Quantum Design and Synthesis of a Gasoline Marker Based on a Phenol‐Functionalized Supramolecular Quaternary‐Salt Complex

Abstract

AbstractWe present the development of supramolecular surfactants (SSs) based on MR⋅⋅⋅OA⋅⋅⋅(PhOH)i complexes among methylene red (MR), oleyl amine (OA) and stoichiometric amounts of phenol (PhOH), aimed at obtaining markers for the identification of gasolines by harnessing their supramolecular interactions‐mediated stability and homogeneous distribution within gasoline, as well as their very‐characteristic nuclear magnetic resonance (NMR), Fourier‐transform infrared (FTIR), and UV‐visible (UV‐vis) signals. Density functional theory (DFT), together with the conductor‐like screening model (COSMO), reveal that the supramolecular interactions are due to a non‐ionic to ionic reaction under which the carboxylic proton is transferred from MR to OA, and that PhOH confers solubility to SSs withing gasoline by hiding their ionic heads. The proton transference was confirmed by 1H NMR and 13C NMR, FTIR, and thermogravimetric analysis spectroscopies, whereas the solubility in gasoline through UV‐vis absorbance measurements that, together with viscosity measurements, also revealed that the maximum content of PhOH for adequate performance is 3, in agreement with DFT‐COSMO calculations, which predict that for 3 the SSs’ interaction energy per additional PhOH becomes weaker. All theoretical and experimental results support the viability of MR⋅⋅⋅OA⋅⋅⋅(PhOH)i complexes as gasoline markers due to their full compatibility with gasoline and their well‐defined spectroscopic‐fingerprints.