Abstract The thermal decomposition of three essential oils has been studied at 300 °C, using a 9% oxygen in nitrogen atmosphere, to mimic the thermal environment of flavours under low-temperature tobacco heating conditions. The starting compositions of the lime, bergamot and cardamom oils were determined by gas chromatography/mass spectrometry (GC/MS). The thermo-oxidative decomposition was evaluated by applying on-line pyrolysis-GC/MS. The main constituents of the oils studied were cyclic and linear monoterpenoids; however, the relative intensities of these components were characteristically different between oils. Lime oil was dominated by monoterpene hydrocarbons, while the other citrus oil, bergamot oil contained in addition a significant number of esters and alcohols. Oxygen-containing monoterpenoids were the dominant constituents of cardamom oil. The relative proportion of the constituents of all three essential oil samples significantly altered during oxidative pyrolysis at 300 °C. The strained rings of bicyclic monoterpenes (pinenes, sabinene, and thujene) underwent scission, resulting in the formation of monocyclic monoterpenes (limonene etc.). Both linear and cyclic terpene acetates decomposed via elimination of acetic acid, so linalyl acetate produced myrcene and ocimene, while terpinyl acetate formed mostly limonene and terpinolene. The relative intensities of linalool and eucalyptol were reduced during pyrolysis, which can be explained by dehydration reactions resulting in the formation of myrcene and ocimene, or limonene and terpinolene, respectively. The chemical reactions that occurred were explained by bond splitting and intramolecular rearrangement mechanisms, with oxygen playing a role in the initiation processes.

中文翻译：

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石灰、佛手柑和豆蔻精油的热氧化分解

摘要 研究了三种精油在 300 °C 下的热分解，在氮气气氛中使用 9% 的氧气，以模拟低温烟草加热条件下香料的热环境。石灰、佛手柑和豆蔻油的起始成分通过气相色谱/质谱法 (GC/MS) 确定。通过应用在线热解-GC/MS 评估热氧化分解。研究的油的主要成分是环状和线性单萜；然而，这些成分的相对强度在不同的油之间存在特征性差异。石灰油以单萜烃为主，而另一种柑橘油佛手柑油还含有大量的酯类和醇类。含氧单萜是豆蔻油的主要成分。在 300 °C 的氧化热解过程中，所有三种精油样品的成分的相对比例都发生了显着变化。双环单萜（蒎烯、蒎烯和 thujene）的张力环发生断裂，导致形成单环单萜（柠檬烯等）。直链和环状萜乙酸酯均通过消除乙酸而分解，因此乙酸芳樟酯产生月桂烯和罗勒烯，而乙酸萜品酯主要形成柠檬烯和萜品油烯。热解过程中芳樟醇和桉油精的相对强度降低，这可以通过脱水反应导致分别形成月桂烯和罗勒烯，或苎烯和萜品油烯来解释。