“…However, the elucidation of the fundamental reaction pathways to polycyclic aromatic hydrocarbons (PAHs)—organic molecules composed of fused benzene rings with naphthalene (C 10 H 8 ) denoting the simplest representative—in combustion environments 1 and in the interstellar medium (ISM) 2 has posed a long-standing challenge. Sophisticated combustion 3 and astrochemical reaction networks 4 along with flame sampling studies 5 and astronomical surveys 2 reveal that PAHs represent the critical link between resonantly stabilized free radicals (RSFRs) like propargyl (C 3 H 3 • ), allyl (C 3 H 5 • ), and cyclopentadienyl (C 5 H 5 • ) 6,7 and carbonaceous nanoparticles universally referred to as soot and interstellar grains on Earth and in extraterrestrial environments, respectively 2,8,9 . Whereas on Earth, PAHs represent undesirable toxic, often carcinogenic byproducts released in incomplete combustion 10 , in the interstellar medium, PAHs embody up to 20% of the galactic carbon budget 11 and are—along with carbonaceous grains—suggested to play a central role in the formation of vital precursors to molecular building blocks of life such as amino acids 8 .…”