Lab 7: SN1 and SN2 Reactions
In this experiment the purpose of the lab was to study the relationship of structure and reactivity in nucleophilic substitution reactions by using qualitative tests of reactivity. Before the experiment began, students were asked to predict whether the reagents would cause an SN1 mechanism, SN2 mechanism, or both. When predicting the outcome of SN1 and SN2 reactions, the nature of the carbon skeleton, nature of the solvent, and the nature of the leaving group are all taken into account. The experiment called for a two part reaction, sodium iodide in acetone (SN2) and silver nitrate in ethanol (SN1). A series of 8 test tubes were each filled with a different substrate to be tested by these two reagents. Approximately 4 drops of each substrate was added along with 2mL of reagent. If a precipitate was observed, then one can conclude than one of these mechanisms occurred. As shown in the data and observations page, some substrates took part in only one mechanism such as 2-chlorobutane whereas others took part in both mechanisms such as benzyl chloride. During the experiment it was noted that all the substrates besides 2-chlorobutane, t-butylchloride, and Bromobenzene underwent both SN1 and SN2 mechanisms. Our results varied from the predicted outcomes as many of our substrates took on both SN1 and SN2 mechanisms. One possible source of error would be due to the fact that even after vigorously cleaning test tubes and different scientific apparatuses there were still residual contaminants that would affect our results. These contaminants could have caused a faulty precipitate, which would call for incorrect diagnosis of an SN1 or SN2 mechanism.
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