© Division of Chemical Education •  www.JCE.DivCHED.org •  Vol. 86 No. 7 July 2009  •  Journal of Chemical Education 853 In the Laboratory Substitution reactions are valuable teaching tools in the un- dergraduate classroom. hey teach students the fundamentals of organic reactivity and provide the foundation for understanding many organic reaction mechanisms. S N 1 reactions are particu- larly useful for imparting students with a solid understanding of carbocations, including their stability, resonance, and ability to rearrange. Despite the utility of these reactions for explaining the basis of reactivity, there are few examples in the educational literature. Background Experiments that demonstrate the use of an S N 1 reaction for the synthesis of ethers exist (1, 2). Procedures for the acid- catalyzed ether formation of ethyl t-butyl ether (1) and Methyl Diantilis, a fragrance (2), are available from this Journal. Al- though these experiments provide options for implementing a S N 1 reaction, there are drawbacks to both procedures. he ethyl t-butyl ether synthesis requires the use of sulfuric acid and the isolation of the ether involves both a distillation and a liquid–liquid extraction. he fragrance is available from vanillin in two steps. However, the irst step is a sodium borohydride reduction reaction of an aldehyde, which is oten addressed much later than substitution reactions in the course curriculum. In addition, the analysis of the fragrance involves both 1 H NMR and IR spectroscopy, which is usually performed in the second semester of the laboratory. here are a number of experiments that look at the forma- tion of carbocations to determine the stability of the carbo- cation or the rate of formation of the carbocation (3–7). A semi-empirical and DFT computational experiment has been reported that looks at the dissociation of alkyl halides to show the order of stability of alkyl substituted carbocations (3). he analysis of the dissociation of alkyl halides is valuable in terms of reinforcing the stability of cations, but there is no hands-on synthesis involved in this laboratory. Many of the published solvolysis experiments are designed to measure the rate of car- bocation formation (4–7). hese are good experiments for a physical chemistry laboratory, but they do not allow students to experience the isolation of the solvolysis products, which is an important part of the learning process. Rationale here is a lack of experiments available for the S N 1 reaction that meet the following criteria: short reaction times, easy prod- uct isolation, easy product puriication, high yields, relatively benign reagents (no strong acids or strong lachrymators), and no competing reactions. Owing to the utility of S N 1 reactions in providing a strong foundation for understanding organic reactivity, a new laboratory was developed that would allow the students to apply the optimal conditions for a solvolysis reaction. he reaction of bromodiphenylmethane is quick (7), and it was anticipated that bromotriphenylmethane would un- dergo reaction more readily and quickly, due to the additional stability associated with a tertiary carbocation that is highly resonance stabilized (8). In addition, bromodiphenylmethane is a lachrymator whereas bromotriphenylmethane is not. Bromo- triphenylmethane was chosen as a substrate because it dissoci- ates quickly to generate a stable carbocation intermediate and allows the reaction to occur in a reasonable time. In addition, triphenylmethanol and many triphenylmethyl ethers are solids, which would allow the students to isolate a product, determine the melting point for product conirmation, and highlight the solvolysis of a tertiary substrate. he triphenylmethyl cation is well known for its stability. It is commercially available from Sigma–Aldrich as the tetra- luoroborate salt. One method for the generation of the highly colored cation is the treatment of triphenylmethanol with a strong acid, such as luoroboric acid or sulfuric acid (9). Also, substituted triphenylmethyl cations are dyes that are used for wool and silk (10), which provides relevance for this experience to everyday life. Experiment Bromotriphenylmethane (1.6 mmol) 1 is added to acetone then a large excess of water or the appropriate alcohol is added. he reaction to generate triphenylmethanol 2 and the remaining triphenylmethyl ethers is almost instantaneous. Ph Ph Ph Br Ph Ph Ph OR H: R = 2 Me: 3 Et: 4 1-Pr: 5 1-Bu: 6 1 ROH he reaction to generate triphenylmethanol 2 and the remain- ing triphenylmethyl ethers is almost instantaneous. he process of monitoring the reaction by GC–MS shows that even ater 1 minute, no bromotriphenylmethane remains in the reaction mixture. Product isolation is straightforward for triphenylmeth- anol 2, triphenylmethyl methyl ether 3, and triphenylmethyl ethyl ether 4 (9); the addition of the reaction solution to ice causes the product to crystallize and precipitate from solution so that it may be collected by suction iltration. he crude product is recrystallized from 2-propanol. In the cases of the 1-propyl ether 5 and 1-butyl ether 6, the product must be extracted from the aqueous solution with dichloromethane and concentrated to give a solid product. A Flexible Solvolysis Experiment for the Undergraduate Organic Laboratory John J. Esteb, John R. Magers, LuAnne McNulty,* Paul Morgan, Kathryn Tindell, and Anne M. Wilson Department of Chemistry, Butler University, Indianapolis, IN 46208; *lmcnulty@butler.edu