Microwave-assisted synthesis of 6,6 '-(aryl(alkyl) methylene)bis(2,4-dialkylphenol) antioxidants catalyzed by multi-sulfonated reduced graphene oxide nanosheets in water

Sulfonated reduced graphene oxide nanosheets (RGO-SO3H) were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and acid-base titration. Multi-SO3H supported on reduced graphene oxide nanosheets was found to be an efficient catalyst for the green synthesis of 6,6'-(aryl(alkyl)methylene)bis(2,4-dialkylphenol) derivatives from 2,4-dialkylphenols and aromatic and aliphatic aldehydes in aqueous media under microwave irradiation. The synthesis of 6,6'-(aryl(alkyl)methylene)bis(2,4-dialkylphenol) derivatives were carried out in the presence of a catalytic amount of RGO-SO3H, under thermal and microwave conditions to afford the desired products in high and excellent yields respectively. In addition, the catalyst could be recovered easily and reused several times without any considerable loss of its catalytic activity.