Fragmentation Dynamics of Benzoyl Peroxide: Insights from Rotational Spectroscopy.

Area of Science:

• Physical Chemistry
• Molecular Spectroscopy
• Computational Chemistry

Background:

• Benzoyl peroxide (BPO) is a widely used organic peroxide with industrial and pharmaceutical applications.
• Despite its prevalence, a detailed molecular-level understanding of BPO's thermal instability is lacking.
• Existing knowledge gaps hinder precise hazard assessments and rational design of peroxide-based systems.

Purpose of the Study:

• To perform the first gas-phase rotational spectroscopy characterization of isolated benzoyl peroxide (BPO).
• To elucidate the molecular structure and identify stabilizing interactions within BPO.
• To investigate BPO's photofragmentation pathways and understand its thermal resilience.

Main Methods:

• Laser ablation and supersonic jet expansion techniques for gas-phase BPO generation.
• Rotational spectroscopy for high-resolution molecular structure determination.
• Quantum chemical calculations and topological analysis for interaction identification.

Main Results:

• Determined the C₂-symmetric gas-phase structure of BPO, consistent with crystallographic data.
• Identified a stabilizing reciprocal n→π* interaction between adjacent carbonyl groups.
• Observed photofragmentation products including benzoic acid, benzyne, benzaldehyde, and benzophenone.

Conclusions:

• The study provides the first molecular-level insights into isolated BPO's structure and stability.
• The identified n→π* interaction may explain BPO's relative thermal resilience.
• Understanding decomposition pathways aids in safer handling and design of peroxide-based materials.