Electrophilic reactivity of amino group for indicating sulfadiazines oxidation: Insights on the selective oxidation and conversion of singlet oxygen

This work elucidated the mechanism of selective oxidation and conversion between singlet oxygen ( 1 O 2 ) and sulfadiazine structures (SDs) by introducing local descriptors in the density functional theory . Based on the kinetic method , the quantitative structure-activity relationship (QSAR) between the molecular structure and the oxidation rates of reactive species (RSs) in peroxymonosulfate activation system to SDs was established. Results indicate that the second-order reaction rate of 1 O 2 , rather than the radicals, is well correlated with the electrophilic reactivity of the local amino group in the SDs (e.g., Fukui index and local nucleophilicity , Mantel’r = 0. 836 ∼ 0.998), while the overall descriptors are weak (e.g., E HOMO and ionization potential). Besides, the transformation of SDs to SO 2 extrusion products or aniline nitrated products depends not only on the RSs involved, but this electrophilic reactivity. The study advances the application of local descriptors in QSAR analysis and reveals the oxidation differences among RSs. • The local descriptors were introduced into the QSAR model. • Mantel analysis was conducted to establish correlations for k SO4 •- /•OH/ 1 O2, SDs . • The k 1 O2, SDs was positively correlated to electrophilicity of -NH 2 on SDs. • Speciated forms in alkaline was found not to affect the validity of this model. • 1 O 2 was identified in driving the nitroxylation transformation by HRLC-MS.