Yu Chang, Liang Min, Dai Su-Yi, Cheng Hai-Jun, Ma Li, Lai Fang, Liu Xiong-Min, Li Wei-Guang
College of Chemistry and Chemical Engineering, Guangxi University Nanning 530004 Guangxi China
RSC Adv. 2021 Oct 5;11(52):32654-32670. doi: 10.1039/d1ra04836h. eCollection 2021 Oct 4.
Cinnamaldehyde, cinnamyl alcohol, β-methylstyrene and cinnamic acid are four important biomass 3-phenyl-2-propene compounds. In the field of perfume and organic synthesis, their thermal stability and oxidation pathways deserve attention. This paper reports a new attempt to investigate the thermal stability and reactivity by a custom-designed mini closed pressure vessel test (MCPVT). The pressure and temperature behaviors were measured by MCPVT under nitrogen and oxygen atmosphere. The temperature of initial oxygen absorption ( ) and rapid oxidation ( ) were calculated. The results showed that four 3-phenyl-2-propene compounds were stable under nitrogen atmosphere. The of cinnamaldehyde, cinnamyl alcohol, β-methylstyrene, and cinnamic acid was 271.25 K, 292.375 K, 323.125 K, and 363.875 K, and their was 301.125 K, 332.75 K, 357.91 K, and 385.375 K, respectively. The oxidation reactivity order was derived to be cinnamaldehyde > cinnamyl alcohol > β-methylstyrene > cinnamic acid. The oxidation kinetics were determined using time (-) plots, which showed a second-order reaction. Peroxide was determined by iodimetry, and the oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the peroxide value of cinnamaldehyde, cinnamyl alcohol, β-methylstyrene, and cinnamic acid reached 18.88, 15.07, 9.62, and 4.24 mmol kg at 373 K for 6 h, respectively. The common oxidation products of four 3-phenyl-2-propene compounds were benzaldehyde, benzoic acid, and epoxide, which resulted from the carbon-carbon double bond oxidation. The substituents' oxidation products were obtained from the oxidation of cinnamaldehyde, cinnamyl alcohol, and β-methylstyrene. In particular, the difference is that no oxidation products of the carboxyl group of cinnamic acid were detected. The common oxidation products of the four 3-phenyl-2-propene compounds were benzaldehyde, benzoic acid, and epoxide, which resulted from the carbon-carbon double bond oxidation. The substituents' oxidation products were caught in the oxidation of cinnamaldehyde, cinnamyl alcohol, and β-methylstyrene. In particular, the difference is that no oxidation products of the carboxyl group of cinnamic acid were detected. According to the complex oxidation products, important insights into the oxidation pathways were provided.
肉桂醛、肉桂醇、β-甲基苯乙烯和肉桂酸是四种重要的生物质3-苯基-2-丙烯化合物。在香料和有机合成领域，它们的热稳定性和氧化途径值得关注。本文报道了一种通过定制设计的微型密闭压力容器试验（MCPVT）来研究热稳定性和反应活性的新尝试。在氮气和氧气气氛下，利用MCPVT测量了压力和温度行为。计算了初始吸氧温度（ ）和快速氧化温度（ ）。结果表明，四种3-苯基-2-丙烯化合物在氮气气氛下是稳定的。肉桂醛、肉桂醇、β-甲基苯乙烯和肉桂酸的初始吸氧温度分别为271.25 K、292.375 K、323.125 K和363.875 K，它们的快速氧化温度分别为301.125 K、332.75 K、357.91 K和385.375 K。得出的氧化反应活性顺序为肉桂醛＞肉桂醇＞β-甲基苯乙烯＞肉桂酸。利用时间（-）曲线确定了氧化动力学，结果表明为二级反应。通过碘量法测定过氧化物，并用气相色谱-质谱联用仪（GC-MS）分析氧化产物。结果表明，在373 K下反应6 h后，肉桂醛、肉桂醇、β-甲基苯乙烯和肉桂酸的过氧化物值分别达到18.88、15.07、9.62和4.24 mmol kg。四种3-苯基-2-丙烯化合物的常见氧化产物为苯甲醛、苯甲酸和环氧化物，它们是由碳-碳双键氧化产生的。取代基的氧化产物是在肉桂醛、肉桂醇和β-甲基苯乙烯的氧化过程中得到的。特别的是，不同之处在于未检测到肉桂酸羧基的氧化产物。四种3-苯基-2-丙烯化合物的常见氧化产物为苯甲醛、苯甲酸和环氧化物，它们是由碳-碳双键氧化产生的。取代基的氧化产物是在肉桂醛、肉桂醇和β-甲基苯乙烯的氧化过程中捕获到的。特别的是，不同之处在于未检测到肉桂酸羧基的氧化产物。根据复杂的氧化产物，对氧化途径提供了重要的见解。
