Senior Investigators: Prof. Wes Borden (U. North Texas), Prof. John Hartwig (UI-UC), Prof. William Jones (U. Rochester)

Aniline is produced on a billion pound per year scale as a starting material for many chemicals including dyes, polyurethane and other plastics, herbicides and specialty fibers. The current synthesis of aniline relies on old, well- known chemistry that has been optimized. To further improve upon the synthesis, new chemistry must be developed; our approach attempts to combine the efforts of computational chemistry to direct the ‘wet’ chemistry towards the goal of an environmentally friendly synthesis of aniline from readily available, inexpensive starting materials.

The simplest and most direct synthesis of aniline from benzene would use ammonia as the source of nitrogen, however this type of reaction is not thermodynamically favored. Replacement of ammonia with hydroxylamine alters the reaction such that it is very thermodynamically favorable, but no catalyst is currently known that will allow this reaction to happen quickly enough to be industrially useful.

The strategy employed by our group was to begin with a series of computational model catalysts that were evaluated on a theoretical basis; the best catalyst candidates are undergoing evaluation with various conditions. The initial guesses as to what a good catalyst would look like allowed the screening of a vast array of compounds in a timely manner. Catalysts based on a ligand bound to a metal allowed both changes of the metal and ligand to be examined. The variations in structure and function of these calculated catalysts and the experiments they inspired are expected to lead to a useful catalyst that will also give insight into fundamental chemical processes.

By using various hydroxylamine derivatives containing a phenyl group complements the development of the intrinsically less favored direct synthesis of aniline. The use of these hydroxylamine derivatives should give three primary results. (1) the synthesis of N-heterocycles (analogues of aniline), (2) reaction mechanisms should be easier to study with these compounds than with the process involving hydroxylamine and benzene, (3) catalysts that work for this system should provide direction as to the design of a catalyst for hydroxylamine-benzene system.

We are working to develop a catalyst that will allow the environmentally friendly synthesis of aniline using the top reaction shown. The currently used industrial synthesis of aniline is shown in the bottom reaction and requires the use of expensive and dangerous materials and harsh conditions, and creates significant amounts of hazardous waste.