Mechanism of Formation of Volatile Organic Compounds from Oxidation of Linseed Oil

Abstract

The pathways of volatile organic compound (VOC) formation have been investigated through a computational study, employing the Gaussian 03 suite of programs. We optimized geometries and zero-point vibrational energies (ZPVEs) at the B3LYP/6-31G­(d) level of theory and improved electronic energies by conducting single-point energy calculations using the large 6-311++G­(3df,3pd) basis set. To describe the predominant mechanism of the linseed oil oxidation, the following sequence is proposed: hydrogen abstraction of unsaturated fatty compounds as the initiation reaction followed by the reaction of allylic-type radicals with molecular oxygen to form peroxyl radicals and finally intramolecular rearrangement through four- and five-membered rings. Quantum calculations identified low-energy pathways following cyclization resulting in the formation of major products observed, especially aldehydes and ketones. The overall energy changes taking place through the four- and five-membered rings were found to be 78 and 93 kJ mol–1 exothermic, respectively. Metal catalysts decompose hydroperoxides based on the Fenton-like mechanism into alkoxyl and peroxyl radicals.

Low temperature oxidation of linseed oil: a review

“…Quantum chemical calculations identified low energy pathways for the decomposition of cyclic peroxides into aldehydes and ketonic species (Juita et al 2011e). …”

Examination of Mechanisms for Formation of Volatile Aldehydes from Oxidation of Oil-Based Systems

“…However, rates are a function of both the rate constant and the concentration of the reactant(s), and given the facile formation of peroxy radicals, they were attractive candidates to lead to the formation of aldehydes. Formation of many small molecules directly from a peroxy radical was proposed by Juita et al Although other volatiles may be formed via lower energy pathways through more stable ring structures, the proposed pathway of interest to form hexanal proceeds through a strained four-membered ring. Given that the researchers were unable to isolate a stable transition state for the decomposition of the dioxetane intermediate, we sought to confirm the lowest energy pathway for this mechanism with G4 since it has recently been demonstrated to have a high level of chemical accuracy for oxygenated and radical species .…”

“…These mechanisms all include cyclization steps before decomposition into small molecules. In work by Juita et al, an allyl peroxy radical species, an early species formed by oxygen addition to a conjugated radical, was examined as a major producer of volatiles . Their computational study followed two pathways for the production of small volatile molecules via either a four-membered dioxetane intermediate or a five-membered ring that could decompose in two elementary steps.…”

Water up-take in fuel pellets studied by Dynamic Vapour Sorption (DVS) analysis and its potential role in self-heating during storage

“…In addition, the increase in temperature caused by condensation will also increase the reaction rate of the exothermal autoxidation of unsaturated fatty acids (Litwinienko 2001;Juita et al 2012). The correlation between the autoxidation process and the produced gases during off-gassing from fuelpellets mentioned above have recently been confirmed (Attard et al 2016;Arshadi et al 2009).…”