Insights Into Bifenthrin Stereoisomers and Their Regulatory Implications.

Bifenthrin (BF) is a synthetic pyrethroid insecticide extensively applied in agricultural and urban pest control. The molecular structure contains two stereogenic centers, giving rise to four stereoisomers with distinct physicochemical, electronic, and biological properties. However, many regulatory frameworks still consider BF as a single racemic active substance. Herein, we present a comprehensive structural and theoretical investigation of BF, integrating solid-state analysis with electronic structure calculations based on density functional theory. Also, supramolecular arrangements were analyzed using Hirshfeld surface, quantum theory of atoms in molecules, and natural bond orbital approaches. In parallel, global and local reactivity descriptors were evaluated through frontier molecular orbital analysis, molecular electrostatic potential mapping, and Fukui indices. Finally, the findings reveal stereoelectronic differences among the BF stereoisomers, with the 1S,3S isomer displaying a markedly anisotropic charge distribution and enhanced electronic reactivity, thereby underscoring the importance of incorporating stereochemical knowledge into pesticide risk assessment.