International Journal of Chemistry

International Journal of Chemistry | Vol. 6, No. 10, October 2015 | pp. 73–80

DOI: 10.46882/2015/IJC/000085

Article Type: Original Research Paper

Title: Kinetic Studies and Isotope Effects of the Permanganate Oxidation of L-Phenylalanine in Acidic Medium

Names of Authors: T. M. Usman¹, F. M. Al-Rasheed²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Saud University, Riyadh, Saudi Arabia.

Abstract: The kinetics of transition metal electron transfer processes involving amino acids yield essential data required to map biochemical oxidation paths and intermediate radical formations. The oxidation of L-phenylalanine by permanganate ions (MnO₄⁻) was investigated spectrophotometrically in an aqueous sulfuric acid medium at a constant ionic strength of 0.20 M (Na₂SO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of MnO₄⁻ at its wavelength maximum of 525 nm. The empirical rate law showed a first-order dependence on [MnO₄⁻] and a fractional-first-order dependence on [L-phenylalanine]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway driven by the active protonated permanganate species, HMnO₄. Variations in ionic strength produced negligible kinetic shifts, indicating a rate-determining step involving a neutral molecule and an ionic species. Stoichiometric determinations confirmed that 5 moles of L-phenylalanine consumed 2 moles of permanganate, producing phenylacetaldehyde and Mn(II) ions as the primary end products. Thermodynamic activation constants calculated from temperature-dependence datasets using the Eyring equation yielded an enthalpy of activation (delta H*) of 45.8 kJ/mol and an entropy of activation (delta S*) of -112.4 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Permanganate oxidation; L-phenylalanine; Activation parameters; Reaction mechanisms

Manuscript Timeline: Received: March 15, 2015; Revised: May 20, 2015; Accepted: July 02, 2015; Published: October 05, 2015.

Citation: Usman, T. M., & Al-Rasheed, F. M. (2015). Kinetic Studies and Isotope Effects of the Permanganate Oxidation of L-Phenylalanine in Acidic Medium. International Journal of Chemistry, 6(10), 73–80.

International Journal of Chemistry | Vol. 6, No. 2, February 2015 | pp. 9–16

DOI: 10.46882/2015/IJC/000077

Article Type: Original Research Paper

Title: Mechanochemical Optimization and Sulfation Resistance of Metakaolin-Gyratory Slag Geopolymer Cements in Marine Environments

Names of Authors: T. S. Ani¹, A. M. L. Gonçalves²*

Authors’ Affiliations:
¹Department of Electronic and Chemical Engineering, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Civil Engineering, University of Coimbra, Coimbra, Portugal.

Abstract: Concrete infrastructure exposed to marine conditions suffers heavy degradation due to seawater sulfate attacks, requiring the development of resistant binders. This research details the structural design and chemical resistance of binary geopolymer cements synthesized via the alkaline activation of metakaolin integrated with electric arc furnace slag (EAFS) at substitution levels ranging from 0% to 50%. Activation parameters were optimized using a mixture of sodium silicate and 14 M sodium hydroxide. Durability metrics were monitored by immersing cured specimens in 5% magnesium sulfate (MgSO₄) solutions for 180 days. Structural phase shifts were mapped utilizing X-ray diffraction (XRD), FT-IR spectroscopy, and Scanning Electron Microscopy (SEM). Compressive strength testing showed that geopolymer specimens prepared with 30% slag maintained a high compressive strength of 48.5 MPa post-immersion, suffering a minimal strength reduction (< 4.2%). XRD analyses confirmed the complete absence of expansive ettringite and gypsum minerals, which typically ruin standard Portland cement structures. SEM imaging revealed a highly dense crosslinked gel network, proving that these geopolymers are excellent alternative materials for marine infrastructure.

Keywords: Geopolymer; Metakaolin; Electric arc furnace slag; Sulfate resistance; Compressive strength; Microstructure

Manuscript Timeline: Received: April 10, 2014; Revised: May 22, 2014; Accepted: June 18, 2014; Published: February 06, 2015.

Citation: Ani, T. S., & Gonçalves, A. M. L. (2015). Mechanochemical Optimization and Sulfation Resistance of Metakaolin-Gyratory Slag Geopolymer Cements in Marine Environments. International Journal of Chemistry, 6(2), 9–16.

International Journal of Chemistry | Vol. 7, No. 5, May 2016 | pp. 33–40

DOI: 10.46882/2016/IJC/000092

Article Type: Original Research Paper

Title: Biochemical Assessment, Functional Properties, and Mineral Fingerprinting of Underutilized Cereal Grains from West Africa

Names of Authors: A. E. Ogunkoya¹, A. M. O. R. de Sousa²*

Authors’ Affiliations:
¹Department of Chemistry, Ekiti State University, Ado-Ekiti, Nigeria.
²Department of Food Science, National Institute of Health Dr. Ricardo Jorge, Lisbon, Portugal.

Abstract: Underutilized indigenous cereal grains serve as resilient agricultural reservoirs in arid zones, yet detailed mapping of their dietary matrices is required to expand their commercial adoption. This research evaluates the proximate nutritional composition, functional properties, and mineral mineral profile of three underutilized West African grains (Digitaria exilis, Pennisetum glaucum, and Eragrostis tef) gathered during the dry season harvest. Proximate analysis established high total carbohydrate contents ranging from 68.4% to 74.2% on a dry weight basis, alongside significant crude protein profiles (9.2% to 12.8%) and very low crude lipid levels (1.5% to 2.4%). Mineral profiling using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) revealed that iron and zinc were highly concentrated within D. exilis fractions (5.4 mg/100g and 3.8 mg/100g respectively), while toxic heavy metals remained well below international safety benchmarks. Quantified antinutritional matrices showed exceptionally low baseline concentrations of tannins (0.12 to 0.24 mg/g) and phytic acid (1.15 to 1.84 mg/g). Functional parameter tracking confirmed high water absorption capacities and stable gel formation limits, proving that these grains are excellent dietary matrices for developing gluten-free infant weaning formulations.

Keywords: Underutilized cereals; Proximate composition; Mineral profile; Antinutrients; Digitaria exilis; Gluten-free matrices

Manuscript Timeline: Received: October 18, 2015; Revised: November 28, 2015; Accepted: January 05, 2016; Published: May 04, 2016.

Citation: Ogunkoya, A. E., & de Sousa, A. M. O. R. (2016). Biochemical Assessment, Functional Properties, and Mineral Fingerprinting of Underutilized Cereal Grains from West Africa. International Journal of Chemistry, 7(5), 33–40.

International Journal of Chemistry | Vol. 6, No. 12, December 2015 | pp. 89–96

DOI: 10.46882/2015/IJC/000087

Article Type: Original Research Paper

Title: Green Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Fruit Peel Extract of Citrus aurantifolia

Names of Authors: M. A. Haruna¹, S. Swaminathan²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Madras, India.

Abstract: The utilization of toxic synthetic chemical inhibitors in industrial acid descaling operations creates substantial environmental and safety hazards, driving research into sustainable green alternatives. The corrosion mitigation performance of the methanolic fruit peel extract of Citrus aurantifolia (CA-Extract) on carbon steel in 1.0 M HCl was investigated via gravimetric weight loss and electrochemical test protocols. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were recorded across varying inhibitor dosages (0.2 to 2.0 g/L) and system temperatures (303 to 333 K). Weight loss metrics revealed that protection efficiency increased with extract concentration, peaking at 92.5% at a dose of 2.0 g/L. Polarization diagrams established that CA-Extract functions as a mixed-type inhibitor, suppressing both anodic iron dissolution and cathodic hydrogen gas evolution pathways. EIS scans confirmed that charge-transfer resistance (Rct) increased with higher extract amounts, indicating the formation of a robust organic protective film on the steel face. The adsorption behavior of the bioactive compounds conformed to the Langmuir isotherm model, yielding a negative standard free energy of adsorption (delta G°ads = -21.4 kJ/mol), denoting a spontaneous physical adsorption mechanism driven by the presence of rich plant flavonoids.

Keywords: Carbon steel; Corrosion inhibition; Citrus aurantifolia; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: April 18, 2015; Revised: June 05, 2015; Accepted: July 12, 2015; Published: December 04, 2015.

Citation: Haruna, M. A., & Swaminathan, S. (2015). Green Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Fruit Peel Extract of Citrus aurantifolia. International Journal of Chemistry, 6(12), 89–96.

International Journal of Chemistry | Vol. 6, No. 5, May 2015 | pp. 33–40

DOI: 10.46882/2015/IJC/000080

Article Type: Original Research Paper

Title: Synthesis, Microcharacterization, and Antileishmanial Activity of Novel Artesunate Transition Metal Complexes

Names of Authors: A. A. Yusuf¹, S. K. Das²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Pharmaceutical Sciences, Jadavpur University, Kolkata, India.

Abstract: The systemic spread of drug-resistant protozoal vectors requires the structural modification of classic sesquiterpene lactone frameworks via coordination to transition metal ions to enhance lethal cellular targeting. This study reports the synthesis, microcharacterization, and in vitro biological evaluation of novel copper(II), zinc(II), and iron(II) complexes coordinated with artesunate ligands. The newly synthesized structures were characterized using elemental analysis, molar conductance, magnetic susceptibility, and FT-IR spectroscopy. Analytical metrics established a 1:2 metal-to-ligand ratio, corresponding to the molecular formula [M(ART)₂Cl₂], where ART represents the deprotonated artesunate drug. Molar conductance values in DMF confirmed non-electrolytic properties. FT-IR spectra established that the drug coordinates in a bidentate manner, binding to the metal cores via the lactone carbonyl and the deprotonated carboxylate oxygen atoms. In vitro antileishmanial susceptibility testing was executed against Leishmania donovani promastigotes using the Alamar Blue assay. The iron(II)-artesunate complex demonstrated high lethal potency, yielding an IC50 value of 1.42 μM compared to standalone uncoordinated artesunate (6.84 μM). This enhanced performance is driven by metal-induced homolytic cleavage of the peroxide bridge, accelerating free radical generation inside the parasite cells.

Keywords: Artesunate; Metal complexes; Coordination chemistry; Antileishmanial activity; Leishmania donovani; Free radicals

Manuscript Timeline: Received: June 05, 2014; Revised: July 18, 2014; Accepted: August 20, 2014; Published: May 04, 2015.

Citation: Yusuf, A. A., & Das, S. K. (2015). Synthesis, Microcharacterization, and Antileishmanial Activity of Novel Artesunate Transition Metal Complexes. International Journal of Chemistry, 6(5), 33–40.

International Journal of Chemistry | Vol. 6, No. 7, July 2015 | pp. 49–56

DOI: 10.46882/2015/IJC/000082

Article Type: Original Research Paper

Title: Adsorptive Elimination of Cadmium(II) Ions from Industrial Effluents Using Xanthated Coconut Coir Matrices

Names of Authors: E. N. Chidi¹, M. H. van den Bosch²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands.

Abstract: Heavy metal contamination of surface waters due to battery manufacturing operations presents severe ecological risks due to the toxicity and mobility of cadmium compounds. This study explores the adsorptive performance of modified coconut coir prepared via chemical modification with carbon disulfide in alkaline media (xanthation). The surface morphology and chemical modifications of the adsorbent were studied using scanning electron microscopy (SEM) and FT-IR spectroscopy. The analytical data confirmed that xanthation successfully integrated sulfur-rich dithiocarbonate groups onto the cellulosic biomass network. Batch extraction experiments evaluated parameters of solution pH, contact time, adsorbent dosage, and initial Cd(II) concentrations. Maximum Cd(II) adsorption occurred at an optimum pH of 6.0, using an equilibrium contact period of 90 minutes. Equilibrium data fit the Langmuir model closely, showing a maximum monolayer adsorption capacity of 58.45 mg/g at 298 K. Sorption kinetics followed a pseudo-second-order model with a high correlation coefficient (R² > 0.997), proving that chemical surface complexation reactions controlled the mass transfer rates. Thermodynamic constants showed that the adsorption process was spontaneous (delta G° = -5.12 kJ/mol) and endothermic, establishing xanthated coir as an affordable material for wastewater treatment plant designs.

Keywords: Coconut coir; Chemical modification; Xanthation; Cadmium removal; Adsorption kinetics; Chemisorption

Manuscript Timeline: Received: January 20, 2015; Revised: March 02, 2015; Accepted: April 10, 2015; Published: July 05, 2015.

Citation: Chidi, E. N., & van den Bosch, M. H. (2015). Adsorptive Elimination of Cadmium(II) Ions from Industrial Effluents Using Xanthated Coconut Coir Matrices. International Journal of Chemistry, 6(7), 49–56.