Synthesis and structure of 4-methyl-1-N-(p-tolyl)imidazole as organic corrosion inhibitor

ABSTRACT

Heterocyclic organic compounds containing nitrogen, sulfur or oxygen atoms are often used to protect metals from corrosion acting as organic corrosion inhibitors. Their inhibiting role is based on excellent ligand abilities and formation of stabile metal complex. Two requirements are essential for using selected class of organic inhibitors: (a) ligand capacity in the conditions of corrosion such as atmospheric conditions, acid or neutral corrosion, etc., and (b) nontoxicity, i.e., environmentally friendly inhibitors. Imidazole derivatives are capable to fulfil both requirements and they are, from that point of view, very promising and profound class of ligands. Synthesis and X-ray diffraction molecular and crystal structure of 4-methyl-1-N-(p-tolyl)imidazole has been reported, since it exhibits the most prominent corrosion inhibiting role. The synthesis, starting from 4-methylimidazole and 4-bromotoluene, is based on Ullmann-type coupling reaction by applying modifications of N-arylation by arylhalogenides and Cu₂O as an efficient catalyst.

The molecular and crystal structure of prepared N-substituted imidazole derivative reveals non-planar molecular conformation and the supramolecular assembling of the molecules via C-H···N intermolecular hydrogen bonds between C_sp2-H proton donor groups and basic imidazole nitrogen atom. The molecules are related by a 2₁ screw axis parallel to [0 1 0] in the form of infinite C(4) zig-zag 1D chains via C-H···N intermolecular hydrogen bonds. Such alignment produces additional weak stacking interaction between imidazole and phenyl ring of related chains.

GRAPHICAL ABSTRACT

The synthesis of efficient copper corrosion inhibitor, 4-methyl-1-N-(p-tolyl)imidazole starting from 4-methylimidazole and 4-bromotoluene and Cu₂O as a simple and efficient catalyst, has been reported. The molecules are assembled into infinite C(4) zig-zag 1D chains via C-H···N intermolecular hydrogen bonds. Such alignment produces additional weak stacking interaction between imidazole and phenyl ring of related chains.

KEYWORDS:

• Imidazole derivatives
• organic corrosion inhibitor
• synthesis
• X-ray single crystal diffraction

Acknowledgments

We are grateful to the Ministry of Science and Technology of the Republic of Croatia for the financial support under the project 125-1252973-2572. The authors thank the staff of the Central Analytical Servis for elemental analyses and Laboratories for NMR of the Institute “Ruđer Bošković” for recording of the NMR spectra. The authors wish to thank prof. Mario Cetina, PhD, for X-ray data collection.