This laboratory experiment was developed to provide a safe, economical, and effective way to instruct undergraduate organic chemistry students about the unimolecular nucleophilic substitution (S[subscript N]1) reaction. Students treat 2,5-dimethyl-2,5-hexanediol with excess concentrated hydrochloric acid to synthesize 2,5-dichloro-2,5-dimethylhexane, assess solubility of the starting material and the product in different solvents, and determine purity with thin-layer chromatographic analysis. The experiment was performed by approximately 97 students. The effectiveness of the laboratory was assessed by two separate methods: a qualitative postlab student self-assessment and a quantitative prelab and postlab three-point quiz. For the qualitative student self-assessment, the students stated that they acquired an improved understanding of the S[subscript N]1 reaction from the experiment. The average on the quantitative prelab and postlab quiz increased from 0.80 [plus or minus] 0.86 to 1.69 [plus or minus] 1.02 and demonstrated a statistically significant improvement. The percentage of students who were able to correctly identify the S[subscript N]1 reaction mechanism increased from 22.9% to 46.5% from the prelab quiz to the postlab quiz and further to 74.2% on the midterm exam. (Contains 2 tables, 3 figures and 1 note.)