Kinetic study of the CN radical reaction with 2-methylfuran

The gas phase reaction of the ground state cyano-radical (CN (X²∑⁺)) with 2-methylfuran (2-MF) is investigated in a quasi-static reaction cell at pressures ranging from 2.2 to 7.6 Torr and temperatures ranging from 304 to 440 K. The CN radicals are generated in their ground electronic state by pulsed laser photolysis of gaseous cyanogen iodide (ICN) at 266 nm. Their concentration is monitored as a function of reaction time using laser-induced fluorescence at 387.3 nm on the B²∑⁺ (ν′ = 0) ← X²∑⁺ (ν″ = 0) vibronic band. The reaction rate coefficient is found to be rapid and independent of pressure and temperature. Over the investigated temperature and pressure ranges, the rate coefficient is measured to be 2.83 (± 0.18) × 10⁻¹⁰ cm³ molecules s⁻¹. The enthalpies of the stationary points and transition states on the CN + 2-MF potential energy surface are calculated using the CBS-QB3 computational method. The kinetic results suggest the lack of a prereactive complex on the reaction entrance channel with either a very small or nonexistent entrance energy barrier. In addition, the potential energy surface calculations reveal only submerged barriers along the minimum energy path. Based on comparisons between previous CN reactions with unsaturated hydrocarbons, the most likely reaction pathway is CN addition onto one of the unsaturated carbons followed by either H or methyl elimination. The implications for the transformation of biomass-derived fuels in nitrogen-rich flames is discussed.