physiology 209
1
SN2 Reaction, Ionic Liquid (Group – hood)
Background Reading
Solomons and Fryhle Chapter 6 (Substitution/Elimination Reactions)
Techniques: Weights and Measures, Reflux, Liquid-Liquid
Extraction, Distillation.
Introduction
The SN2 reaction is a bimolecular nucleophilic substitution reaction where the nucleophile (a molecule with a free pair of electrons) reacts with an alkyl halide and replaces the halogen (for more details see Solomons and Fryle, Chapter 6). The nucleophile approaches the carbon bearing the halogen from the back side. As the reaction proceeds, a bond begins to form between the nucleophile and the carbon while the bond between the carbon and the halogen begins to break (this is the transition state). The reaction is complete when a covalent bond has formed between the nucleophile and the carbon and the halogen has been removed as a halide ion. This process is accompanied with an inversion of stereochemistry at the targeted carbon center.
In this experiment, our nucleophile is 1-methylimidazole and we will use it to attack 1-bromobutane (our alkyl halide) to form 1butyl-3-methylimidazolium bromide. We will refer to this molecule as [C4−mim]Br, C4 referring to the 4 carbon units, mim referring to the methylimidazole unit, and Br to the bromide counter ion. After an anion exchange reaction, you will form [C4-mim]PF6, which is a well-known ionic liquid.
Most ionic compounds (salts) have very high melting points
(>500 °C); however, ionic liquids are a unique subset of salts that melt at temperatures below 100 °C and can even be liquids at room temperature. Ionic liquids can be very useful as alternative solvents because of their negligible vapour pressure, low combustibility, and high thermal stability. Traditional solvents, such as ether and hexane, have high vapour pressures (evaporate readily). In addition, the fumes are an irritant (cause dizziness and headaches) and are highly flammable. Therefore, the use of
SN2 Reaction, Ionic Liquid (Group – hood)
Background Reading
Solomons and Fryhle Chapter 6 (Substitution/Elimination Reactions)
Techniques: Weights and Measures, Reflux, Liquid-Liquid
Extraction, Distillation.
Introduction
The SN2 reaction is a bimolecular nucleophilic substitution reaction where the nucleophile (a molecule with a free pair of electrons) reacts with an alkyl halide and replaces the halogen (for more details see Solomons and Fryle, Chapter 6). The nucleophile approaches the carbon bearing the halogen from the back side. As the reaction proceeds, a bond begins to form between the nucleophile and the carbon while the bond between the carbon and the halogen begins to break (this is the transition state). The reaction is complete when a covalent bond has formed between the nucleophile and the carbon and the halogen has been removed as a halide ion. This process is accompanied with an inversion of stereochemistry at the targeted carbon center.
In this experiment, our nucleophile is 1-methylimidazole and we will use it to attack 1-bromobutane (our alkyl halide) to form 1butyl-3-methylimidazolium bromide. We will refer to this molecule as [C4−mim]Br, C4 referring to the 4 carbon units, mim referring to the methylimidazole unit, and Br to the bromide counter ion. After an anion exchange reaction, you will form [C4-mim]PF6, which is a well-known ionic liquid.
Most ionic compounds (salts) have very high melting points
(>500 °C); however, ionic liquids are a unique subset of salts that melt at temperatures below 100 °C and can even be liquids at room temperature. Ionic liquids can be very useful as alternative solvents because of their negligible vapour pressure, low combustibility, and high thermal stability. Traditional solvents, such as ether and hexane, have high vapour pressures (evaporate readily). In addition, the fumes are an irritant (cause dizziness and headaches) and are highly flammable. Therefore, the use of