J Phys Chem A. 2016 Aug 04;120(30):6059-63. doi: 10.1021/acs.jpca.6b02990. Epub 2016 Jul 21.
Ab Initio Investigation of Cation Proton Affinity and Proton Transfer Energy for Energetic Ionic Liquids.
The journal of physical chemistry. A
Caleb M Carlin, Mark S Gordon
Affiliations
Affiliations
- Department of Chemistry and Ames Laboratory, Iowa State University , Ames, Iowa 50011, United States.
PMID: 27397644
DOI: 10.1021/acs.jpca.6b02990
Abstract
Protonation of the anion in an ionic liquid plays a key role in the hypergolic reaction between ionic liquids and oxidizers such as white fuming nitric acid. To investigate the influence of the cation on the protonation reaction, the deprotonation energy of a set of cations has been calculated at the MP2 level of theory. Specifically, guanidinium, dimethyltriazanium, triethylamine, N-ethyl-N-methyl-pyrrolidinium, N-ethyl-pyridinium, 1,4-dimethyl-1,2,4-triazolium, 1-ethyl-4-methyl-1,2,4-triazolium, and 1-butyl-4-methyl-1,2,4-triazolium were studied. In addition, the net proton transfer energies from the cations to a set of previously studied anions was calculated, demonstrating an inverse correlation between the net proton transfer energy and the likelihood that the cation/anion combination will react hypergolically with white fuming nitric acid. It is suggested that this correlation occurs due to a balance between the energy released by the proton transfer and the rate of proton transfer as determined by the ionicity of the ionic liquid.
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