Introduction

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 S_N1 (substitution, nucleophilic, unimolecular) and S_N2 (substitution, nucleophilic, bimolecular). Tertiary alcohols follow the S_N1 route, primary alcohols follow the S_N2 route, and secondary alcohols can follow either path.

Under acidic conditions, the mechanism of the S_N1 reaction involves rapid protonation of the alcohol, followed by the loss of water as the rate-determining step. This generates a relatively stable carbocation which is then attacked by the halide ion to form the alkyl halide. S_N1 reactions are favored by tertiary alcohols because they tend to form more stable carbocations.

The product will be verified by gas chromatography by comparing the chromatograms of the starting material, tert-butyl chloride standard, and your product. Confirmation of your product, tert-butyl chloride, can also be performed by reacting the product with a solution of silver nitrate in ethanol. The tertiary alkyl halide will react by means of an S_N1 mechanism with the silver nitrate to form an insoluble silver halide. The appearance of a precipitate indicates a positive result indicating the presence of a tertiary alkyl halide.

Objectives