In most of the applications, the
stability of ionic liquids, at least at a certain extent, is crucial
for optimum process performance.
It is widely claimed that many of the new ionic liquids
are both air and moisture stable; some are even hydrophobic. While it
is true to say that the new liquids are free from many of the
hydrolysis problems that make the halogenoaluminates(III) so difficult
to handle, most ammonium and imidazolium
salts are hygroscopic and if
used in open vessels, hydration will almost certainly occur.
For example, despite their widespread use, IL featuring PF6- and BF4-
have been reported to sometimes decompose when heated in the presence
of water, giving off HF.
to which this is a problem will depend on the use to which the ionic
liquid is being put and what solutes are being used. For instance, the
small amounts of highly reactive species that are used as catalysts can
be deactivated by even the smallest amounts of water. It would
be recommended handling under an inert atmosphere if the ionic liquids
to be used for air- or moisture-sensitive solutes.
new ionic liquids are much easier to handle than the
halogenoaluminate(III) systems and are opening up new avenues for
research, particularly in homogeneous catalysis. Furthermore, previous
that, although not 100% inert, certain ionic liquids
incorporating 1,3-dialkyl imidazolium
cations are generally
more resistant than traditional solvents under certain harsh
process conditions, such as those occurring in oxidation,
photolysis and radiation processes.
the room-temperature ionic liquids that have received
attention are [EtNH3][NO3], [emim][NO3], and [emim][ClO4]. Organic
nitrates and perchlorates are potentially explosive, especially when
rigorously dried. Although no problems have been reported, care should
be used at all times when handling them.
Nowadays the most widely
used ionic liquids are probably N,N-dialkylimidazolium