Question

In this laboratory experiment, you will synthesize a RTIL, 1-hexyl-3-methylimidazolium hexafluorophosphate, using a two-step process involving nucleophilic substitution and anion exchange. 1-Hexyl-3-methylimidazolium hexafluorophosphate and its structural analogs have long names. Therefore, they are often abbreviated as [Cn-mim X, where n = the number of carbons in the alkyl chain of the cation, ‘mim' stands for methylimidazolium and X = the anion. P -N N N-methylimidazole - NON » neat A A H2O, rt - KBr ENT + Br 1-bromohexane Br [Ce-mim]Br PFE [Co-mim]PF6 + KPF6 UNDERSTANDING THE EXPERIMENT In the first step of this reaction, N-methylimidazole and 1-bromohexane are mixed "neat” meaning that no solvent is employed. With heating, a nucleophilic substitution reaction occurs to yield [Co- mim Br which possesses a Group A anion and is water-soluble. In the second step of the reaction, water is added to dissolve [C6-mim]Br and KPF, is added to convert [Co-mim]Br to [Co-mim]PF. The byproduct of this step is KBr. Because [Co-mim]PF. possesses a Group B anion, it is significantly less soluble in water than is [Co-mim]Br, and it can be isolated by extraction with dichloromethane followed by removal of dichloromethane by distillation. This two-step procedure is operationally simple and typically high yielding, but often RTILs prepared in this way are contaminated by halide salts, e.g., KBr. These salts may affect the physical properties of the RTIL and efforts must be made to remove the halide contaminant from the desired RTIL.

QUESTION: Draw an arrow-pushing mechanism for the FIRST STEP of this synthetic sequence.

Answer 1

Answer terms metin Deat en Bro Mechanisms Bro