Conversion of t-Amyl Alcohol to t-Amyl Chloride Using HCL
October 27, 2011
Purpose: Alkyl halides can be prepared from alcohols by reacting them with a hydrogen halide, HX (X = Cl, Br, or I). The mechanisms of acid-catalyzed substitution of alcohols are termed SN1 and SN2. The “S” stands for substitution, the “N” stands for nucleophilic, and the “1” or “2” stand for unimolecular or bimolecular. Secondary alcohols react with hydrogen halides by both SN1 and SN2 mechanisms, primary alcohols react by SN2 and tertiary alcohols by SN1. Tertiary alcohols react readily with HX alone to form the alkyl halide, while secondary and primary alcohols require the presence of zinc chloride or heat. In an SN1 reaction, the protonated alcohol loses a water molecule to form a carbocation intermediate in the rate-determining step. The carbocation is then rapidly attacked by the halide ion (X) to form the alkyl halide. Since tertiary alcohols form more stable carbocation intermediates than primary and secondary alcohols, tertiary alcohols are the most likely to follow the SN1 pathway. In SN1 reactions, the formation of a carbocation can lead to rearrangements. Also, elimination to form an alkene can occur.
In this experiment, t-amyl alcohol (2-methyl-2-butanol) in the presence of concentrated HCl will undergo a substitution reaction to form t-amyl chloride.
In order to confirm the presence of a halide, use the Beilstein test. By cleaning a piece of copper wire in a flame, dipping it in the product, and bringing it back to the flame you can see if there is a green color in the flame. If there is a green color in the flame it indicates the presence of a halide. Test the starting material to compare.
Procedure: The procedure for the experiment entitled “Conversion of t-Amyl Alcohol to t-Amyl Chloride Using HCL” is described in Experiments in Organic...