Free electron mediated conversion of toluene into acetylene

Abstract

Toluene, a prevalent aromatic volatile organic compound (VOC), is an important target for simultaneous pollutant abatement and chemical valorization. Its selective conversion to acetylene is of particular interest because acetylene is a versatile industrial feedstock. Here, we demonstrate a previously unrecognized pathway for the selective conversion of toluene to acetylene through low-energy (≤500 eV) electron-induced chemistry under cryogenic conditions (15 K). The decomposition of toluene was investigated using Fourier transform infrared spectroscopy and temperature-programmed desorption mass spectrometry. Electron irradiation appears to selectively generate benzyl radicals (C6H5CH2•) as key intermediates, which subsequently decompose into cyclopentadienyl radicals (C5H5•) and acetylene (C2H2). Our findings indicate that low-energy free electrons drive a low-barrier, benzyl-radical-mediated fragmentation pathway while effectively suppressing competing rearrangements and bimolecular reactions. This work provides crucial molecular-level insights into electron-driven VOC degradation, highlighting the viability of controlled electron irradiation for simultaneous environmental remediation and value-added chemical synthesis.