Experimental evidence for indene formation from o-methylphenyl radical + C2H2/C2H4 reactions

An experimental study was conducted to investigate the weight growth routes from o -methylphenyl radical ( o -CH 3 C 6 H 4 ) to indene. o -Nitrosotoluene served as the precursor for o -methylphenyl radicals in this study. Co-pyrolysis of o -methylphenyl radical/C 2 H 2 and o -methylphenyl radical/C 2 H 4 was investigated utilizing the chemical microreactor and synchrotron vacuum ultraviolet photoionization mass spectrometry. Sampled mass-specific photoionization efficiency (PIE) curves were employed to identify the aromatic species, elucidating interactions between o -methylphenyl radicals and C 2 species. The species detected at m/z = 116 and 118, essential for understanding the reaction mechanism, were identified via matching photoionization cross-sections and adiabatic ionization energies with literature and theoretical values. Specifically, indene and its isomer o -methylphenylacetylene ( m/z = 116) were determined in the reaction of o -methylphenyl radical with C 2 H 2 , while indene and o -methylstyrene ( m/z = 118) were identified in the reaction of o -methylphenyl radical with C 2 H 4 . By combining the identified intermediate species with previous literature basis, the formation pathways for indene, originating from o -methylphenyl radical were discussed in both reaction systems, providing further insights for understanding the indene formation pathways.