环氧化物与醇和叔胺的开环机理,Polymer Chemistry

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环氧化物与醇和叔胺的开环机理
Polymer Chemistry ( IF 4.1 ) Pub Date : 2023-07-04 , DOI: 10.1039/d3py00481c
Yongzhuang Du ₁ , Xiaoqiang Xue _{1,

2} , Qimin Jiang _{1,

3} , Wenyan Huang _{1,

3} , Hongjun Yang _{1,

3} , Li Jiang _{1,

3} , Bibiao Jiang _{1,

3} , Sridhar Komarneni ₄

Affiliation

本工作研究了叔胺存在下环氧化物的开环机理。使用气相色谱（GC）和尺寸排阻色谱（SEC）来测量聚合物的单体转化率和分子量。核磁共振（NMR）光谱用于分析聚合物结构。研究发现，只有在叔胺和含羟基化合物共存的体系中，才能发生开环反应，表明叔胺和羟基之间存在相互作用，这一点通过混合物的NMR分析得到证实。三乙胺（TEA）和乙醇（EtOH）的聚合，以及TEA和缩水甘油（GL）的聚合。对于普通环氧化物，例如环氧丙烷，在透析前后含有叔胺部分的聚合物，这表明叔胺部分与聚合物主链共价连接，但不作为抗衡离子存在，这是第一个核磁共振证据证实叔胺引发环氧化物的开环反应。与此形成鲜明对比的是，在大量过量的 EtOH 和 TEA 下进行的反应是在 [GL] 下进行的。₀ /[EtOH]₀ /[TEA]₀ = 1/50/50，得到只有一个GL单元的模型化合物。该模型化合物的 NMR 分析证实来自乙醇而不是 TEA 的烷氧基阴离子会攻击并打开 GL 的环氧环。透析前后GL/叔胺聚合物中叔胺部分的存在和不存在进一步支持了烷氧基阴离子引发聚合反应的反应机制，带正电的叔胺单元仅作为抗衡离子存在并被去除通过透析。这些表明叔胺催化环氧化物的开环机制根据其结构而彼此不同。

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Ring-opening mechanism of epoxides with alcohol and tertiary amines

The ring-opening mechanism of epoxides in the presence of tertiary amines was studied in this work. Gas chromatography (GC) and size-exclusion chromatography (SEC) were used to measure the monomer conversion and molecular weights of the polymers. Nuclear magnetic resonance (NMR) spectroscopy was used to analyze the polymer structures. It has been found that only in the system where tertiary amines and hydroxyl-containing compounds coexist can the ring-opening reaction occur, indicating that there is an interaction between tertiary amines and the hydroxyl groups, which is confirmed by the NMR analysis of a mixture of triethylamine (TEA) and ethanol (EtOH), and the polymerization of TEA and glycidol (GL). As for normal epoxides, such as propylene oxide, polymers contained tertiary amine moieties before and after dialysis, suggesting that the tertiary amine moieties were covalently linked with the polymer backbone but were not present as the counter ions, and this is the first NMR proof confirming that tertiary amine initiates the ring-opening reaction of epoxides. In sharp contrast, a reaction at huge excesses of EtOH and TEA was carried out at [GL]₀/[EtOH]₀/[TEA]₀ = 1/50/50, and a model compound with only one GL unit was obtained. The NMR analysis of this model compound confirms that the alkoxy anion from ethanol rather than TEA attacks and opens the epoxy ring of GL. The presence and absence of the tertiary amine moiety in the polymers from GL/tertiary amine before and after dialysis further support the reaction mechanism that an alkoxy anion initiates the polymerization, and the positively charged tertiary amine units are present only as counter ions and are removed by dialysis. These demonstrate that the ring-opening mechanisms catalyzed by tertiary amine for epoxides will be different from each other depending on their structures.

更新日期：2023-07-04

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