Photocatalytic Hydroxylation of Phenol to Catechol and Hydroquinone by Using Organic Pigment as Selective Photocatalyst

Abstract

Abstract:The application of photocatalytic reactions in organic synthesis has attracted extensive attentions because of recent developments in environmentally benign synthetic processes. For the first time, an organic pigment (C. I. Pigment Green 8) was used as selective photocatalyst to accomplish the photocatalytic hydroxylation of phenol to catechol (CAT) and hydroquinone (HQ) with the assistance of UV irradiation at room temperature. The prepared photocatalysts were characterized by FT-IR spectrum and UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and the result found that the photocatalyst exhibits excellent adsorption ability both in the ultraviolet and visible light region. The effects of various affecting-parameters, such as catalyst amount, H2O2 amount, co-solvents and reaction time, on the photocatalytic hydroxylation of phenol were studied to optimize the reaction conditions. The desired products (CAT and HQ) on the photocatalyst can be facilitated with an increase in the selectivity. In this study, the conversion efficiency of phenol could reach high up to 87.8% with a total selectivity of 73.0% as well as the yield of 37.0% and 27.4% for CAT and HQ, respectively. The reaction is a photo-Fenton like process, and the iron ions cycle between Fe 2+ and Fe 3+ occurs with the light irradiation.

The Synthesis and Utility of Metal-Nitrosophenolato Compounds—Highlighting the Baudisch Reaction

“…Historically, the complexes have featured in a wide range of publications most often-based upon their colourimetric properties, although in recent years, both the metal complexes and their 2-nitrosophenol ligands have received little attention, becoming an almost forgotten class of molecules. However, one compound that has gained current commercial applicability [4] is an iron tris (1-nitroso-2-naphtholato), a dye known as ‘pigment green 8’ (Figure 1) [5,6,7]. This vivid green species has found widespread application in concrete, textiles, paint and rubber colouration.…”