Kinetics and mechanism for OH-initiated gas-phase chemistry of α-terpineol

Abstract

α-terpineol, mainly released from widely used cleaning products, is an important indoor air pollutant. In this paper, the OH-initiated degradation mechanism of α-terpineol was studied by employing Density Functional Theory (DFT) method. A reaction scheme is proposed for the initial steps. Two barrierless addition processes and the H7-abstraction from the ring are found to be the main reaction pathways. The products, such as 6-hydroxy-hept-5-en-2-one, 4-oxopentanal, acetone, and 4-methyl-3-cyclohexen-1-one, have been detected experimentally, which are confirmed by this theoretical investigation. The suggested formation mechanism of 4-methyl-3-cyclohexen-1-one in the experimental study is not energetically feasible; instead, here an energetically favorable pathway is reported for the first time. The overall rate constant of the title reaction is evaluated to be 1.29 × 10⁻¹⁰ cm³ per molecule per s. The gas-phase residential time of α-terpineol with respect to OH is about 3.1 hours.