ABSTRACT

Ionic liquids (ILs) with branched and cyclic substituents are seldom studied in the literature, and as such there are little to no data characterizing their thermophysical properties. ILs with branched and cyclic substituents are just as convenient to synthesize and study as their counterparts with linear substituents, but the effects of these substituents on IL properties are not yet well-defined due to the preference for linear substituents. Standard molar vaporization enthalpies of six imidazolium based ionic liquids [Rmim][NTf2] with iso-alkyl and cyclic substituents (R = iso-propyl, iso-butyl, sec-butyl, methylcyclopropyl, cyclopentyl and methylcyclohexyl) were derived from quartz-crystal microbalance (QCM) method. Enthalpies of vaporization measured at elevated temperatures have been adjusted to the reference temperature 298 K and tested for consistency by comparison with the homomorphy alkane, alkylbenzenes and alkyl-imidazoles. It was found that vaporization enthalpies of ILs with the iso-alkyl and cyclic groups are generally on the same level within (+-2 to 3) kJ mol 1 significantly compared to the analogous ILs with the imidazolium cation substituted with the linear alkyl substituents of the same chain length. These findings are useful for the quick estimation of vaporization enthalpies of various substituted IL cations (e.g. pyrrolidinium, ammonium, pyridinium, etc.).

Compounds

#	Formula	Name
1	C9H13F6N3O4S2	1-methyl-3-(1-methylethyl)imidazolium bis[(trifluoromethyl)sulfonyl]imide
2	C10H15F6N3O4S2	1-isobutyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide
3	C10H13F6N3O4S2	1-(cyclopropylmethyl)-3-methyl-1H-imidazolium bis((trifluoromethyl)sulfonyl)amide
4	C10H15F6N3O4S2	1-methyl-3-(1-methylpropyl)imidazolium bis(trifluoromethylsulfonyl)imide
5	C11H15F6N3O4S2	1-cyclopentyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
6	C13H19F6N3O4S2	1-(cyclohexylmethyl)-3-methyl-1H-imidazol-3-ium bis((trifluoromethyl)sulfonyl)amide

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Phase	Method	#Points
POMD	1	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1
POMD	2	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1
POMD	3	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1
POMD	4	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1
POMD	5	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1
POMD	6	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid	Liquid Gas	Derived by Second law	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Structure-property relationships in ionic liquids: Influence of branched and cyclic groups on vaporization enthalpies of imidazolium-based ILs

Zaitsau, D. H.[Dzmitry H.], Varfolomeev, M. A.[Mikhail A.], Verevkin, S. P.[Sergey P.], Stanton, A. D.[Alexander D.], Hindman, M. S.[Michelle S.], Bara, J. E.[Jason E.]

ABSTRACT