Reflections on the Teaching Practices for the Reduction of Nitroarenes: Updating Methodologies and Considerations of the Mechanism

Abstract

The reduction of nitroarenes to anilines is a key transformation with real-life context, central to the preparation of many important fine chemicals. The importance of this transformation has led to its inclusion in not only university organic chemistry courses but also preuniversity, especially in Europe. A variety of reagent combinations have been developed to achieve this reduction, each with its own merits; we report herein comparison of the most common methods and what and how this transformation is taught to students. Reviewing preuniversity syllabi and a variety of textbooks, we reveal a misalignment between what is taught and the conditions most commonly used in research. Palladium-catalyzed hydrogenation and iron/ammonium chloride are the most popular reaction choices in the literature, yet these methods are often not mentioned, with other, less general, methods being taught, e.g., tin/concentrated hydrochloric acid, zinc/acid, and lithium aluminum hydride. Where multiple methods are taught, the rationale for inclusion of these is often not presented, particularly considering functional group compatibility, ease of purification, safety, or sustainability. Considering the textbooks reviewed, the mechanisms involved in the reduction are generally not discussed. We argue that, despite the perceived complexity of the reaction, coverage of the sequential nature of the reduction is important in aiding students’ understanding of this reaction, e.g., to account for the formation of various intermediates and/or byproducts. We present suggestions to enable educators to discuss the processes involved in this important transformation, drawing parallels with the presentation of other frequently taught reaction pathways.