Novel Chloroimidazolium‐Based Ionic Liquids: Synthesis, Characterisation and Behaviour as Solvents to Control Reaction Outcome

Abstract

Novel ionic liquids containing chlorine atoms on the imidazolium cation were synthesised. The physicochemical properties of these ionic liquids were investigated extensively, including glass transition, melting and decomposition temperatures, density, viscosity, miscibility with common solvents and electrochemical window. The behaviour of these ionic liquids as solvents was examined through temperature‐dependent kinetic analyses on two reactions: a nucleophilic aromatic substitution (SNAr) reaction and a bimolecular nucleophilic substitution (SN2) reaction. The properties and effects on reaction outcome of these new ionic liquids were shown to correlate with the change in the nature of the cation.

Predicting solvent effects in ionic liquids: Extension of a nucleophilic aromatic substitution reaction on a benzene to a pyridine

“…Previously, for the reaction between fluorobenzene 1 and ethanol shown in Scheme , the reaction is drawn, omitting the initial pre‐equilibrium typically observed for S N Ar reactions [12a–c, e,18]. Under the conditions used for that reaction, no signals due to the intermediate are observed, and the reaction is first order with respect to the electrophile 1 ; the first step is rate determining.…”

“…At low proportions of ionic liquids 5 and 6 , the rate constant enhancement is entropically driven (due to organisation of the ionic liquid around the pyridine 3 ); however, at higher mole fractions, there is a significant enthalpic contribution (due to favourable ionic liquid‐transition state interactions) that also leads to rate enhancement. For the reaction considered here, the entropic effects dominate; this feature of ionic liquid solvent effects is common to a number of reaction types [11b, c, g,12a,16a,18]…”

“…Through kinetic analyses, our work has shown that ionic liquids can interact with starting materials (at sites including lone pairs[13b,16] and aromatic systems[12b, c]) and also with transition states[10c,12c,17] (particularly those with a significant degree of charge development). This understanding aids in determining what is required for any ionic liquid effect observed and allows for further design of ionic liquids to exploit any such interactions [5b,18]…”

“…An example of a reaction type that is very common in the synthetic literature due to its versatility is the nucleophilic aromatic substitution (S N Ar) reaction . This type of reaction has been examined in ionic liquid solvents . Many of the previously studied S N Ar reactions have used nitrogen‐based nucleophiles; however, one that we have previously examined in ionic liquids is the reaction between 1‐fluoro‐2,4‐dinitrobenzene 1 and ethanol (Scheme ) [12a–c, e]…”

Facile Preparation of Hydrophilic‐Bifunctional‐Groups Modified Magnetic Microspheres as a Novel Matrix for Detection of Phthalate Esters from Human Plasma Samples

“…Recently, ionic liquid‐based MPSE has become research hotspots in the fields of enrichment and separation sciences. Ionic liquids (ILs), consisted of inorganic or organic anions and organic cations, have been widely applied in the fields of separation, catalysis, synthesis and electrochemistry due to the unique features of non‐molecular solvents, designable structural, chemical and electrochemical stability. Ionic liquid‐based MSPE have become a rising star in the field of PAEs analysis.…”