Characterization of newly synthesized pyrimidine derivatives for corrosion inhibition as inferred from computational chemical analysis F. El-Taib Heakal a , S.A. Rizk b , A.E. Elkholy c, * a Chemistry Department, Faculty of Science, Cairo University, 12613 Giza, Egypt b Chemistry Department, Faculty of Science, Ain Shams University, 11566 Cairo, Egypt c Department of Analysis and Evaluation, Egyptian Petroleum Research Institute,11727 Cairo, Egypt article info Article history: Received 9 August 2017 Received in revised form 19 September 2017 Accepted 21 September 2017 Available online 25 September 2017 Keywords: Corrosion inhibitors Pyrimidine derivatives Spectroscopic methods Quantum calculations Monte Carlo abstract Corrosion of metallic constructions is a serious problem in most industries worldwide that can be controlled via addition of special chemicals having adsorption capability on metal surfaces and hence isolating it from the aggressive environment. These chemicals are characterized by being rich in func- tional groups containing free lone pairs of electrons and/or p-electrons. In the present study four newly imidazole-pyrimidine based ionic derivatives have been synthesized and their structures were charac- terized by means of elemental analysis and different spectroscopic techniques. Quantum chemical cal- culations were carried out to give insights into the structural and electronic characteristics of these fabricated compounds. Monte Carlo simulation was also applied to shed the light on our prepared corrosion inhibitor molecules by examining their aptitude to adsorb on iron surface. Our ultimate goal is to help industries in fighting corrosion by providing them with a cheap and efficient anti-corrosion molecules. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Carbon steel has attracted much attention as structural material in transmission pipelines or storage vessels in oil and gas produc- tion systems as it is non-expensive metal and has excellent me- chanical properties [1e4]. Corrosion is described as the natural deterioration of metallic materials by the action of its aggressive surrounding medium [5]. Corrosion problems can lead to serious risks for plant integrity, reduce plant efficiency and cause plant shut-down and losses in addition to the contamination by noxious products [1,6]. Among the most corrosive media are acids (e.g. HCl and H 2 SO 4 ) and brine solutions (e.g. sea water and formation wa- ter). The aggressiveness of these media can be mitigated via adding special chemicals having the ability to adsorb on metal surface and hence isolating it from the corrosive environment. These corrosion retarding substances or inhibitors [1] can be classified according to their chemical nature into inorganic, organic or hybrid inhibitors [7,8]. The most common corrosion inhibitors are organic com- pounds containing hetero atoms (e.g. O, N and S) and/or multiple bonds or aromatic rings (p-systems) which are effective for inhibiting metal corrosion [9,10]. Their inhibitive action proceeds via adsorption of their molecules on the metal surface displacing adsorbed water molecules at the interface forming subsequently a compact barrier film [11,12]. This film can deter metal corrosion by reducing the anodic and/or the cathodic process rate. Availability of non-bonded electrons (free lone pairs) and/or p-electrons in an inhibitor molecule facilitates the electron transfer from the inhib- itor to the metal surface forming coordinate covalent bonds be- tween inhibitor molecules and metal atoms at its surface [13e15]. Imidazole-pyrimidine based ionic compounds have the char- acteristics of thermal stability [16], relatively high ionic conduc- tivity, wide electrochemical window [17] and amphoteric behavior in solution [18]. Such ionic compounds retain their stability up to 230  C due to their quaternized amine, aromatic nature of the rings and intermolecular hydrogen-bonding [16]. Their amphoteric behavior in solution is attributed to the imidazole-pyrimidine rings which can equally accept and donate protons. This allows the linkage with alkyl substituents using facile SN 2 reactions at the 3- ring position. The 1-position on the ring is a secondary amine, which undergoes a variety of reactions. Furthermore, in the pres- ence of a strong base, the 2-position is deprotonated. Additionally, the imidazolium cation is associated with a mobile counter anion of * Corresponding author. E-mail addresses: aymanesmat2015@gmail.com, aymanesmat2015@epri.sci.eg (A.E. Elkholy). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2017.09.079 0022-2860/© 2017 Elsevier B.V. All rights reserved. Journal of Molecular Structure 1152 (2018) 328e336