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Innovative Approach: Green Synthesis of Polyethyleneimines using Ethylene Glycol and Ethylenediamine

Innovative Approach: Green Synthesis of Polyethyleneimines using Ethylene Glycol and Ethylenediamine

Polyethyleneimines (PEIs) are widely used in various applications such as detergents, adhesives, cosmetics, gene therapy, and CO2 capture. The conventional method of producing branched PEIs involves the use of toxic and mutagenic chemicals, raising concerns for human health and the environment.

However, a new method has been reported for synthesizing branched PEIs using safer and commercially available feedstock, namely ethylene glycol and ethylenediamine. The reaction is catalyzed by a manganese complex and only produces water as a by-product. Mechanistic studies indicate that the reaction proceeds through the formation and hydrogenation of imine intermediates.

Facts:

  • 👥 Polyethyleneimines (PEIs) are widely used in products like detergents, adhesives, cosmetics, and for processes such as gene therapy and CO2 capture.
  • ❌ The conventional method of producing branched PEIs uses toxic and mutagenic aziridine feedstock, which poses risks to human health and the environment.
  • 🌱 A novel method has been developed to synthesize branched PEIs using safer and commercially available feedstock, ethylene glycol and ethylenediamine.
  • ⚛️ The synthesis reaction is catalyzed by a complex of the earth-abundant metal, manganese.
  • 🌊 The reaction liberates water as the only by-product.
  • 🔬 Mechanistic studies involving both computational simulations and experiments suggest that the reaction proceeds through the formation and subsequent hydrogenation of imine intermediates.

Polyethyleneimines (PEIs) have diverse applications ranging from everyday products like detergents and adhesives to advanced processes such as gene therapy and CO2 capture. However, the current method of producing branched PEIs involves the use of aziridine feedstock, which is highly toxic, volatile, and mutagenic. This poses significant risks to human health and the environment. In this publication, the authors present a novel method for synthesizing branched PEIs using ethylene glycol and ethylenediamine as feedstock, which are safer, commercially available, and potentially renewable.

The key advancement lies in the catalytic system used, where a complex of the abundant metal manganese is employed. This catalytic system facilitates the polymerization reaction, resulting in the formation of branched PEIs. Notably, the reaction solely produces water as a by-product, making it environmentally benign. To gain insights into the reaction mechanism, the authors conducted mechanistic studies using a combination of density functional theory (DFT) computations and experimental techniques. These studies revealed that the reaction proceeds through the formation and subsequent hydrogenation of imine intermediates.

Overall, this research presents an innovative approach to synthesizing branched PEIs, offering a safer and more sustainable alternative to the conventional method. By using readily available feedstock and an earth-abundant metal catalyst, this method has the potential for broader implementation in industrial settings, contributing to the reduction of toxic chemicals and environmental impact.

Angewandte International Edition Chemie Title: Synthesis of Polyethyleneimines from the Manganese Catalyzed Coupling of Ethylene Glycol and Ethylenediamine 

Brodie; Owen; Kolb; Bühl; Kumar; Brodie; Owen; Kolb; Bühl; Kumar; Brodie; Owen; Kolb; Bühl; Kumar

Full-text link: https://doi.org/10.1002/anie.202306655

What this paper is about

  • The synthesis of imines has been reported from the dehydrogenative coupling of alcohols and amines.
  • Here, we report a direct synthesis of branched polyethyleneimine from the manganese-catalyzed coupling of ethylene glycol and ethylene diamine.
  • Using 2 mol% of complex 1 and 10 mol% of K2CO3 for 24 h at 170 C resulted in a mixture of u-PEI-1 and PEI-1 with moderate yield 10.1002/anie.202306655.

What you can learn

  • The methodology is significantly greener than the current state of the art as it substitutes a highly toxic feedstock, aziridine with much safer and potentially renewable feedstock.
  • The characterization studies of the polymer showed that the formed polymer is a branched polyethyleneimine with high molecular weights.
  • Based on the DFT computation, experimental and prior studies, we suggest a hydrogen borrowing pathway where the reaction proceeds via the dehydrogenative condensation of ethylene glycol with ethylene diamine to form imine intermediates followed by their subsequent hydrogenation to form polyethyleneimine as depicted in Scheme 2.

FAQ

Q: What are Polyethyleneimines (PEIs)?

A: Polyethyleneimines (PEIs) are a type of polymer with diverse applications in products like detergents, adhesives, cosmetics, gene therapy, and CO2 capture.

Q: What does PEIs stand for?

A: PEIs stands for Polyethyleneimines.

Q: What are branched PEIs?

A: Branched PEIs refer to a specific form of Polyethyleneimines that have a branched structure. They are commonly used in various industries.

Q: What is ethylene glycol?

A: Ethylene glycol is a commercially available feedstock used in the synthesis of Polyethyleneimines. It is a colorless liquid commonly used as an antifreeze and in the production of polyester fibers.

Q: What is ethylenediamine?

A: Ethylenediamine is another commercially available feedstock used in the synthesis of Polyethyleneimines. It is a colorless liquid with a strong ammonia-like odor and is commonly used in various chemical processes.

Q: What is manganese catalysis?

A: Manganese catalysis refers to the use of a complex of the earth-abundant metal manganese as a catalyst in a chemical reaction. In this case, it is used to facilitate the synthesis of Polyethyleneimines from ethylene glycol and ethylenediamine.

Q: What are imine intermediates?

A: Imine intermediates are chemical compounds that form during the reaction process of synthesizing Polyethyleneimines. They play a crucial role in the reaction mechanism and are subsequently hydrogenated to form the final product.

Q: What is meant by safer synthesis?

A: Safer synthesis refers to a method or process that reduces or eliminates the use of toxic or hazardous substances, minimizing risks to human health and the environment. In this context, the novel method of synthesizing Polyethyleneimines using ethylene glycol and ethylenediamine is considered safer compared to the conventional method that uses toxic and mutagenic chemicals.

Q: What does environmentally benign mean?

A: Environmentally benign refers to a process or product that has minimal or no harmful impact on the environment. In the context of the synthesis of Polyethyleneimines, the reaction using ethylene glycol, ethylenediamine, and manganese catalyst produces water as the only by-product, making it environmentally benign compared to conventional methods that generate toxic waste.

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