Product and mechanistic insights into the ozonolysis of Δ3-Carene

Abstract

This study combines experimental and theoretical approaches to investigate the gas-phase ozonolysis of Δ³-carene, with a focus on product identification and mechanistic elucidation. Atmospheric ozonolysis was simulated using both a Teflon chamber and a jet-stirred reactor. Product characterization was achieved through vacuum ultraviolet photoionization mass spectrometry employing soft ionization techniques, combined with Hefei synchrotron radiation to acquire mass-selected photoionization efficiency spectra of Δ³-carene and its ozonolysis products. Structural assignments were then facilitated by theoretical calculations conducted at the M06-2X/6–311++G(d,p) level of theory. Our analysis revealed many characteristic ozonolysis products, such as formaldehyde (CH₂O, m/z = 30), acetone (C₃H₆O, m/z = 58), nor-3-caronaldehyde (C₉H₁₄O₂, m/z = 154), nor-3-caralic acid (C₈H₁₂O₃, m/z = 156), 3-caronaldehyde (C₁₀H₁₆O₂, m/z = 168), 3-caralic acid (C₉H₁₄O₃, m/z = 170), and 3-caronic acid (C₁₀H₁₆O₃, m/z = 184). Moreover, the ozonolysis products, C₈H₁₂O₂ (m/z = 140), C₈H₁₄O₂ (m/z = 142), C₁₀H₁₆O (m/z = 152), and C₁₀H₁₄O₃ (m/z = 182) were identified in the experiments for the first time. Based on literature results and comprehensive analysis of the experimental data, we elucidated detailed reaction pathway mechanisms for these newly discovered products.