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Ionic liquids are green solvents with interesting properties:displaying low melting points and high boiling points.They offer a new approach applicable in many instances.Nevertheless,the presence of free ions can be a matter in some cases,e.g.for the study of nucleophilic reactions,in electrochemistry,and in each situation where there is a competition between counter ions,as in micellization of ionic surfactants.Neutral compounds having formal unit electrical charges of opposite sign,and the same physical properties than ionic liquids would be a nice alternative to these latter solvents.There are two classes of chemical compounds having these characteristics:zwitterionic liquids(with no uncharged canonical representation) and mesoionic liquids(in which the negative and the positive charges are delocalized).In that last class we have chosen to work with 3-methylsydnone in order to examine,in this aprotic solvent,if it was possible to observe aggregation of surfactants in the same manner as in water.With all kinds of surfactants studied(ionic,zwitterionic and mesoionic) we have been able to demonstrate the formation of direct micelles:hydrogen bonding is thus not mandatory for molecular aggregation.Comparison of the behavior in water and in formamide showed that solvophobic interactions were qualitatively comparable but with a lower intensity.
Ionic liquids are green solvents with interesting properties: displaying low melting points and high boiling points. They offer a new approach applicable in many instances. Yet, the presence of free ions can be a matter in some cases, eg for the study of nucleophilic reactions , in electrochemistry, and in each situation where there is a competition between counter ions, as in micellization of ionic surfactants. Neutral compounds having formal unit electrical charges of opposite sign, and the same physical properties than ionic liquids would be a nice alternative to these latter solvents. There are two classes of chemical compounds having these characteristics: zwitterionic liquids (with no uncharged canonical representation) and mesoionic liquids (in which the negative and the positive charges are delocalized) .In that last class we have chosen to work with 3 -methylsydnone in order to examine, in this aprotic solvent, if it was possible to observe aggregation of surfactants in the same manner as in water. All kinds of surfactants studied (ionic, zwitterionic and mesoionic) we have been able to demonstrate the formation of direct micelles: hydrogen bonding is therefore not mandatory for molecular aggregation. Comparison of the behavior in water and in formamide showed that solvophobic interactions were qualitatively comparable but with a lower intensity.