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Updated: Aug 1, 2025

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors
Published on: April 27, 2017
Fine-tuning the Basicity of Deep Eutectic Solvents by Substituting Guanidine for Urea in Reline
Tatsuya Umecky1, Akihiro Goto1, Naoki Hayashi1
1Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga, 840-8502, Japan.
Abstract:
The physicochemical properties of deep eutectic solvents (DESs) depend on the combination of hydrogen bond acceptors and hydrogen bond donors used. The basicity of a DES significantly influences its performance in CO2 chemical absorption, biomass and protein dissolution, and catalytic reactions. To the best of our knowledge, a strategy for fine-tuning the basicity of DESs has not yet been reported. Therefore, in this study, we substituted the base urea (Ur) in reline, which is a 1:2 mixture of choline chloride (ChCl) and Ur, with the superbase guanidine (Gu) to fine-tune its basicity. Binary (2Gu-ChCl) and ternary (Gu-Ur-ChCl) DESs were prepared, and their CO2 absorption capacities were investigated at 313.2 K. The equimolar mixture Gu-Ur-ChCl absorbed CO2 gas up to the molar ratio [CO2]/[ChCl] ≈ 1.0. Therefore, the basicity of ChCl-based DES can be continuously varied by substituting more molecules of Ur with Gu. Our strategy of combining functional and non-functional molecules with similar structures to vary the basicity of DESs has potentially wide applications that utilize DESs in the future.
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