1 `-Methyl-2-oxo-5 `-phenylspiro[indoline-3,3 `-pyrrolidine]-4 `,4 `-dicarbonitrile

The title spiro-compound, C(20)H(16)N(4)O, crystallizes with four independent molecules in the asymmetric unit. In all of them, the oxindole unit is planar, the r.m.s. deviations ranging from 0.07 to 0.08 angstrom, while the pyrrolinyl ring adopts an envelope conformation (with the N atom representing the flap). In the crystal, adjacent molecules are linked by N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds

Modified hydroxyethyl cellulose as a highly efficient eco-friendly inhibitor for suppression of mild steel corrosion in a 15% HCl solution at elevated temperatures

Natural polymer-based corrosion inhibitors have been studied for the prevention of steel corrosion in various corrosive environments over recent years, yet they did not show impressive inhibition performance especially at high temperatures. The present study introduces a facile and practical method to enhance the inhibition activity of natural polymers (hydroxyethyl cellulose (HEC) as a carbohydrate model) on the basis of polyurethane chemistry. The ability of chemically modified hydroxyethylcellulose (CHEC) in suppressing mild steel (MS) corrosion was assessed using weight loss, electrochemical impedance spectroscopy (EIS), open circuit potential (OCP), and potentiodynamic polarization (PDP) techniques, and further confirmed by field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). All electrochemical measurements revealed that the incorporation of only 1% of polyurethane prepolymer to the CHEC structure greatly enhanced its inhibition efficiency in the acidic solution, even at high temperatures. CHEC adsorbed on the MS surface and functioned as a mixed-type inhibitor, with a maximum inhibition efficiency of 93% at 80 °C. In addition, the morphology of MS surface in the presence of CHEC confirmed the protective role of the additive and XPS results clearly revealed CHEC adsorption on the MS surface. Furthermore, density functional theory computations and molecular dynamics simulations provided corroborating molecular-level insights on the electronic structure of CHEC and its interactions with the metal surface. These findings demonstrate that the polyurethane prepolymer method is a new and effective approach for enhancing the anticorrosion performance of natural polymer-based corrosion inhibitors in aggressive acidic media at high temperatures