Fragmentation Dynamics of Benzoyl Peroxide: Insights from Rotational Spectroscopy

Benzoyl peroxide (BPO) represents a structurally simple yet hazardous organic peroxide with widespread applications across industrial and pharmaceutical domains. Despite its extensive use, detailed molecular-level understanding of its thermal instability remains limited. Here, we present the first rotational spectroscopy characterization of isolated BPO in the gas phase, enabled by laser ablation and supersonic jet expansion techniques. Our analysis reveals a C₂-symmetric structure with quasi-perpendicular aromatic rings, in excellent agreement with crystallographic data. Quantum chemical calculations and topological analysis identify a stabilizing reciprocal n→π* interaction between adjacent carbonyl groups that may contribute to BPO's thermal resilience compared to other organic peroxides. Furthermore, we detect several photofragmentation products, including benzoic acid, benzyne, benzaldehyde, and benzophenone, providing insights into potential decomposition pathways. This molecular-level investigation bridges the gap between macroscopic hazard assessments and fundamental understanding of peroxide reactivity, with implications for safer handling and rational design of peroxide-based systems.