Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air-water interface is needed. This work shows how catechol -a molecular probe of the oxygenated aromatic hydrocarbons present in SOA- can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon the encounter of 40 ppbv - 6.0 ppmv O3(g) with microdroplets containing [catechol] = 1-150 μM. While the previous pathway results in the instantaneous formation of mono- and poly-hydroxylated aromatic rings (PHA) and chromophoric mono- and poly-hydroxylated quinones (PHQ), a different channel produces oxo- and di-carboxylic acids of low molecular weight (LMW). The cleavage of catechol occurs at the 1,2-carbon-carbon bond at the air-water interface through the formation of 1) an ozonide intermediate, 2) an hydroperoxide, and 3) cis,cis-muconic acid. However, variable [catechol] and [O3(g)] can affect the ratio of the primary products (cis,cis-muconic acid and trihydroxybenzenes) and higher-order products observed (PHA, PHQ, and LMW oxo- and di-carboxylic acids). Secondary processing is confirmed by mass spectrometry measurements showing the production of crotonic, maleinaldehydic, maleic, glyoxylic, and oxalic acids. The proposed pathway can contribute precursors to aqueous SOA formation converting aromatic hydrocarbons into polyfunctional species widely found in tropospheric aerosols with light-absorbing brown carbon.