Refractive Index of 48 Neat Deep Eutectic Solvents and of Selected Mixtures: Effect of Temperature, Hydrogen-Bonding Donors, Hydrogen-Bonding Acceptors, Mole Ratio, and Water

Jinkai Luan; Yan Cheng; Fumin Xue; Li Cui; Daijie Wang

doi:10.1021/acsomega.3c03502

Refractive Index of 48 Neat Deep Eutectic Solvents and of Selected Mixtures: Effect of Temperature, Hydrogen-Bonding Donors, Hydrogen-Bonding Acceptors, Mole Ratio, and Water

ACS Omega. 2023 Jun 30;8(28):25582-25591. doi: 10.1021/acsomega.3c03502. eCollection 2023 Jul 18.

Authors

Jinkai Luan^{1

2}, Yan Cheng², Fumin Xue², Li Cui², Daijie Wang¹

Affiliations

¹ School of Chemistry and Chemical Engineering, Heze Branch of Qilu University of Technology (Shandong Academy of Sciences), Heze 274000, China.
² Shandong Analysis and Test Center, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250014, China.

Abstract

The refractive index (RI) is an important physiochemical property of deep eutectic solvents (DESs) for application in the optical identification of specific substances or measuring the concentration of solutes in solutions. However, the available data on the RI of DESs is limited. Here, a systematic investigation on the RI of 48 typical DESs and 30 mixtures with water was conducted under atmospheric pressure. The effect of temperature in the range 293.15-338.15 K, hydrogen-bonding donors (HBDs), and hydrogen-bonding acceptors (HBAs) on RI was investigated. Furthermore, the RI of DESs as a function of mass percentage in the range of 20-80% water was also studied. It was found that the RI of DESs and its aqueous binary mixtures decreases linearly with the increase of temperature. HBDs and HBAs had a significant influence on the RI of DESs. Among them, the RI of choline chloride (ChCl)/phenol and ChCl/o-cresol were obviously higher than those of other DESs. It was also found that the addition of water would decrease the RI of DESs, and the RI of DES content in percentage (wt %) of water binary mixtures increases linearly as a function of mass percentage of DESs for 20 DESs. However, for the other 10 DESs, there is no linear relationship between the RI and the DES content.