Introducing selective electro-oxidation of aryl and alkyl sulfides protocol in a novel environmentally friendly media
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ORIGINAL PAPER
Introducing selective electro‑oxidation of aryl and alkyl sulfides protocol in a novel environmentally friendly media Ghodsiyeh Sadat Ferdowsi1 · Majid Jafarian1 · Vahid Khakyzadeh1 Received: 25 November 2019 / Accepted: 9 June 2020 © Iranian Chemical Society 2020
Abstract Since derived products from the oxidation of sulfides are vital for pharmaceutical companies, in this paper, electro-oxidation of aryl and alkyl sulfides was investigated on the glassy carbon electrode (GC) by electrochemical techniques such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). To choose the best electrolyte, electro-oxidation of organic sulfides was investigated in different solutions such as ethanol, propanol, acetone, acetonitrile, and acetic acid. Among them, acetic acid not only did not have the pesky peak but also produced the largest oxidation current with increasing sulfide. In the following, studies were carried out to optimize the percentage of acetic acid and sodium hydroxide solution as a supporting electrolyte and oxygen source, which eventually a mixture of 85:15 acetic acid and solution of 1 M NaOH had the best oxidation efficiency. It should be noted, this effective media is introduced and reported for the first time. Then, the electro-oxidation of several sulfides were investigated in the optimized electrolyte. Kinetic studies were performed on the introduced system and several kinetic data were determined for methyl phenyl sulfide electrochemical oxidation. Finally, a mechanism for the electro-oxidation of sulfide was proposed. Keywords Sulfides electro-oxidation · Electro-catalyst · Glassy carbon electrode · Organic sulfide
Introduction The development of pharmaceutical precursor synthesis and especially biologically active sulfoxides are very important for pharmaceutical companies because not only are they used in medicine and pharmacy but also are the best-selling medications [1]. For example, esomeprazole, employed to heal peptic ulcer disease, aprikalim consider as an antihypertensive drug, and oxisurane is well-known as an immunosuppressor (Fig. 1) [2]. In recent years, designing an affordable and environmentally friendly process has been of great interest to researchers for the production of sulfoxide and researchers have always tried to use green catalysts, oxidants, and solvents to produce it. Likewise, oxidation of sulfides is vital in controlling water and environmental pollution [3–5]. Recently, many researchers use hydrogen peroxide as an oxidizing agent, because of low price and cleanliness. * Majid Jafarian [email protected] 1
Department of Chemistry, K. N. Toosi University of Technology, Tehran, Iran
However, hydrogen peroxide alone does not perform well and along with it, some acids should be used as activators. In chemical oxidation methods, although the use of homogeneous catalysts has good efficiencies, their separation is very difficult [6]. Therefore, many researchers have used heterogeneous methods and used solid
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