Dermatochemistry and Skin Allergy, Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
Chem Res Toxicol. 2011 Sep 19;24(9):1507-15. doi: 10.1021/tx200120q. Epub 2011 Aug 26.
The autoxidation of geranial with O(2) was studied both experimentally and using density functional theory. Computational results were used to interpret experimentally observed product ratios. Geranial was found to autoxidize, forming 6,7-epoxygeranial as the main oxidation product. Hydroperoxides corresponding to those identified as important skin sensitizers in previous studies of fragrance terpenes could not be detected. Instead, a dioxolan derivative and its corresponding hydroperoxide were identified and detected in high concentrations. The distribution of products in autoxidation generally depends on the stabilities of the intermediate peroxyl radicals. In this study, the formation of a peracyl radical was found to be highly favored. This radical forms peracid which epoxidizes geranial. The epoxide thus produced can react with acyl radical to yield the dioxolan hydroperoxide. The dioxolan derivative is believed to form in an acid catalyzed closed shell reaction between 6,7-epoxygeranial and geranial. The dioxolan hydroperoxide and 6,7-epoxygeranial are strong sensitizers and are considered to be the compounds mainly responsible for the skin sensitization potency of air-exposed geranial.
香叶醛与 O(2) 的自动氧化作用既通过实验又通过密度泛函理论进行了研究。使用计算结果对实验观察到的产物比例进行了解释。研究发现香叶醛自动氧化，形成 6,7-环氧香叶醛作为主要氧化产物。先前研究香料萜烯中作为重要皮肤致敏物的过氧化物未能检测到。相反，检测到了高浓度的二氧戊环衍生物及其相应的过氧化物。自动氧化中产物的分布通常取决于中间过氧自由基的稳定性。在这项研究中，发现过酰基自由基的形成非常有利。该自由基形成过酸，过酸使香叶醛环氧化。因此产生的环氧化物可以与酰基自由基反应生成二氧戊环过氧化物。据信，二氧戊环衍生物是在 6,7-环氧香叶醛和香叶醛之间的酸催化封闭壳反应中形成的。二氧戊环过氧化物和 6,7-环氧香叶醛是强敏化剂，被认为是空气中暴露的香叶醛的皮肤致敏能力的主要化合物。
