Study New Pyridine Derivatives as Corrosion Inhibitors for Mild Steel in an Acidic Media

Some new pyridinium salts, namely4-(4-bromo-benzylidene-hydrazinocarbonyl)-1-phenyl-pyridinium bromide, A1; 4-(4-bromo-benzylidene-hydrazinocarbonyl)-1-butyl-pyridinium bromide, A2; 4-(4-bromo-benzylidene-hydrazinocarbonyl)-1-phencyl-pyridinium bromide, A3; were synthesized and studied as corrosion inhibitors for mild steel in 1M H2SO4aqueous solution at 20°C by weight loss measuring for 24 hrs. The results showed that the inhibition efficiency of all pyridinium bromide derivatives had a significant in value with the highest concentration. An increase in the inhibitor concentration is accompanied by a decrease in the corrosion rate, an increase in the retarding efficiency and an increase in the degree of surface coverage. The values of the free energy of adsorption revealed the effects of spontaneously reaction of (A1, A2, and A3) and gave useful information to predict the interaction between the metal surface and the organic molecules as corrosion inhibitors.

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

A wide range of derivatives with new pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline skeleton was synthesized by free-radical intramolecular cyclization of o-bromophenyl-substituted pyrrolylpyridinium salts using the (TMS)3SiH/AIBN system. The cyclization provides generally good yields of pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline hydrobromides having no additional radical-sensitive substituents. The free bases can be obtained from the synthesized hydrobromides in quantitative yield by basification at room temperature. The selectivity control of intramolecular arylation was achieved by replacing the halogen: the use of 1-(2-(ortho-bromophenyl)-4-(ortho-iodophenyl)pyrrol-3-yl)pyridinium bromide makes it possible to obtain a monocyclization product, and the bicyclization product from the dibromo derivative. The procedure is also applicable to obtain 3-arylpyrido[2,1-a]pyrrolo[3,2-c]isoquinoline derivatives including 2-unsubstituted skeletons that are inaccessible via Pd-catalyzed cyclization.

Synthesis New Pyridinium Salts as Corrosion Inhibitors for Mild Steel in 1 M H2SO4

Some new pyridinium salts, namely 4-(4-Chloro-benzylidene-hydrazinocarbonyl)-1-phenyl-pyridinium bromide, C1; 4-(4-Chloro-benzylidene-hydrazinocarbonyl)-1-butyl-pyridinium bromide, C2; 4-(4-Chloro-benzylidene-hydrazinocarbonyl)-1-phencyl-pyridinium bromide, C3; were synthesized and Corrosion inhibitors for mild steel were tested in a 1M H2SO4aqueous solution at 20ºC for 24 hours using weight loss measurements. The findings revealed that the inhibition efficiency of all pyridinium bromide derivatives converges at the maximum concentration. An increase in inhibitor concentration is associated with a decrease in corrosion rate, an increase in inhibition efficiencies, and an increase in surface degree of coverage. The physisorption effects for (C1, C2, and C3) were revealed by the free energy values of adsorption, which provided useful information for predicting the interaction between the metal surface and organic molecules as corrosion inhibitors.

Efficient Synthesis of Tetra- and Penta-substituted Benzenes via Domino Cycloaddition Reaction of pyridinium ylide and Chalcone o-Enolate

A very simple and high efficient synthetic protocol for tetra- and penta-substituted benzene derivatives has been provided by tetramethylguanidine (TMD) promoted reaction of 4-(N,N-dimethylamino)-1-phenacyl-pyridinium bromide with chalcone o-enolates in DMF...

Impact of Degree of Hydrophilicity of Pyridinium Bromide Derivatives on HCl Pickling of X-60 Mild Steel: Experimental and Theoretical Evaluations

Dodecyl pyridinium bromide (DDPB), tetradecyl pyridinium bromide (TDPB) and dodecyl 1,1′-bispyridinium dibromide (DDBPB) were successfully synthesized, characterized and evaluated for HCl pickling of X-60 low carbon steel. Order of corrosion inhibitions efficiencies, as revealed by both electrochemical and gravimetric studies, is TDPB > DDPB > DDBPB. The degree of hydrophilicity of inhibitors as predicted by a partition coefficient (Log P) and supported by a contact angle measurement was found to be responsible for their order of corrosion inhibition efficiencies. Adsorption of DDPB, TDPB, and DDBPB through the pyridinium nitrogen on mild steel surface was confirmed by ATR-FTIR and SEM-EDX analyses. The pyridinium nitrogen was found not to be the only factor responsible for their efficiency, but hydrophobes and the orientation of the hydrophilic ring were responsible, which incline to the deviation of experimental results and the order of Monte Carlo simulation adsorption energies. DDPB, TDPB, and DDBPB obey the Langmuir isotherm model despite major contributions of the film formed on the surface of X-60 mild steel on their overall inhibition corrosion resistance.