17, 1025 (1985).
  127. NIST Chemistry WebBook, NIST Standard Reference Database Number 69.
  128. E. Hedaya, The techniques of flash vacuum pyrolysis. The cyclopentadienyl radical and its dimer, Acc. Chem. Res. 2, 367 (1969).
  129. J. Filley and J. T. McKinnon, Dimerization of cyclopentadienyl radical to produce naphthalene, Combust. Flame 124, 721 (2001).
  130. V. D. Knyazev and K. V. Popov, Kinetics of the self reaction of cyclopentadienyl radicals, J. Phys. Chem. A 119, 7418 (2015).
  131. N. Hansen, N. Gaiser, T. Bierkandt, P. Oßwald, M. Köhler, J. Zádor, and P. Hemberger, Identification of dihydropentalenes as products of the molecular-weight growth reaction of cyclopentadienyl plus propargyl, J. Phys. Chem. A 129, 1714 (2025).
  132. A. M. Mebel and V. V. Kislov, Can the C5H5 + C5H5 →C10H10 → C10H9 + H/C10H8 + H2 reaction produce naphthalene? An ab initio/RRKM study, J. Phys. Chem. A 113, 9825 (2009).
  133. A. E. Long, S. S. Merchant, A. G. Vandeputte, H.-H. Carstensen, A. J. Vervust, G. B. Marin, K. M. Van Geem, and W. H. Green, Pressure dependent kinetic analysis of pathways to naphthalene from cyclopentadienyl recombination, Combust. Flame 187, 247 (2018).
  134. R. A. Mackie, S. W. J. Scully, A. M. Sands, R. Browning, K. F. Dunn, and C. J. Latimer, A photoionization mass spectrometric study of acetylene and ethylene in the VUV spectral region, Int. J. Mass Spectrom. 223–224, 67 (2003).
  135. Z. Zhang, J. Pérez-Ramírez, J. A. van Bokhoven, A. Bodi, and P. Hemberger, Operando photoelectron photoion coincidence spectroscopy to detect short-lived intermediates in catalysis, Chimia 77, 132 (2023).
  136. J. A. Miller and S. J. Klippenstein, The recombination of propargyl radicals: Solving the master equation, J. Phys. Chem. A 105, 7254 (2001).
  137. J. A. Miller and S. J. Klippenstein, The recombination of propargyl radicals and other reactions on a C6H6 potential, J. Phys. Chem. A 107, 7783 (2003).
  138. M. H. Palmer, S. V. Hoffmann, N. C. Jones, M. Coreno, M. de Simone, C. Grazioli, R. A. Aitken, and I. L. J. Patterson, The singlet excited states of fulvene and of its 6,6-dimethyl derivative: A combined study of their energy levels by absorption spectroscopy, configuration interaction, and density functional calculations, J. Chem. Phys. 163, 024323 (2025).
  139. G. T. Buckingham, T. K. Ormond, J. P. Porterfield, P. Hemberger, O. Kostko, M. Ahmed, D. J. Robichaud, M. R. Nimlos, J. W. Daily, and G. B. Ellison, The thermal decomposition of the benzyl radical in a heated micro-reactor. I. Experimental findings, J. Chem. Phys. 142, 044307 (2015).
  140. W. Li, Y.-F. Zhang, J.-B. Huang, C.-Y. Wang, F. Zhang, J.-Z. Yang, and L. Zhao, A VUV photoionization study on the gas-phase synthesis of the first five-membered carbon ring - C7H6 isomers, Chem. Phys. Lett. 835, 140978 (2024).
  141. H. Jin, J. Hao, J. Yang, J. Guo, Y. Zhang, C. Cao, and A. Farooq, Experimental and kinetic modeling study of α-methyl-naphthalene pyrolysis: Part 1. Formation of monocyclic aromatics and small species, Combust. Flame 233, 111587 (2021).
  142. T. A. Cool, J. Wang, K. Nakajima, C. A. Taatjes, and A. Mcllroy, Photoionization cross sections for reaction intermediates in hydrocarbon combustion, Int. J. Mass Spectrom. 247, 18 (2005).
  143. J. Shahanand, S. Bhattacharyya, A. K. Lemmens, N. Dias, M. Ahmed, T. J. A. Wolf, R. P. Bambha, and H. A. Michelsen, (Zenodo, 2026), https://doi.org/10.5281/zenodo.19394595.
  144. Z. Pan, A. Bodi, J. A. van Bokhoven, and P. Hemberger, On the absolute photoionization cross section and threshold photoelectron spectrum of two reactive ketenes in lignin valorization: Fulvenone and 2-carbonyl cyclohexadienone, Phys. Chem. Chem. Phys. 24, 3655 (2022).
  145. Y. Zhao, P. Huang, L. Li, Y. Zhan, K. Wang, H. Yang, J. Jin, Y. Chen, Y. Liu, L. Sheng, J. Chen, and M. Cao, Vacuum ultraviolet photoionization and dissociative photoionization of toluene: Experimental and theoretical insights, Eur. J. Mass Spectrom. 27, 166 (2021).
  146. Z. Zhou, M. Xie, Z. Wang, and F. Qi, Determination of absolute photoionization cross-sections of aromatics and aromatic derivatives, Rapid Commun. Mass Spectrom. 23, 3994 (2009).
  147. H. Fu, Y. Wang, B. Liu, Z. Wang, X. Zhang, and G. Liu, Experimental and theoretical study of cyclopropanated fuel exo, exo-tetracyclo[3.3.1.02,4.06,8]nonane pyrolysis in a jet-stirred reactor, Fuel 361, 130702 (2024).
  148. K. N. Houk, J. K. George, and R. E. J. Duke, A frontier molecular orbital treatment of fulvene cycloadditions: Molecular orbital calculations and photoelectron spectra of substituted fulvenes, Tetrahedron 30, 523 (1974).
  149. K. O. Johansson, M. P. Head-Gordon, P. E. Schrader, K. R. Wilson, and H. A. Michelsen, Resonance-stabilized hydrocarbon-radical chain reactions may explain soot inception and growth, Science 361, 997 (2018).
  150. J. A. Rundel, K. O. Johansson, P. E. Schrader, R. P. Bambha, K. R. Wilson, J. Zádor, G. B. Ellison, and H. A. Michelsen, Production of aliphatic-linked polycyclic hydrocarbons during radical-driven particle formation from propyne and propene pyrolysis, Combust. Flame 258, 112457 (2023).
  151. J. A. Rundel, C. Martí, J. Zádor, P. E. Schrader, K. O. Johansson, R. P. Bambha, G. T. Buckingham, J. P. Porterfield, O. Kostko, and H. A. Michelsen, The identity and chemistry of C7H7 radicals observed during soot formation, J. Phys. Chem. A 127, 3000 (2023).
  152. J. A. Rundel, C. M. Thomas, P. E. Schrader, K. R. Wilson, K. O. Johansson, R. P. Bambha, and H. A. Michelsen, Promotion of particle formation by resonance-stabilized radicals during hydrocarbon pyrolysis, Combust. Flame 243, 111942 (2022).
  153. C. Martí, H. A. Michelsen, H. N. Najm, and J. Zádor, Comprehensive kinetics on the C7H7 potential energy surface under combustion conditions, J. Phys. Chem. A 127, 1941 (2023).
  154. Y. Ma, Y. Deng, Z. Xiong, J. Guo, L. Zhao, M. Zeng, W. Yuan, and F. Qi, Experimental and computational investigation of benzofuran decomposition kinetics, J. Phys. Chem. A 130, 275 (2026).
  155. K. Sekimoto, A. R. Koss, J. B. Gilman, V. Selimovic, M. M. Coggon, K. J. Zarzana, B. Yuan, B. M. Lerner, S. S. Brown, C. Warneke, R. J. Yokelson, J. M. Roberts, and J. de Gouw, High- and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels, Atmos. Chem. Phys. 18, 9263 (2018).
  156. J. Hendrix, D. Hait, H. A. Michelsen, and M. P. Head-Gordon, Hydrogen ejection from hydrocarbons: Characterization and relevance in soot formation and interstellar chemistry, Proc. Natl. Acad. Sci. U.S.A. 121, e2202744121 (2024).
  157. E. B. Hemings, G. Bozzano, M. Dente, and E. Ranzi, Detailed kinetics of the pyrolysis and oxidation of anisole, Chem. Eng. Trans. 24, 61 (2011).

Outline

Information

PRX Energy 5, 023005– Published 15 May, 2026
  • Received 9 November 2025
  • Revised 4 April 2026
  • Accepted 14 April 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation