Synthesis and characterization of bidentate esters by green methodology

Abstract

The synthesis of organic compounds through environmentally safer routes constitutes one of the main current challenges in Chemistry, due to the significant impact associated with the use of toxic solvents and harsh reaction conditions. In this context, the present work focused on the synthesis of aromatic esters derived from phenolphthalein and α-naphtholphthalein, employing the Schotten-Baumann method. The study was based on the question of the feasibility of obtaining these aromatic esters through a more sustainable synthetic route, as well as the influence of structural modification of the starting materials on the characteristics of the products formed. Thus, the general objective was to synthesize and characterize phenolphthalein dibenzoate (EL1) and α-naphtholphthalein dibenzoate (EL2), using aqueous medium, room temperature, and the absence of organic solvents. Specifically, the aim was to obtain the compounds through reaction with benzoyl chloride, compare the products with the starting materials, and elucidate their structures. The work was grounded in the principles of Green Chemistry and employed, as methodological procedures for characterization, melting point determination, thin-layer chromatography (TLC), infrared spectroscopy (IR), and proton and carbon-13 nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR). The results indicate successful formation of the desired compounds, with EL2 presenting a novel structure and satisfactory yields. The technique proved to be simple, low-cost, and fully aligned with several principles of Green Chemistry.