The co-pyrolysis of the coal-like model compounds cinnamic acid and its derivatives with NHCl or NHCl was investigated at medium temperatures (500 °C, 600 °C, 700 °C). The resulting products were examined by GC-MS to analyze the pyrolysis process, and the validation was assisted by using nuclear magnetic resonance (NMR) detection and computational simulation, and the mechanism of product formation. Relatively high yields of pyrolysis products were observed at 600 °C. The special structure of cinnamic acid, especially the triple conjugated moiety with a benzene ring, double bond and carboxyl group is amenable to electron transfer during its pyrolysis with NHCl, which leads to cinnamonitrile or quinoline derivatives. However, the free radical reaction is extremely rapid, and the existing detection methods are limited to the analysis of the 1equilibrium reaction results at a certain time point. By adding NHCl for isotopic tracing, the N-substituted product after isotopic exchange was successfully captured. It was found that when there is no substituent group on the benzene ring, the reaction products were both quinoline and cinnamonitrile, and cinnamonitrile was slightly more than quinoline. For methyl, the pyrolysis of both 2-methylcinnamic acid and 3-methylcinnamic acid resulted in the corresponding methylcinnamonitrile as the main product due to the combined control of the reaction by the electronic and site-resistant effects of methyl, but 8-methylquinoline was also detected among the pyrolysis products of 3-methylcinnamic acid with NHCl, whereas the pyrolysis of 4-methylcinnamic acid yielded 7-methylquinoline as the main product. This experiment reveals the evolution of the products of cinnamic acid and its derivatives during pyrolysis with NHCl. At the same time, it offers a method for the preparation of substituted cinnamonitriles and quinolines using pyrolysis, while also validating the reaction mechanism using isotopic labeling.

中文翻译：

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使用 15N 同位素标记揭示热解过程中甲基肉桂酸转化为含氮化合物

研究了类煤模型化合物肉桂酸及其衍生物与 NHCl 或 NHCl 在中温（500 °C、600 °C、700 °C）下的共热解。通过GC-MS检测所得产物以分析热解过程，并通过核磁共振（NMR）检测和计算模拟以及产物形成机制辅助验证。在 600 °C 时观察到热解产物产率相对较高。肉桂酸的特殊结构，特别是具有苯环、双键和羧基的三重共轭部分，在与NH4Cl热解过程中易于发生电子转移，从而产生肉桂腈或喹啉衍生物。然而自由基反应极其迅速，现有的检测方法仅限于分析某一时间点的1平衡反应结果。通过添加NH4Cl进行同位素示踪，成功捕获了同位素交换后的N-取代产物。发现当苯环上没有取代基时，反应产物均为喹啉和肉桂腈，且肉桂腈略多于喹啉。对于甲基来说，由于甲基的电子效应和位点抗性效应共同控制反应，2-甲基肉桂酸和3-甲基肉桂酸的热解均产生相应的甲基肉桂腈作为主要产物，但8-甲基喹啉也被分解。在 3-甲基肉桂酸与 NH4Cl 的热解产物中检测到，而 4-甲基肉桂酸的热解产生 7-甲基喹啉作为主要产物。该实验揭示了肉桂酸及其衍生物在 NH4Cl 热解过程中产物的演变。同时，它提供了一种利用热解制备取代肉桂腈和喹啉的方法，同时还利用同位素标记验证了反应机理。