Alkyl halides can be prepared from their corresponding alcohols via an acid catalyzed substitution reaction. The mechanism of these acid catalyzed substitution reactions are labeled as SN1 (substitution, nucleophilic, unimolecular) and SN2 (substitution, nucleophilic, bimolecular). Tertiary alcohols follow the SN1 route, primary alcohols follow the SN2, route and secondary alcohols can follow either path.
The SN2 reaction for converting 1-butanol to 1-bromobutane involves rapid protonation of the alcohol along with a concerted step where the nucleophile attacks the carbon, displacing water. The backside attack by the nucleophile is favored for primary substrates and less ideal for secondary and tertiary substrates.
The product will be verified by gas chromatography by comparing the chromatograms of the starting material, 1-bromobutane standard, and your product. Confirmation of your product, 1-bromobutane can also be performed by reacting the product with a solution of sodium iodide in acetone. The primary alkyl halide will react by means of an SN2 mechanism with the sodium iodide to form an insoluble precipitate. The appearance of a precipitate indicates a positive result suggesting the presence of a primary alkyl halide.
In this experiment, you will
- Synthesize 1-bromobutane via an SN2 reaction.
- Confirm the presence of a primary alkyl halide using the sodium iodide test.
- Verify the product by gas chromatography.