Cation Symmetry effect on the Volatility of Ionic Liquids

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Marisa A A Rocha (Author) Other; Joao A P Coutinho (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: Journal of Physical Chemistry B

Vol. 116 No. 6

Pages: 10922-10927

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 70 Citations

Scopus - 72 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-002-5J1

DOI: 10.1021/jp306937f

Abstract (EN): This work reports the first data for the vapor pressures at several temperatures of the ionic liquids, [C(N/2)C(N/2)im][NTf2] (N = 4, 6, 8, 10, 12) measured using a Knudsen effusion apparatus combined with a quartz crystal microbalance. The morphology and the thermodynamic parameters of vaporization derived from the vapor pressures, are compared with those for the 1-alkyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide series, [C(N-1)C(1)im][NTf2] (N = 3 - 9, 11, and 13). It was found that the volatility of [C(N/2)C(N/2)im][NTf2] series is significantly higher than the asymmetric cation ILs with the same total number of carbons in the alkyl side chains, [C(N-1)C(1)im][NTf2]. The observed higher volatility is related with the lower enthalpy of vaporization. The symmetric cation, [C(N/2)C(N/2)im][NTf2], presents lower entropies of vaporization compared with the asymmetric [C(N-1)C(1)im][NTf2], indicating an increase of the absolute liquid entropy in the symmetric cation ILs, being a reflection of a change of the ion dynamics in the IL liquid phase. Moreover both the enthalpy and entropy of vaporization of the [C(N/2)C(N/2)im][NTf2] ILs, present a clear odd-even effect with higher enthalpies/entropies of vaporization for the odd number of carbons in each alkyl chain ([C(3)C(3)im][NTf2] and [C(5)C(5)im][NTf2]).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6