Activation of Alcohols Toward Nucleophilic Substitution: Conversion of Alcohols to Alkyl Halides

The conversion of alcohols into alkyl halides is one of the most important reactions in organic chemistry. Development of new methodology is still desirable in academic research. Unfortunately, the hydroxyl group of the alcohol is relatively difficult to replace under normal conditions. That necessitates the conversion of alcohols to a more activated functionality before nucleophilic substitution becomes viable. Under vigorous conditions, the replacement is straightforward. Procedures for the generation of halides from alcohols have been extensively examined, e.g., using HX or Mitsunobu inversion. However, these methods require time, strong acid, or catalysis to proceed. These classical methods suffer from issues surrounding the toxicity of the reagents used or the difficult purification of the products. This research provided a new technique for promoting nucleophilic chlorination of primary, secondary, and tertiary alcohols by the aromatic cationic activation of the hydroxyl group of the alcohols. The chemical conditions for this transformation are relatively benign and the reaction proceeds rapidly. The kinetics of the reaction were studied by both infrared and ultraviolet-visible spectroscopy. The reaction order was determined and the rate constants were calculated for this halogenation reaction