Scielo RSS <![CDATA[South African Journal of Chemistry]]> vol. 66 num. lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Optimization of experimental parameters in preparing multinanoporous TiO<sub>2</sub> thin films by the anodic oxidation method</b>]]> The anodic oxidation method has been applied to the preparation of multinanoporous TiO2 thin films. The experimental parameters, including the electrolyte nature, oxidation voltage, and oxidation time have been carefully controlled. Their influence on the structure, morphology and photocatalytic activity of the prepared TiO2 films has been evaluated by measuring the current density. The result showed that there was a relatively wide range of preparation conditions, and the internal relationship between the structure and the photocatalytic properties of the TiO2 films was analyzed. <![CDATA[<b>Quantification of rhodium in a series of inorganic and organometallic compounds using cobalt as internal standard</b>]]> An analytical method for the quantification of rhodium using inductively coupled plasma optical emission spectrometry (ICP-OES) and cobalt as internal standard was developed. Rhodium recovery was determined in different samples, which included a certified reference material (CRM), pure rhodium metal, inorganic RhCl.3H2O salt as well as different organometallic compounds. Excellent rhodium recoveries of 100,100, 99.0 and 99.7 % with relative standard deviations (RSD) of 1.0,1.0, 0.3 and 0.4 % were obtained for the CRM, rhodium metal sample, RhCl3·3H2O and [Rh(cupf)(PPh3)(CO)(CH3)(I)], respectively. The accurate recovery of rhodium was, however, affected by the presence of easily ionized elements (EIE) and unmatched acid matrixes with a decrease in rhodium recovery of up to 16 %. Validation parameters such as accuracy, precision, specificity, limit of detection (LOD) and robustness were all investigated to confirm the suitability of this newly developed analytical procedure for rhodium determination. <![CDATA[<b>Amorphous Pt@PdCu/CNT catalyst for methanol electrooxidation</b>]]> A multi-walled carbon nanotube-supported, Pt decorated nano-sized amorphous PdCu alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a galvanic displacement reaction. The structure is examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical activity of the Pt@PdCu/CNT catalyst is tested by cyclic voltammogrametry (CV) and compared to that of PtRu/CNT catalysts. The results show that amorphous Pt@PdCu/CNT catalyst exhibits better electro-catalytic performances for methanol oxidation than its crystalline counterpart. <![CDATA[<b>Investigation into the aroma of rosemary using multi-channel silicone rubber traps, off-line olfactometry and comprehensive two-dimensional gas chromatography-mass spectrometry</b>]]> Multi-channel polydimethylsiloxane rubber traps were used to sample the headspace of rosemary samples (two essential oils from different sources, one oleoresin and one dried herb) followed by comprehensive two-dimensional gas chromatography -time of flight mass spectrometry (GCxGC-TOFMS) or GC-MS analyses. The aroma of different headspace samples was characterized using a custom-built olfactory apparatus. The differences between the aroma profiles were evident from bubble plots of the perceived aroma at different temperatures. The samples were heat-treated to simulate cooking of food products, and were then reassessed to determine any changes in the aroma profile. It was found that the intense menthol and cooling aromas subsided in all the samples with heating. GCxGC-TOFMS allowed for separation of the numerous components in the headspace samples. Many terpenes and aliphatics were thus tentatively identified and the relative peak areas were compared to better understand the mixture that contributes to the rosemary aroma. <![CDATA[<b>Synthesis and crystal structure of ethyl 2-(benzo[<i>d</i>]oxazol-2-yl)-5-oxo-3-(<i>o-</i>tolylamino)-2,5-dihydroisoxazole-4-carboxylate</b>]]> The title compound ethyl 2-(benzo[d|oxazol-2-yl)-5-oxo-3-(o-tolylamino)-2,5-dihydroisoxazole-4-carboxylate (5) was synthesized and studied by the single crystal X-ray diffraction method. Its structure was confirmed by IR, ¹H and 13C NMR spectroscopy, microanalyses, and X-ray single crystal structure determination. Compound 5 crystallized in the monoclinic system, space group P2(1)/c, a = 11.9936(3) Å, b = 13.9638(3) Å, c = 11.5126(4) Å, α = γ = 90°, β = 108.939(3) °, V = 1823.70(9) ų,Z = 4, R1 = 0.050 and wR2 = 0.130. Compound 5 shows an intramolecular hydrogen bond between N9-H...O3 atoms. The H-bond and donor-acceptor (N9...O3) distances were obtained 2.165 and 2.798 Å, respectively. The crystal structure of 5 also shows a weak interaction between O1 and O26 atoms with distance of 2.985 Å. The benzo[d]oxazole and o-toluidine rings moieties are not collimated together on isoxazolone ring. The torsion angles of N9-C8-N7-C17, O6-N7-C17-O18 equal -49.63 ° and 68.67 °, respectively. <![CDATA[<b>Adsorptive removal of malachite green with activated carbon prepared from oil palm fruit fibre by KOH activation and CO<sub>2</sub> gasification</b>]]> The adsorptive potential of activated carbon prepared by chemical activation from oil palm fruit fibre (OPFAC) to remove malachite green (MG) dye from its aqueous solution was investigated in this study. The OPFAC prepared was characterized by means of BET, TGA, FTIR, pHpzc, elemental analysis and Boehm titration. Operational parameters such as pH, adsorbent dose, contact time, initial dye concentration and temperature were studied in batch process. It was found that OPFAC has a larger surface area and total pore volume than commercially activated carbon. The adsorption process attained equilibrium in 45 minutes. Equilibrium data were tested by using two isotherm models: Langmuir and Freundlich. It was found that adsorption of MG on OPFAC correlated well with the Langmuir isotherm model with a maximum monolayer adsorption capacity of 356.27 mg g-1. The kinetics of the adsorption process was tested by means of pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The pseudo-second-order kinetic model provided the best correlation for the experimental data studied. The adsorption process is controlled by both the boundary layer and intraparticle diffusion mechanisms. The thermodynamic study showed that the process is endothermic, spontaneous and feasible. Cost analysis revealed that OPFAC is 20 times cheaper than commercially available activated carbon. <![CDATA[<b>Negishi coupling of pteridine-O-sulfonates</b>]]> Negishi coupling of pteridine-O-sulfonate with Zn-aryls is reported. Hydrolysis of the protecting groups with 1M NH3 gave the 6-subustituted 2,4-diaminopteridine while hydrolysis with 1 M NaOH gave the 6-subsituted pterin. <![CDATA[<b>Microwave-assisted synthesis of some 1<i>H</i>-1,2,4-triazol-3-one derivatives</b>]]> 4-Amino-5-(methyl/ethyl)-2,4-dihydro-3H-1,2,4-triazol-3-one were synthesized from the reaction of (methyl/ethyl)-ester ethoxycarbonyl hydrazone with hydrazine hydrate and then, converted to corresponding Schiff bases using 9H-fluorene-3-carbaldehyde. Ester, hydrazide and oxadiazole derivatives were synthesized starting from Schiff bases in three steps. All reactions occurred under conventional conditions and microwave irradiation. The obtained results were compared. <![CDATA[<b>A novel coumarin Schiff-base fluorescent probe for Mg<sup>2+</sup></b>]]> A novel fluorescent probe for Mg²+ based on coumarin Schiff-base was synthesized and characterized. The sensor displayed high selectivity toward Mg²+ in acetonitrile, and shows 1:1 complex formation with Mg²+ in acetonitrile. <![CDATA[<b>Carbonyl substitution in β-diketonatodicarbonyl-rhodium(I) by cyclo-octadiene: Relationships with experimental, electronic and calculated parameters</b>]]> The substitution rate constant of the reaction between [Rh(β-diketonato)(CO)2] and cyclo-octadiene is related to various empirical parameters and density functional theory calculated energies and charges, β-diketonato = R'COCHCOR. Results indicate that especially the Hammett meta substituent constants (σ), the Lever electronic parameters (E L) and the density functional theory calculated energies and charges predict the substitution rate constant to a high degree of accuracy, for example: ln k2 = 8.48 (σr + σr,) - 2.24 (R² = 0.99) = 31.8 ΣEl - 63.0 (R² = 0.99) = - 9.16 E HOMO - 52.1 (R² = 0.97) = 101 ΣQ Mulliken(Rh(CO)2) - 49.9 (R² = 0.99). <![CDATA[<b>Synthesis of novel bibrachial lariat ethers (BiBLEs) containing [1,2,4]triazolo[3,4-<i>b</i>][1,3,4]thiadiazines</b>]]> A practical and regioselective method for the synthesis of cis-diastereomers of bibrachial lariat ethers (BiBLEs) bearing ester and amide groups is reported. The novel bibrachial lariat ethers (BiBLEs) 3a-d with neutral side chains were preparedby reaction of the corresponding aza-crown macrocycles 1a-b with ethyl chloroacetate and chloroacetamide. <![CDATA[<b>Terpyridyl complexes as antimalarial agents</b>]]> A number of transition metals and their terpyridyl complexes have been evaluated for antimalarial activity on the strain 3D7. The metals, ligands and complexes were each in turn investigated for their efficacy. All activities were in the sub-micromolar range (0.1-1 µM). Their modes of action were compared with that of chloroquine to discover whether or not they were capable of inhibiting haemozoin formation. The data indicate that efficacy could be a result of several mechanisms and that speciation of the metal complex and the manner in which the agents are added to the parasitic broth have a profound effect on the activity of the agents. We believe that our study offers a template by which other researchers should approach their experiments using transition metal complex agents. <![CDATA[<b>An electrochemical investigation of methanol oxidation on nickel hydroxide nanoparticles</b>]]> In this work, a nickel-modified glassy carbon electrode (GCE) was prepared using a potentiostatic method in 0.1 M acetate buffer solution at pH 4.0 containing 1.0 mM nickel nitrate. Nickel hydroxide nanoparticles were prepared using consecutive potential scanning in 0.1 M NaOH solution. The as-prepared catalyst was characterized by field emission scanning electron microscopy and electrochemical methods. Electrochemical characterization exhibited stable redox behaviour of the Ni(III)/Ni(II) couple. Cyclic voltammetric experiments showed that electrocatalytic oxidation of methanol can occur at the modified electrode, whereas it is not observed at a bare GCE. The effect of potential sweep rates and methanol concentration on its electrochemical behaviour was studied. The rate constant (k) for the chemical reaction between methanol and catalytic centres has been evaluated by chronoamperometry. In addition, long-term stability of the modified electrode was investigated by electrochemical methods. <![CDATA[<b>Acidic brønsted ionic liquids catalyzed the preparation of 1-((benzo[<i>d</i>]thiazol-2-ylamino)(aryl)-methyl)naphthalen-2-ol derivatives 1-[(1,3-benzothiazol-2-ylamino)(aryl)methyl]-2-naphthol</b>]]> The acidic ionic liquids, triethylammonium hydrogen sulfate ([Et3NH]HSO4), 2-pyrrolidonium hydrogen sulfate ([Hnhp]HSO4), 3-methyl-1-sulfonic acid imidazolium chloride ([Msim]Cl), and 1-methylimidazolium hydrogen sulfate ([Hmim]HSO4) catalyzed three-component condensation reaction of aromatic aldehydes, 2-aminobenzothiazole, and β-naphthol to afford corresponding 1-((benzo[d]thiazol-2-ylamino)(aryl)-methyl)naphthalen-2-ol derivatives. The inexpensive and non-toxic ionic liquids can be reused several times without noticeable loss of their activities. <![CDATA[<b>Halogenated oxindole and indoles from the South African marine ascidian <i>Distaplia skoogi</i></b>]]> The known 3,6-dibromoindole (1), 6-bromo-3-chloroindole (2) and 6-bromo-2-oxindole (3) were isolated from the marine ascidian (sea squirt) Distapia skoogi collected from Algoa Bay, South Africa. Standard spectroscopic techniques were used to elucidate the structures of 1-3. All three compounds were found to be moderately cytotoxic to metastatic MDA-MB-231 breast cancer cells. <![CDATA[<b>Fabrication and antibacterial performance of nano-silver-doped monoliths by the sol-gel method</b>]]> The organic-inorganic hybrids of glycine, tetraethylortho silicate (TEOS) and triethylphosphate (TEP) doped with silver ions were prepared by the sol-gel method. After moulding and heating at 600 °C to remove organic compound, porous Ag/P2O5-SiO2 monoliths were obtained. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrum, transmission electron microscopy (TEM), infrared spectroscopy (FT-IR) and scanning tunnelling microscopy (STM) were used to structurally study monoliths. Surface area, pore volume and swelling degree of the samples were adjusted with different contents of TEP in the starting composition. Ag ions were stably released into the water at 30 °C for 28 days. Antibacterial experimentation revealed that such materials, treated at 600 °C, could restrain Escherichia coli effectively. <![CDATA[<b>Conformational preferences of Amphibian peptides Brevinin-Ya and Brevinin-Yb explored using molecular dynamics</b>]]> The brevinin-1 family peptides obtained from different frog skins have great potency against bacterial and fungal infections. Their biological activities are significantly affected by mutations especially at positions 11 and 14. However, despite having great medicinal potential, the detailed information regarding their three-dimensional structures is still not fully known. In the present study, the conformational profiles of two brevinin peptides (Brevinin 1-Ya and Brevinin 1-Yb) were explored at molecular mechanics level using molecular dynamics (MD) method. Specifically, four MD simulations (Brev1_Ya(E), Brev1_Yb(E), Brev1_Ya(H), Brev1_Yb(H)) were performed starting from extended as well as helical conformations of both peptides under implicit solvent conditions. The analysis of the results indicated that both peptides have a strong tendency to attain α-helical character, preferably from their central residues extending towards their C-terminals12-23, whereas their N-terminal residues stay either in β-turn or extended forms. However, the extent of helicity was comparatively lower in Brevinin 1-Ya, irrespective of its starting structure in the simulations, and like other factors such as cationicity and hydrophobicity, could be related to the biological activity profiles of these peptides. <![CDATA[<b>Synthesis, characterization and antibacterial activity of imidazole derivatives of 1,10-phenanthroline and their Cu(II), Co(II) and Ni(II) complexes</b>]]> Six new CuL¹ (L¹ = 4-bromo-2-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenol), CoL¹, NiL¹, CuL² (L² = 2-(1H-imidazo[4,5-f] [1,10]phenanthroline-2-yl)-5-methoxyphenol), CoL² and NiL² complexes were synthesized. L¹ and L² ligands were prepared by the condensation of 1,10-phenanthroline-5,6-dione with 5-bromosalicylaldehyde and 2-hydroxy-4-methoxybenzaldehyde, respectively. The structures of the compounds were determined by elemental analyses, IR, UV-visible, ¹H-NMR, TGA, magnetic susceptibilities and molar conductance measurements. It is observed that the synthesized complexes have tetragonal and distorted square pyramidal geometrical structures. Antibacterial activity of the ligands and their metal complexes were tested against selected bacteria by disc diffusion method. <![CDATA[<b>Palygorskite hybridized carbon nanocomposite as a high-performance electrocatalyst support for formic acid oxidation</b>]]> A nanocomposite, in which acid-treated palygorskite was hybridized with carbon, was prepared and designed as an efficient support for electrocatatlysts. Pd nanoparticles were deposited on the hybrid support as an electrocatalyst for formic acid oxidation. The hybrid supports and electrocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TEM and XRD results showed that acid treatment had an effective impact on the morphology of palygorskite, but did not destroy its architecture. XPS results indicated that the introduction of palygorskite resulted in a negative shift of binding energy of Pd deposited on it. The electrochemical results showed that the addition of palygorskite into the carbon facilitated the formation of OHads or Oads on the surface of Pd/C-PLS, and further improved the formic acid electrooxidation activity. Therefore, considerable improvements in electrocatalytic activity toward formic acid oxidation was achieved by using this hybrid support when compared with conventional carbon support, suggesting that the introduction of SiO2-based porous palygoriskite was an excellent and cost-efficient way to improve the electrocatalytic performance of carbon support. <![CDATA[<b>Thermal behaviour and detonation characterization of N-benzoyl-3, 3-dinitroazetidine</b>]]> N-benzoyl-3,3-dinitroazetidine(BDNAZ) is a derivative of 3,3-dinitroazetidine (DNAZ). Its thermal behaviour was studied by DSC methods. The results show that there are one melting process and two exothermic decomposition processes. The kinetic parameters of the intense exothermic decomposition process were obtained from the analysis of the DSC curves. The apparent activation energy, pre-exponential factor and the mechanism function are 170.77 kJ mol-1,10(14.12) s-1 and f(α) = (1-a)-1/2, respectively. The specific heat capacity of BDNAZ was determined with a continuous Cp mode of a micro-calorimeter. The standard mole specific heat capacity of BDNAZ was 286.31 J mol¹ K-1 at 298.15 K. Using the relationship between Cp and T with the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion, tTIAD), the self-accelerating decomposition temperature (TSADT), thermal ignition temperature (T TIT), critical temperatures of thermal explosion (Tb) and period of validity (t0.9) were obtained to evaluate its thermal safety. The detonation velocity (D) and pressure (P) of BDNAZ were estimated by using the nitrogen equivalent equation according to the experimental density. <![CDATA[<b>Synthesis of Alkyne and Alkene Ketal Derivatives of Pentacyclo[<sup>2,6</sup>.0<sup>3,10</sup>.0<sup>5,9</sup>]undecane-8-11-dione and 1-Phenyl-pentacyclo[<sup>2,6</sup>.0<sup>3,10</sup>.0<sup>5,9</sup>]undecane-8-11-dione</b>]]> Functionalizingpentacyclo[,6).0(3,10).0(5,9)]undecane-8-11-oneand 1-phenyl-pentacyclo[,6).0(3,10).0(5,9)]undecane-8-11-one can be easily accomplished by using the alcohols of various alkynes and alkenes. Generally the synthesis of terminal alkyne and cyclic alkene ketal derivatives were performed fairly easily. Synthesis of the terminal alkenes provided some difficulties. Reduction of the alkyne ketal derivatives using Pd/CaCO3 has been demonstrated to form a mixture containing the desired alkene ketal derivatives. <![CDATA[<b>The Development and Refinement of a Questionnaire on the Investigation of Students' Experience of First-Year Chemistry Practicals</b>]]> This article reports on the development and refinement of a questionnaire for first-year Chemistry students. Three subscales were probed, namely affective attitudes, perceptions towards tutor effectiveness and outcomes achieved. <![CDATA[<b>Zn(BH<sub>4</sub>)<sub>2</sub>/2NaCl: A novel reducing system for efficient reduction of organic carbonyl compounds to their corresponding alcohols</b>]]> Zn(BH4)2/2NaCl, obtained by the reaction of ZnCl2 and NaBH4 ,is a stable, efficient and selective reducing system in dry-THF. The Zn(BH4)2/2NaCl system (0.5-1 mmol) reduces a variety of carbonyl compounds to their corresponding alcohols in CH3CN at room temperature in high to excellent yields. <![CDATA[<b>One-pot, facile synthesis of quinoxaline derivatives from bis-aryl </b><b>α</b><b>-hydroxyketones and <i>o</i>-arenediamines using KMnO<sub>4</sub>/CuSO<sub>4</sub></b>]]> KMnO4/CuSO4, a readily available reagent combination, was found to be effective for the high-yield synthesis of quinoxaline derivatives from bis-aryl o-hydroxyketones and o-arenediamines in hot ethanol. <![CDATA[<b>Adsorption of dyes using different types of sand: A review</b>]]> The threat posed by increasing amount of dyes on daily basis, especially on our ecosystem, has brought a serious search for more efficient low-cost adsorbents. Sand is mixed with cement and water to make concrete, used in the manufacture of brick, glass and other materials, and it can also be used as a medium for the filtration of water. Sand, which is ubiquitous, has been used as an adsorbent because of its enormous availability in the local environment. This review reveals that further research must be conducted to bring to the fore the expansive laboratory, industrial and environmental usage of sand materials as dye adsorbents. Consequently, the usage of different types of sand in the field of adsorption science represents a viable and powerful tool, resulting into the superior improvement in pollution control and environmental preservation. <![CDATA[<b>Synthesis and biological evaluation of novel thiosemicarbazone-triazole hybrid compounds as antimalarial agents</b>]]> A novel series of thiosemicarbazone-triazole hybrids were efficiently synthesized and evaluated for their activity against the 3D7 strain of the malaria parasite, Plasmodium falciparum. Although the hybrids were found not to be as potent as the standard chloroquine, they have shown activities interesting enough to warrant future structure activity relationship (SAR) studies. <![CDATA[<b>The synthesis and sharacterization of several corroles</b>]]> Preliminary results towards the synthesis of a corrole-based vitamin B12 analogue are reported. The synthesis of three simple corroles, 5,10,15-triphenylcorrole (TPCrl), 5,10,15-tri(2-nitrophenyl)corrole and 10-(4-methoxyphenyl)-5,15-diphenylcorrole is described. The synthesis of 10-[2-(benzoylamino)phenyl]-5,15-diphenylcorrole (DPAPCrl) suggests that a large, bulky meso substituent can be incorporated into the corrole with no loss of stability or significant decrease in yield. Both TPCrl and DPAPCrl were crystallized and their crystal structure is reported. <![CDATA[<b>Intermolecular interactions and thermodynamic properties of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide dimers: A density functional theoretical study</b>]]> Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imaginary frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected binding energy among the three dimers is -42.38 kJ mol-1. The charge redistribution mainly occurs on the adjacent O(N)......H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cºp), entropies (S°m) and enthalpies (H°m)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature. <![CDATA[<b>Decoration of multi-walled carbon nanotubes by metal nanoparticles and metal oxides using chemical evaporation method</b>]]> The powder patterns of the as-prepared and acid treated MWCNTs are shown by the XRD spectra. The TEM results show the microstructure of the multi-walled carbon nanotubes well decorated with metal nanoparticles (Cu, Fe, Ni) and metal oxides (CuO, Fe2O3 NiO), while the SEM show the surface morphology. <![CDATA[<b>A simple three-component synthesis of 3-amino-5-arylpyridazine-4-carbonitriles</b>]]> New 3-amino-5-arylpyridazine-4-carbonitriles have been synthesized by a one-pot three-component reaction of malononitrile with arylglyoxals in the presence of hydrazine hydrate at room temperature in water and ethanol. <![CDATA[<b>Extraction of pesticides from plants using solid phase microextraction and QuEChERS</b>]]> A study employing dispersive solid phase extraction in the form of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method and solid phase microextraction (SPME) for the cleanup of pesticides in plant samples from the Okavango Delta (Botswana) is presented. Concentration levels of aldrin, 1,1-dichloro-2,4-bis[chlorophenyl]ethane (DDD), 1,1-dichloro-2,2-bis[p-chlorophenyl]ethylene(DDE), 1,1,1-trichloro-2,2-bis[p-chlorophenyl]ethane (DDT), dieldrin, endosulfan and endrin were investigated using gas chromatography with electron capture detection (GC-ECD) and confirmed with gas chromatography with high resolution time of flight mass spectrometry (GC-TOFMS). Parameters affecting the extraction efficiencies of both techniques were optimized. In the absence of CRMs for the plants under investigation, method validation and evaluation of the extraction efficiencies were achieved through spiking of Nymphaea nouchali (Tswii) leaves at two concentration levels with trichlorobenzene as an internal standard. Recoveries for both SPME and QuEChERS were in the range 61-95 %. The calibration plots were reproducible and linear (R² > 0.995) with limits of detection ranging from 0.102 to 1.693 µg L-1 for all the pesticides. The optimal conditions for QuEChERS and SPME were applied to the extraction of pesticides residues from the edible parts (leaves, roots and/ or stems) of Asparagus africanus, Cleome hirta and Nymphaea nouchali plants. No pesticides were detected in the leaves and stems of all the plants studied. Aldrin and endosulfan were detected in the Nymphaea nouchali roots at concentrations of 3-21 µg kg-1 and 5-3 µg kg-1, respectively. Pentachlorobenzene (PCB) and hexachlorobenzene (HCB) were also detected but were not quantified. <![CDATA[<b>Measuring the impact of academic development courses in first- and second-year chemistry</b>]]> This paper uses multivariate analysis to estimate the impact of educational interventions in the first-year academic development chemistry courses on students' final course marks. The cohorts for seven years are pooled, which generates a more robust set of results than was previously the case. To counter the sample-selection problem that arises as academic development students are placed onto the academic development programme, a selection of control variables is included in the estimations. The results suggest that the educational interventions in the first year had a positive impact on academic development students' performance, relative to mainstream students, in both the first- and second-year courses. The implications of the results for education policy and research are considered. <![CDATA[<b>Densities and excess molar volume for the ternary systems (1-butyl-3-methylimidazolium methyl sulphate + nitromethane + methanol or ethanol or 1-propanol) at T = (303.15 and 313.15) K</b>]]> The densities of the ternary systems containing the ionic liquid 1-butyl-3-methylimidazolium methyl sulphate ([BMIM]+[MeSO4]-) were determined. The ternary systems studied were ([BMIM]+[MeSO4]- + nitromethane + methanol or ethanol or 1-propanol) at the temperatures (303.15 and 313.15) K. The ternary excess molar volumes were calculated from the experimental densities at each temperature, being negative for all mole fractions of the ionic liquid. The minimum ternary excess molar volumes increase with an increase in temperature for the systems ([BMIM]+[MeSO4]- + nitromethane + methanol or ethanol), and decrease for the system ([BMIM]+ [MeSO4]- + nitromethane + 1-propanol). The results are interpreted in terms of the alcohol chain length and the intermolecular interactions. <![CDATA[<b>Making ET AAS determination less dependent on vapourization kinetics of the analytes</b>]]> The quantification of the analytes in ET AAS is normally attained by the measurement and integration of transient absorbance. High degree of atomization and constant vapour transportation rate for the analyte atoms in the absorption volume are considered to be crucial to grant correctness of the measurements. However, the second of these conditions has, in fact, never been met in the commercial tube or tube-platform ET atomizers. The vapourization of the analyte occurs during temperature rise that affects vapour transport; vapourization temperature depends on matrix or presence of chemical modifier. In the analytical practice, the problem is normally bypassed by using reference materials with physical and chemical properties similar to those of the sample. The general solution of the problem comes from the integration of running absorbance normalized with regard to vapour transportation velocity. In this work, the approach was verified by measuring absorption signals for Ag, Cd, Mn, Pb and Tl in the tube atomizer (without a platform), monitoring the temperature of the tube and calculating the instantaneous velocity of vapour transfer and respective integration. The semi-empirical formula employed to describe vapour transport velocity included the diffusion parameters specific for each element and a common constituent, attributed to gas expansion. The measurements and numerical integration were performed using various temperature ramps for the analytes alone and those introduced together with excessive amounts of Mg and Pd. The methodology suggested reduced the error associated with change of atomization kinetics from 20 to 2 %. In combination with chemical modification the measurement methodology does not require platform atomization. <![CDATA[<b>Hydrogenation of cinnamaldehyde over an ionic cobalt promoted alumina-supported palladium catalyst</b>]]> Nano γ-alumina-supported transition metal-based mono- (Pd0/γ-Al2O3 or CoIII/γ-Al2O3) and bimetallic catalysts (Pd0CoIII/γ-Al2O3), were prepared by wet impregnation, oxidation and in situ reduction of the palladium. The palladium(II) acetate [PdII3(OOCCH3)6], cobalt(II) acetate [CoII(OOCCH3)2].4H2O and palladium, cobalt bridging tetraacetate [PdII CoII(OOCCH3)4].H2O.2CH3COOH, were used as catalyst precursors to prepare a 7.4 % mol catalyst/support loading. The oxidation states of these activated catalysts were studied by XPS. These catalysts were evaluated for hydrogenation of cinnamaldehyde in a biphasic reaction under 3 MPa of hydrogen at 80 °C. The Pd0/γ-Al2O3 selectively catalyzed the hydrogenation of C=C bond in cinnamaldehyde to form phenylpropanol (100 %). In contrast, catalysis with Pd0CoIII/γ-Al2O3 hydrogenated both C=C and C=O bonds consecutively, forming 65 % phenylpropanal and 35 % phenylpropanol with TOF = 47.2 h-1. No reaction occurred when CoIII/γ-Al2O3 was used. <![CDATA[<b>The Vibrational Spectra of the Boron Halides and Their Molecular Complexes. Part 14. <i>Ab Initio</i> Studies of the Boron Trifluoride-Nitrous Acid Complex</b>]]> A number of electron donor-acceptor complexes formed between boron trifluoride and nitrous acid have been studied, in order to ascertain which of the interacting monomers acts as the acid and which as the base. We have found four complexes in which electron donation occurs in the direction HONO νBF3. These complexes are bound through the hydroxyl O, the N and the nitrosyl O atoms, in decreasing order of strength of interaction, and in the last case two separate rotational isomers have been identified. The intermolecular structural parameters and the perturbations of the intramolecular bond lengths and angles are consistent with the trends in the interaction energies. The vibrational spectra have also been examined, and the wavenumber shifts and intensity ratios track with the energetic and structural data. The mechanism of complex formation in each case is donation of a lone pair of electrons on the N or O atoms into the π* orbital of BF3, with back donation in the case of the complex bound through the nitrogen atom from a lone pair on one of the F atoms of BF3 into the σ*(OH) orbital of HONO. The total amounts of charge transferred vary, in general, with the strengths of interaction, while the charge density topologies and their properties confirm the conclusions derived from the other characteristics discussed. <![CDATA[<b>Synthesis of Triazole-linked 2-Trichloromethylquinazolines and Exploration of Their Efficacy Against <i>P</i> <i>falciparum</i></b>]]> Using 2-trichloromethylquinazoline as scaffold, seven novel triazole-linked compounds have been synthesized using CuAAC chemistry. The in vitro biological activity of four of the compounds on the Plasmodium falciparum chloroquine-sensitive strain NF54 was then determined. The compounds which were tested showed moderate activity with 1.45 /iM as the lowest inhibitory concentration. <![CDATA[<b>A Structural Investigation of the D<sub>2</sub>O Solvated, Acetone Solvated and Nonsolvated 1,4-Diazabicyclo[2.2.2]octane Complexes of the Half Sandwich Moiety [(</b><b>η</b><b><sup>5</sup></b><b>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>Fe]</b>]]> Two new solvates of the dinuclear salt {(η5-C5H5)(CO)2Fe}2(ji-DABCO)](BF4)2 (DABCO = 1,4-diazabicyclo[2.2.2]octane); 1 (D2O solvate) and 2 (acetone solvate), and the mononuclear salt [(η5-C5H5)(CO)2Fe(DABCO)]BF4,3, have been synthesized and structurally characterized. The D2O solvate, 1 forms crystals in the triclinic space group PIMAGEM AQUI, the acetone solvate forms crystals in the monoclinic P21/c space group, while the unsolvated mononuclear salt, 3, forms crystals in the orthorhombic P2(1)2(1)2(1) space group. The respective unit cell parameters are: Compound 1, a = 7.66300(10) Å, b = 12.3133(2) Å, c = 13.9629(2) Å, a = 69.179(1) °, β = 77.114(1) ° and γ = 84.282(1) °; Compound 2, a = 17.3633(3) Å, b = 14.1688(3) Å, c = 11.3542(2) Å, β = 99.344(1) °; Compound 3, a = 8.9936(2) Å, b = 10.8949(3) Å, c = 15.3417(4) Å. The DABCO ligand adopts a twisted conformation with N-C-C-N torsion angles ranging between -21.05(12) to -19.31(12) ° and 15.3(2) -15.7(2) ° in 1 and 2, respectively, whereas in 3, the CH2 groups of each NCH2CH2N moiety are almost eclipsed, the torsion angles ranging from -2.89(18) to -1.50(16) °. <![CDATA[<b>One-Pot, Simple and Efficient Synthesis of Triaryl-1<i>H</i>-imidazoles by KMnO<sub>4</sub>/CuSO<sub>4</sub></b>]]> 2,4,5-Triarylimidazoles have been obtained in excellent yields by the one-pot three-component condensation of bis-aryl a-hydroxyketones, aromatic aldehydes and ammonium acetate by the action of inexpensive, readily available and nontoxic KMnO4/CuSO4 under mild reaction conditions. The present method is simple, efficient, cost-effective and eco-friendly. <![CDATA[<b>Synthesis and Antimicrobial Activities of Some New Pyrazoles, Oxadiazoles and Isoxazole Bearing Benzofuran Moiety</b>]]> The synthesis of novel derivatives of pyrazole-3-carboxylate (3-5) from methyl 4-(benzofuran-2-yl)-2,4-dioxobutanoate (1)is reported. Synthesis of substituted 1,3,4-oxadiazoles (7-11) and 5-amino pyrazole-4-carboxylate (12) derivatives starting from the 5-(benzofuran-2-yl)-1-phenyl-1H-pyrazole-3-carbohydrazide (6) are also described. Twelve new compounds were synthesized and their identities have been established on the basis of elemental and spectroscopic analysis such as IR, ¹H NMR, 13C NMR, Mass Spectra. The compounds were also screened for their antibacterial and antifungal activities against Gram-positive, Gram-negative bacteria and a fungus. <![CDATA[<b>Poly (Ethylene Glycol)-Bound Sulphonic Acid as a Novel Catalyst for Synthesis of Benzoxazoles</b>]]> A highly efficient, simple and rapid method for the preparation of various 2-aminobenzoxazoles and other benzoxazole derivatives using a catalytic amount of poly (ethylene glycol)-bound sulphonic acid (PEG-SO3H) is described. PEG-SO3H is found to be economical and reusable catalyst with low catalytic loading. The percentage yield was found to be satisfactory, experimental set-up and purification of final products is facile and easy. <![CDATA[<b>Inorganic-Organic Hybrids Incorporating a Chiral Cyclic Ammonium Cation</b>]]> In this paper we report the synthesis and the crystal structure of eight inorganic-organic hybrids containing various lead halides as the inorganic motif and a chiral, primary ammonium cation as the organic constituent. The organic cation investigated is (C6H11C*H(CH3)NH3)+ and both the (R) and (S) as well as the racemic (RS) forms were used. Within the structures obtained, three different inorganic motifs are displayed by the lead halide octahedra: 1-D polymeric face-sharing chains of formula ((R)-[C6H5CH(CH3)NH3)PbBr3](4) and [((S)-C6H5CH(CH3)NH3)PbBr3](5); 1-D polymeric corner-sharing ribbons based on the terminated-K2NiF4 type structure of formula ((R)-[C6H5CH(CH3)NH3)8Pb8I14](1) and [((S)-C6H5CH(CH3)NH3)8Pb8I14] (2); and 2-D corner-sharing layers based on the K2NiF4 perovskite structure type of formula [((RS)-C6H5CH(CH3)NH3)2PbBr4] (3), [((RS)C5H5CH(CH3)NH3)2PbCl4] (6), (R)-[C6H5CH(CH3)NH3)2PbCl4] (7) and [((S)-C6H5CH(CH3)NH3)2PbCl4] (8). <![CDATA[<b>Synthesis, Characterization and Antibacterial Activity of New 1,2- and 1,4-Bis(<i>N' -</i>Substituted Thioureido)benzene Derivatives</b>]]> Synthesis of two series of 1,2- and 1,4-bis(thioureido)benzene derivatives was accomplished by the treatment of corresponding alkanoyl/aroyl chlorides with potassium thiocyanate in dry acetone to afford the respective isothiocyanates as intermediates. The latter were treated in situ with 1,2- and 1,4-diaminobenzene, respectively, to afford the title compounds in high yields. A total of sixteen new compounds are reported herein. The structures of the products were confirmed by spectroscopic techniques (IR, ¹H and 13C NMR, mass spectrometry), elemental analysis and in case of 1d, by X-ray diffraction technique. All the synthesized compounds were also subjected to antibacterial bioevaluation against ten different Gram-positive and Gram-negative bacterial strains using levofloxacin as the standard drug and were shown to possess promising activities. <![CDATA[<b>Oxidized Single-Walled Carbon Nanotubes (SWCNs-COOH) as a New Catalyst for the Protection of Carbonyl Groups as Hydrazones</b>]]> Nano-materials are considered as suitable heterogeneous catalysts for many organic reactions. Herein oxidized carbon nanotube (SWCNTs-COOH) has been reported as a heterogeneous catalyst, for protection of carbonyl groups as hydrazones in EtOH at 80 °C. The reactions proceed smoothly with good to excellent yields, and the SWCNTs-COOH used can be recycled. <![CDATA[<b>Cesium salts of phosphotungstic acid: Comparison of surface acidity, leaching stability and catalytic activity for the synthesis of </b><b>β</b><b>-ketoenol ethers</b>]]> Catalytic activity of Cs xH3-xPW12O40 catalysts were investigated in the synthesis of β-ketoenol ethers. It was found that activity; acidity, solubility and consequently, recoverability of these catalysts are related to cesium content. A series of β-ketoenol ether derivatives were synthesized by using Cs25H0.5PW12O40 catalyst in high to excellent yields. This catalyst showed highest surface acidity and lowest solubility in reaction media in comparison with the other cesium content salts. <![CDATA[<b><sup>1</sup></b><b>H NMR-based kinetic-mechanistic study of the intramolecular trans-esterification of 2-<i>exo</i>-3-<i>exo</i>-dihydroxybornane monoacrylate esters</b>]]> A ¹H NMR study of the acid-catalyzed, intramolecular trans-esterification between isomeric 2-exo-3-exo-dihydroxybornane monoacrylate esters has afforded insights into the reaction mechanism and permitted the determination of kinetic and thermodynamic parameters for the pseudo-first-order processes.