Preparation Of P-aminobenzotrifluoride

The paper reviews the exploration and the improvement for the preparation of p-nitrotoluene to p-aminobenzotrifluoride . The first step is the conversion of p-nitrotoluene to p-nitrobenzyl bromide. Then it reacts with HF and H2, 99.1% yield of p-aminobenzotrifluoride obtained. The second step is the conversion of p-nitrobenzyl bromide to p-nitrobenzaltribromide by reaction with sodium hypobromite. In the process of the first step it is found that reaction temperature is the most important factor to increase the yield. The yield of p-nitrobenzaltribromide is higher than unimproved one when, with the improvement of equipment, the change of temperature can be controlled in 2 . The second step is a two-phase water-organic solvent system .To give higher yield in a shorter reaction time, phase transfer catalyst (PTC) is applied for 90% (mol) yield. Then p-nitrobenzaltribromide reacts with HF,98% purity of p-nitrobenzotrifuoride obtained. With the catalyst of Ni applied, 97%purity of p-aminobenzotri-Fluoride is obtained. The amine is distilled under reduced pressure. Boiling at 83 (15.8KPa),the purity of p-aminobenzotrifluoride is 99.3%. The yield is 84.3%.The control of process and results of the preparation are illustrated by thin layer chromatography (TLC). The reutilization of bromine , the dispose of bromide are discussed.