Ionic protic impurity

Eor ionic liquids that do not mix completely with water (and which display sufficient hydrolysis stability), there is an easy test for acidic impurities. The ionic liquid is added to water and a pEf test of the aqueous phase is carried out. If the aqueous phase is acidic, the ionic liquid should be washed with water to the point where the washing water becomes neutral. Eor ionic liquids that mix completely with water we recommend a standardized, highly proton-sensitive test reaction to check for protic impurities. 

Obviously, the check for protic impurities becomes crucial if the ionic liquid is to be used for applications in which protons are known to be active compounds. Eor some organic reactions, one has to be sure that an ionic liquid effect does not turn out to be a protic impurity effect at some later stage of the research ... 

Apart from halide and protic impurities, ionic liquids can also be contaminated with other ionic impurities from the metathesis reaction. This is especially likely if the alkali salt used in the metathesis reaction shows significant solubility in the... 

Water in an ionic liquid may be a problem for some applications, but not for others. However, one should in all cases know the approximate amount of water present in the ionic liquid used. Moreover, one should be aware of the fact that water in the ionic liquid may not be inert and, furthermore, that the presence of water can have significant influence on the physicochemical properties of the ionic liquid, on its stability (some wet ionic liquids may undergo hydrolysis with formation of protic impurities), and on the reactivity of catalysts dissolved in the ionic liquid. 

Protic impurities have to be taken into account for two groups of ionic Hquids those that have been produced by an exchange reaction involving a strong acid (often the case, for example, for [BMIM][PF ]), and those that are sensitive to hydrolysis. In the latter case, the protons may originate from the hydrolysis of the anion, forming an acid that may be dissolved in the ionic liquid. 

A closed-loop comprehensive mode] uniting impurity-induced and purposely-added initiator-induced isobutylene (IB) and styrene (St) polymerizations was developed. Both impurity-induced and purposely-induced olefin polymerizations can be both convention or living, and the reaction conditions will determine whether the prevailing mechanism will be conventional or living. The model was used to elucidate the detailed mechanism of olefin polymerizations and to provide guidance toward preparative advances. The heart of the model is the Winstein ionicity spectrum which in its simplest form consists of three fundamental entities connected by two equilibria a) a dormant species (in fact the initiator) which can be either a protic impurity or a purposdully added... 

Apart from halide and protic impurities, ionic liquids can also be contaminated with other ionic impurities from the metathesis reaction. This is especially likely if the alkali salt that is used in the metathesis reaction shows significant solubility in the ionic liquid formed. In this case the ionic liquid can contain significant amounts of the alkali salt. While this may not be a problem even for some catalytic applications (since the presence of the alkali cation may not effect the catalytic cycle of a transition metal catalyst) it is of great relevance for the physicochemical properties of the ionic liquid. 

The addition of thiols to C—C multiple bonds may proceed via an electrophilic pathway involving ionic processes or a free radical chain pathway. The main emphasis in the literature has been on the free radical pathway, and little work exists on electrophilic processes.534-537 The normal mode of addition of the relatively weakly acidic thiols is by the electrophilic pathway in accordance with Markovnikov s rule (equation 299). However, it is established that even the smallest traces of peroxide impurities, oxygen or the presence of light will initiate the free radical mode of addition leading to anti-Markovnikov products. Fortunately, the electrophilic addition of thiols is catalyzed by protic acids, such as sulfuric acid538 and p-toluenesulfonic acid,539 and Lewis acids, such as aluminum chloride,540 boron trifluoride,536 titanium tetrachloride,540 tin(IV) chloride,536 540 zinc chloride536 and sulfur dioxide.541... 

In accordance with the recent lUPAC recommendation the term radical polymerization (RP) will be used in this text instead of free radical polymerization (and analogously only radical instead of free radical). Polymers produced by RP represent roughly 40-45% of all industrial polymers. The dominant position of RP in industry originates from several unique characteristics, which differentiate it from other polymerization methods. Thus, in contrast to ionic or coordination polymerization, RP is tolerant to protic solvents and trace impurities like oxygen, CO2, or monomer stabilizers. 

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