Prediction of the relative abundance of benzonitrile (C₆H₅CN) as a function of time in the chemical model of TMC-1. The solid black line is the abundance predicted by the model before including the ring expansion mechanisms, and the dashed lines represents how it is modified when considering the formation of the six-membered rings for two possible reaction rate constants, 10⁻⁹ (green) and 10⁻¹⁰ (red); see the main text. The horizontal dotted line represents the observed abundance of benzonitrile in TMC-1 (Cernicharo et al. 2021c).