Thermal Stability of Abietic Acid and Its Oxidation Products

Abstract

The thermal oxidation characteristics of abietic acid were investigated through tracing the oxidation process in custom-designed mini closed pressure vessel test under isothermal and step temperature conditions. Peroxide generation and the peroxide value of abietic acid oxidation process were measured using thin-layer chromatographic analysis and iodimetry. The primary oxidation productperoxidewas separated by column chromatography with further structure characterization, and its thermal decomposition characteristics were assessed via a differential scanning calorimeter (DSC). The oxidation was mainly initiated through the radical generation from hydrogen abstraction on the unsaturated conjugated double bonds of abietic acid above 343 K. The main hydroperoxide, 7-hydroperoxy-13-abiet-8(14)-enoic acid, was found in abietic acid with a high peroxide value. The exothermic onset temperature (T 0) and decomposition heat (Q DSC) of this peroxide were 353.94 K and 545.37 J·g–1, respectively. Finally, a second-stage oxidation process of abietic acid was first investigated when the temperature reached the abietic acid melt point (448 K) with complex oxidation products forming, such as dehydroabietic acid, palustric acid, 7-oxodehydroabietic acid, neoabietic acid, 7-methoxy-tetradehydroabietic acid, 12-deoxyroyleanone acid, and 12-methoxy-abietic acid.

Thermal stability and pathways for the oxidation of four 3-phenyl-2-propene compounds

“…In particular, oxygen consumption rapidly increased near the rapid oxidation temperature. This phenomenon was also observed in the oxidation process of ethers 28 and abietic acid, 29 which was explained by the mechanism of free radical chain reaction. A large number of free radicals were generated by the thermal decomposition of peroxide, accelerating the oxidation to produce complex secondary oxidation products.…”

“…The epoxide compounds might be detected as the further products of peroxides. 29 The plausible mechanism involves the transformation of cinnamaldehyde to an open peroxide, 42 which could be cyclized into a cyclic compound. Furthermore, the epoxidation was ascribed to the addition of peroxyl radicals to the double bonds, followed by unimolecular ring-closure.…”

Influence of gamma irradiation on rosin properties and its antimicrobial activity

“…Moreover, it can be noted that the R-0 has two major stages of thermal degradation, of the first stage is 320 °C and the second stage is 410 °C. The first stage is caused by the cleavage of O−O bond in 7-hydroperoxy-13-abiet-8(14)-enoic acid, and the second stage may be due to the thermal degradation of its three-ring phenanthrene skeleton 43 . From Table 1 it can be noticed that at 120–320 °C the weight loss (%) of R-40 represents the lowest value among samples, while at 410 °C represents the highest value of weight loss (%) among samples.…”

Mechanochemical Synthesis of Rosin-Modified Montmorillonite: A Breakthrough Approach to the Next Generation of OMMT/Rubber Nanocomposites

“…The main stage at the temperature range of 215–276 °C, accompanied by a peak at 256 °C in the corresponding DTG curve, is attributed to the degradation of the abietic acid structure [ 37 , 54 , 55 , 56 ]. The second weight loss at 418–495 °C, in line with the peaks in the DTG curve at 440 °C and 485 °C, is probably associated with degradation of abietic acid residues and their oxidation products [ 57 ].…”