An in situ study of the thermal decomposition of 2,2'-azobis(2-methylpropionitrile) radical chemistry using a dual-mode EPR resonator
An in situ study of the thermal decomposition of 2,2'-azobis(2-methylpropionitrile) radical chemistry using a dual-mode EPR resonator
复制标题
使用双模式 EPR 谐振器对 2,2-偶氮双（2-甲基丙腈）自由基化学的热分解进行原位研究
DOI：
10.1007/s11164-022-04861-z
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发表时间：
2022
影响因子：
3.3
通讯作者：
Magri G
中科院分区：
文献类型：
--
作者：
Magri G
采用自制的双模EPR谐振器研究了AIBN热分解过程中的自由基化学。该谐振器可以同时使用微波和EPR测量进行原位加热。比较了传统加热方法和微波（或介电）加热方法对AIBN的热分解效果。在两种加热条件下，EPR检测到的自由基包括2-氰基-2-丙基（CP●）和2-氰基-2-丙氧基（CPO●）自由基。在有氧条件下，EPR观察到的这些自由基的相对分布与传统方法或电介质方法缓慢加热后的分布相似。在这两种条件下，在大约80-90°C的温度下，动力学上有利的CPO●自由基及其加合物主导着EPR光谱。在厌氧条件下，随着CPO●的减少，分布可以改变。然而，当应用快速加热（主要使用毫瓦诱导的t跳变）时，观察到的结果显着不同。由于在更快的时间尺度上达到更高的反应温度，因此在EPR光谱中实际上看不到ST●-CPO加合物。因此，与使用传统加热方法进行的实验相比，微波产生的更快速和更容易的加热能力可能导致无法检测到自由基中间体。
A custom-built dual-mode EPR resonator was used to study the radical chemistry of AIBN thermal decomposition. This resonator enables both simultaneous in situ heating using microwaves and EPR measurements to be performed. The thermal decomposition of AIBN was compared following conventional heating methods and microwave-induced (or dielectric) heating methods. Under both heating conditions, the radicals formed and detected by EPR include the 2-cyano-2-propyl (CP●) and 2-cyano-2-propoxyl (CPO●) radicals. Under aerobic conditions, the observed relative distribution of these radicals as observed by EPR is similar following slow heating by conventional or dielectric methods. In both conditions, the kinetically favoured CPO●radicals and their adducts dominate the EPR spectra up to temperatures of approximately 80–90 °C. Under anaerobic conditions, the distribution can be altered as less CPO●is available. However, the observed results are notably different when rapid heating (primarily applied using a MW-induced T-jump) is applied. As the higher reaction temperatures are achieved on a faster timescale, none of the ST●-CPO adducts are actually visible in the EPR spectra. The more rapid and facile heating capabilities created by microwaves may therefore lead to the non-detection of radical intermediates compared to experiments performed using conventional heating methods.