Solvent-Free Synthesis of Azo Dyes Based on β-Naphthol Using Nano-γ-Al2 O3 /Ti(IV) by Grinding Method

Abstract

Azo compounds in addition to common uses in science and technology, is used as optical materials in the processing of molecular data, ion sensors, and biological applications. Primary aromatic amines are diazotized in an acid, and the subsequent coupling process can produce azo dyes. Supported Ti(V) catalyst is a powerful Lewis acid that is used to promote organic reactions. In this work, azo dyes were effectively synthesized using Nano-γAl2 O3 /Ti(IV) as a solid acid reagent. The heterogeneous nanoparticles were fully characterized by FT-IR, XRD, XRF, EDS, TGA, FESEM, TEM and BET techniques. This solid acid reagent enhances the coupling reaction of β-naphthol with aryl diazonium salt to form diazo dyes under solvent free grinding conditions. In this protocol, many aromatic amines with electron withdrawing or electron releasing groups are used to form azo dyes. Azo dye products are characterized by FT-IR and NMR spectroscopy. This new synthetic method has the advantages of short reaction times, easy work-up and high yields.