Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate



Ashlee Aiello, John Hoffman, Anthony Kotula, Lucas Flagg, Ruipeng Li, Jeremiah Woodcock


Spontaneous room temperature crystallization of 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) was observed upon removal of trace water. To ensure that this observation was not produced by trace water or other contaminants, sample purity was confirmed using analytical nuclear magnetic resonance spectroscopy. Raman spectroscopy and simultaneous quartz crystal microbalance/infrared spectroscopy measurements were used to study molecular reorganization that occurred during crystallization and decrystallization using trace water in the form of atmospheric moisture. These experimental results were supplemented with density functional theory calculations that indicate imidazolium cation ring stacking and side chain clustering with an exclusive arrangement of the acetate anion in the cation ring plane upon water removal, which is in agreement with other theoretical reports in the literature. Crystal structure formation was confirmed using two-dimensional wide angle X-ray scattering. This natural crystallization is attributed to removal of trace water over extended periods of time and calls attention to the molecular-level role of water in the structure of hydroscopic ionic liquid systems.
Journal of Physical Chemistry B


ionic liquid, [EMIm][OAc], crystallization, water contamination


Aiello, A. , Hoffman, J. , Kotula, A. , Flagg, L. , Li, R. and Woodcock, J. (2023), Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate, Journal of Physical Chemistry B, [online],, (Accessed June 13, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created May 16, 2023, Updated September 27, 2023