Gas-grain astrochemical model results for l-C₃H₃⁺, CH₃CCH, C₆H₄, C₆H₆, C₆H₅CN, and C₆H₅C₂H in dark clouds as a function of cloud age. Solid black line: standard network results. Solid red line: nominal network excluding the gas-phase C₆H₅⁺ + H₂ reaction. Solid blue line: nominal network excluding the gas-phase l-C₃H₃⁺ + H₂ reaction. Horizontal shaded rectangle: observed abundances in TMC-1 with an arbitrary error of ±2: l-C₃H₃⁺ Silva et al. (2023), CH₃CCH (Askne et al. 1983; Irvine et al. 1981; Markwick et al. 2002; Turner et al. 1999), C₆H₄ Cernicharo et al. (2021b), C₆H₅CN McGuire et al. (2018), and C₆H₅C₂H (Loru et al. 2023).