The recent publication of an article on the use of a Grignard reagent in the synthesis of insect pheromones (1) and the subsequent appearance of this experiment in various undergraduate organic laboratory manuals (2-4) stimulated our interest in the preparation of 2-bromopentane, which is the starting material for the above sequence of reactions. Although the cost (5) of 2-bromopentane in the above experiment is not excessive ($1.48/student based upon $24.35/500 g), the educational value of an extension of this synthesis appeared worthwhile.Replacement of a hydroxyl group with a halide is one of the most fundamental reactions in undergraduate organic chemistry yet the efficacy and scope of the reaction is not extensively discussed in most textbooks. Many texts hint at the potential for rearrangement in reactions of secondary halides but only a few detail the significance of the problem (6). In all but primary alcohols substitution is often accompanied by rearrangement, yet textbook examples are typically c This value represents an average yield tor a reaction period of 0.5 h. The yield increases as the period allowed for reaction increases. The reaction period must be kept near 0.5 h if the preparation and purification (by distillation) of 2-bromopentane is to be comfortably completed within one 3-h laboratory session.d Scrupulously anhydrous conditions must be maintained. 9 No 3-bromopentane could be detected by glpc.