Transforming Traditional Experiments

One of the best ways I have found to transform a conventional experience into a more inquiry or discovery type format is to diversify the reagents that are used for a synthesis and/or or analyzed by a procedure. That way, students compare their results with those of their classmates (past and present) as part of their lab report. This gives them an opportunity to apply appropriate statistical analysis and identify trends. A good example of this is a recent experiment proposed in JCE where the traditional nitration of ethylbenzoate is expanded to the nitration of several mono-substituted aromatics coupled with analysis of all three possible products: ortho, meta, and para [“Discovering Electronic Effects of Substituents in Nitrations of Benzene Derivatives Using GC-MS Analysis” Clennan & Clennan JCE 84 (2008) p. 1679]. A rather large number of commercial benzene derivatives can be nitrated with concentrated nitric and sulfuric acids by the traditional method. The products are analyzed by GC-MS. This is a nice example of increasing the inquiry value of a traditional experiment. The results of six different starting materials reinforce the directing properties that are espoused by the text book. A couple of anomalies also exist that raise interesting discussion points and prompt further investigations. Nitration of N-Methylaniline produces an appreciable amount of the meta product. Nitration of anisole gives mostly ortho & para disubstituted products. One drawback is that this is much more expensive to buy the necessary chemicals even if they are bought in small amounts. 100g of ethyl benzoate is sold for $19.10. Buying all six of the published starting benzene derivatives in the smallest quantities available from Sigma-Aldrich would cost $122.10.



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