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John W. Elder (1) and Marie A. Paolillo Fairfield University Fairfield, CT 06430
Multistep organic syntheses often are required when direct methods give undesirable byproducts. These multistep processes are challenging but frequently involve procedures and products unfamiliar to students (1). We describe here the synthesis of a relatively simple compound that can be made only indirectly, but uses methods that are both easy to perform and familiar to students.
Direct bromination of aniline produces a variety of polybrominated and oxidized products and direct nitration also leads to oxidized products. Besides this, in acid solution the anilinium ion is formed, and this charged group acts as a deactivator and a meta director. By adding the acetyl group, one arrives at a molecule that does not readily oxidize and substitutes largely at the para position. A second substitution takes place at the position ortho to the carbon carrying the acetamido group. Hydrolysis of the amide function gives the desired 4-bromo-2-nitroaniline.
This sequence has been performed by nearly one hundred students. More than 95% of these have completed the sequence in 33 1/2 h with a reasonable yield of the final product.
PROCEDURE
ACETYLATION
In a 25-mL Erlenmeyer flask is placed 465 mg (5 mmol) of aniline, 12...