@article {2460,
	title = {Hydrophobicity/Hydrophilicity of 1-Butyl-2,3-dimethyl and 1-Ethyl-3-methylimodazolium Ions: Toward Characterization of Room Temperature Ionic Liquids},
	journal = {Journal of Physical Chemistry B},
	volume = {113},
	number = {44},
	year = {2009},
	note = {ISI Document Delivery No.: 510QMTimes Cited: 2Cited Reference Count: 52Kato, Hitoshi Miki, Kumiko Mukai, Tomohiro Nishikawa, Keiko Koga, Yoshikata},
	month = {Nov},
	pages = {14754-14760},
	type = {Article},
	abstract = {We continue to experimentally characterize the constituent ions of room temperature ionic liquids in terms of their interactions with H2O. By using the so-called 1-propanol probing methodology, we experimentally index the relative hydrophobicity/hydrophilicity of a test ion. In this paper, we examine 1-butyl-2,3 dimethylimidazolium (abbreviated as [C(4)C(1)mim](+)) and 1-ethyl-3-methylimidazolium ([C(2)mim](+)). We found that [C(4)C(1)mim](+) dissociates completely in dilute aqueous solution less than 0.006 mol fraction, and hence, its hydrophobicity/hydrophilicity could be determined. The results indicate that [C(4)C(1)mim](+) is highly amphiphilic with much stronger hydrophobicity and hydrophilicity than normal ions. Our earlier similar studies indicated the same conclusion for such typical constituent ions as 1-butyl-3-methylimidazolium ([C(4)mim](+)) PF6-, CF3SO3-, and N(SO2CF3)(2)(-). Hence, we suggest that the constituent ions of room temperature ionic liquids that we have studied so far are all amphiphiles with much stronger hydrophobicity and hydrophilicity than normal ions. We found, furthermore, that the hydrophobicity and hydrophilicity of [C(4)C(1)mim](+) are stronger than those for [C(4)mim](+). A possible reason for higher hydrpohilicity is discussed in terms of strong acidic character of H on the C(2) of the imidazolium ring, which tends to attract the delocalized positive charge toward itself oil forming a hydrogen bond to H2O. On replacing it with CH3 in [C(4)C(1)mim](+), the lack of acidic H enhances the positive charge in the vicinity of N-C-N in the ring that interacts with the surrounding H2O strongly to an induced dipole of O of the H2O. For [C(2)mim](+), we found it does not dissociate completely, even in dilute aqueous solution, and hence, we could not characterize it within the present methodology.},
	keywords = {1-BUTYL-3-METHYLIMIDAZOLIUM BROMIDE, AGGREGATION BEHAVIOR, ALKYL CHAIN-LENGTH, APPROACH, AQUEOUS-SOLUTIONS, HOFMEISTER SERIES, MIXING SCHEMES, MOLECULAR-ORGANIZATION, partial molar enthalpy, PHYSICOCHEMICAL PROPERTIES, THERMODYNAMIC},
	isbn = {1520-6106},
	url = {<Go to ISI>://000271105600027},
	author = {Kato, H. and Miki, K. and Mukai, T. and Nishikawa, K. and Koga,Yoshikata}
}
@article {2302,
	title = {Experimental determination of the third derivative of G. I. Enthalpic interaction},
	journal = {Journal of Chemical Physics},
	volume = {129},
	number = {21},
	year = {2008},
	note = {ISI Document Delivery No.: 379XWTimes Cited: 2Cited Reference Count: 19Westh, Peter Inaba, Akira Koga, Yoshikata},
	month = {Dec},
	pages = {4},
	type = {Article},
	abstract = {The solute (i)-solute interaction in terms of enthalpy, H-i-i(E)=N(partial derivative H-2(E)/partial derivative n(i)(2))=(1-x(i))(partial derivative H-2(E)/partial derivative n(i)partial derivative x(i)), the third derivative of G, was experimentally determined using a Thermal Activity Monitor isothermal titration calorimeter for aqueous solutions of 2-butoxyethanol (BE) and 1-propanol (1P). This was done using both calorimetric reference and sample vessels actively. We simultaneously titrate small and exactly equal amounts of solute i (=BE or 1P) into both cells which contain the binary mixtures at an average mole fraction, x(i), which differs by a small amount Delta x(i). The appropriate amount of titrant delta n(i) was chosen so that the quotient (delta H-E/delta n(i)) can be approximated as (partial derivative H-E/partial derivative n(i)), and so that the scatter of the results is reasonable. delta H-E is the thermal response from an individual cell on titration, and we measure directly the difference in the thermal response between the two cells, Delta(delta H-E). The resulting quotient, Delta(delta H-E)/delta n(i)/Delta x(i), can be approximated as (partial derivative H-2(E)/partial derivative n(i)partial derivative x(i)) and hence provides a direct experimental avenue for the enthalpy interaction function. We varied the value of Delta x(i) to seek its appropriate size. Since H-E contains the first derivative of G with respect to T, the result is the third derivative quantity. Thus we present here a third derivative quantity directly determined experimentally for the first time.},
	keywords = {AQUEOUS-SOLUTIONS, calorimetry, DYNAMICS, enthalpy, fluctuations, H2O, HOFMEISTER SERIES, LIQUID MIXTURES, MOLECULAR-ORGANIZATION, organic compounds, SOLVATION, WATER},
	isbn = {0021-9606},
	url = {<Go to ISI>://000261430900001},
	author = {Westh, P. and Inaba, A. and Koga,Yoshikata}
}
@article {1201,
	title = {Hydrophobicity vs hydrophilicity: Effects of poly(ethylene glycol) and tert-butyl alcohol on H2O as probed by 1-propanol},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {41},
	year = {2005},
	note = {ISI Document Delivery No.: 974SQTimes Cited: 8Cited Reference Count: 33},
	month = {Oct},
	pages = {19536-19541},
	type = {Article},
	abstract = {The enthalpic interaction between 1-propanol (IP) molecules, H-1P- 1P(E), was evaluated in 1P-poly(ethleneglycol) (PEG)-H2O and 1P-tert-butyl alcohol (TBA)-H2O ternary mixtures. The model-free and experimentally accessible quantity, H-1P-1p(E), indicates the effect of an additional 1P on the actual enthalpic situation of 1P in the mixture. It was shown earlier that the composition dependence of H-1P-1P(E) reflects the process how 1P modifies H2O. This H-1P-1P(E) pattern changes in the presence of a third component, PEG or TBA. The effects of PEG or TBA on the molecular organization of H2O were elucidated from these induced changes. Together with previous similar studies for the effects of methanol (ME), 2-propanol (2P), ethylene glycol (EG), and glycerol (Gly), we suggest a method and hence a possible scaling for sorting out hydrophobicity vs hydrophilicity of these alcohols by the changes induced to the loci of the maxima in H-1P-1P(E). We show that hydrophilicity scales with the number of oxygen, regardless of whether O is the ether -O- or the hydroxyl -OH. Hydrophobicity also scales with the number of carbon atoms for alcohols without a methyl group. For those with methyl groups, the hydrophobicity seems proportional to the total number of carbon with a different proportionality factor from those without methyl group.},
	keywords = {25-DEGREES-C, ALKANE-MONO-OLS, AQUEOUS-SOLUTIONS, EXCESS CHEMICAL-POTENTIALS, GLYCEROL, HOFMEISTER SERIES, MIXING SCHEMES, MOLECULAR-ORGANIZATION, PARTIAL MOLAR ENTHALPIES, THERMODYNAMIC APPROACH},
	isbn = {1520-6106},
	url = {<Go to ISI>://000232612100072},
	author = {Miki, K. and Westh, P. and Koga,Yoshikata}
}
