CORROSION INHIBITION OF COPPER IN ACID MEDIUM BY DRUGS: EXPERIMENTAL AND THEORETICAL APPROACHES

The inhibition performances of nafcillin (III), methicillin (II) and penicillin G (I) on the corrosion of copper in HCl was studied and tested by weight loss, Tafel polarization, SEM, UV-vis spectrophotometry, molecular dynamics method and quantum chemical calculations. Polarization curves indicated that the studied inhibitors act as mixed-type inhibitors. The values of inhibition efficiency and surface coverage were found to follow the order: Blank ads, indicated that the adsorption of three inhibitors was a spontaneous process. The SEM micrographs confirmed the protection of copper in a 1 M HCl solution by penicillin G, nafcillin, and methicillin. The shape of the UV/vis spectra of inhibitors in the presence of the immersion of Cu showed a strong support to the possibility of the chemisorbed layer formation on Cu surface by nafcillin (between nafcillin and Copper) and physisorption between penicillin and methicillin with copper. DFT calculations were performed to provide further insight into the inhibition efficiencies which were determined experimentally. Molecular dynamics (MD) simulations were applied to find the most stable configuration and adsorption energies of penicillin G, nafcillin and methicillin molecules on Cu (110) surface. The interaction energy followed the order: nafcillin (III)> methicillin (II)> penicillin G (I), which confirmed that nafcillin has the strongest interaction with the metal surface. The obtained results from experimental and theoretical methods were in reasonable agreement. &nbsp

Kinetic investigation of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates and NH-acid such as 7-azaindole by the UV spectrophotometry

783-788Kinetic studies of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of NH-acid, such as 7-azaindole are reported here. Kinetic parameters of the reactions have been monitored by UV spectrophotometery. The second order fits have been automatically drawn and the values of the second order rate constant (k₂) calculated using standard equations within the program. At the temperature range studied, dependence of second order rate constant (Ln k₂) on reciprocal temperature is in agreement with Arrhenius equation. This provides the relevant plots to calculate the activation energy of all reactions. Studies on the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates) and also concentration of reactants on the rate of reactions have been made. Proposed mechanism has been confirmed according to the obtained results and steady state approximation and first step (k₂) of reaction recognized as the rate determining step on the basis of experimental data