Scielo RSS <![CDATA[South African Journal of Chemistry]]> http://www.scielo.org.za/rss.php?pid=0379-435020140001&lang=pt vol. 67 num. lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>The inhibiting or accelerating effect of different surfactants on electroreduction of Zn<sup>2+</sup></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100001&lng=pt&nrm=iso&tlng=pt The course of differential capacity curves of the electric double layer at the mercury electrode/surfactant solution interface was described for three different surfactants from different groups. Using square-wave voltammetry (SWV) it was found that the surfactants had a varying effect on the kinetics of electroreduction of Zn2+ ions. Simple relationships were presented between SWV peaks and the course of differential capacity curves in the presence of surfactants as compared with the curve of differential capacity for the basic electrolyte. <![CDATA[<b>Synthesis of MoS<sub>2</sub> inorganic fullerene-like nanoparticles by a chemical vapour deposition method</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100002&lng=pt&nrm=iso&tlng=pt MoS2 nanoparticles with fullerene-like structure (IF-MoS2) were successfully obtained at heating temperature higher than 840 °Cby a chemical vapour deposition method using MoO3 and sulfur powders as raw materials. The synthesized samples were characterized by XRD, SEM, TEM, EDX and Raman spectrometry, respectively. The reaction temperature has important influences on composition and morphology of the products, and pure IF-MoS2 nanoparticles can be obtained only in the narrow temperature range of 840-870 °C. Diffraction peak (002) of IF-MoS2 nanoparticles moves to small angle compared to that of 2H-MoS2, indicating that the adjacent lattice spacing along the c-axis of IF-MoS2 nanoparticles is about 2 % larger than that of layered 2H-MoS2. The peaks at 155 cm-1, 349.8 cm-1 and 281.7 cm-1 in the Raman spectrum of bulk and layered MoS2 are absent, which is attributed to MoS2 layer folding or curling along Γ-M in Brillouin zone to form fullerene-like polyhedra and nanotubes. In addition, a gradual formation mechanism of IF-MoS2 nanoparticles was discussed in detail. <![CDATA[<b>Rating of sweetness by molar refractivity and ionization potential</b>: <b>QSAR study of sucrose and guanidine derivatives</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100003&lng=pt&nrm=iso&tlng=pt A quantitative structure activity relationship study of 31 sucrose derivatives and 30 guanidine derivatives has been undertaken. Their sweetness values, relative to sucrose (RS), have been taken from literature. The study has been made with the help of CAChe Pro software by using eight descriptors, viz. electron affinity, ionization potential, electrophilicity index, total energy, heat of formation, steric energy, molar refractivity and solvent accessible surface area. Multi-linear regression (MLR) analysis has been performed with different combinations of descriptors and the quality of regression has been adjudged by the correlation coefficient, cross-validation coefficient and other statistical parameters like the standard error, standard error of the estimate, degrees of freedom, etc. The study indicates that ionization potential appears an important descriptor for sucrose derivatives, whereas molar refractivity appears an important descriptor for guanidine derivatives. The ionization potential alone and in combination with the electrophilicity index, molar refractivity and solvent accessibility surface area provide dependable QSAR models for sucrose derivatives. Molar refractivity alone and in combination with solvent accessibility surface area, ionization potential and heat of formation provide dependable QSAR models for guanidine derivatives. The predicted sweetness values obtained by these QSAR models are close to observed sweetness. <![CDATA[<b>Nano-TiCl<sub>4</sub>.SiO<sub>2</sub></b>: <b>a versatile and efficient catalyst for synthesis of dihydropyrimidones <i>via</i> Biginelli condensation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100004&lng=pt&nrm=iso&tlng=pt Nano-TiCl4.SiO2 has been found to be an extremely efficient catalyst for the preparation of 3,4-dihydropyrimidinones/thiones via three-component reactions of an aldehyde, β-ketoester or β-diketone and urea or thiourea under mild conditions. Nano-TiCl4.SiO2 as a solid Lewis acid has been synthesized by reaction of nano-SiO2 and TiCl4. The structural characterization of this acid has been studied by FT-IR (ATR), XRD, SEM and TEM. This process was simple and environmentally benign with high to excellent yields. Furthermore, the catalyst could be recovered conveniently and reused for at least three times. <![CDATA[<b>A simple and efficient synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[<i>a</i>]xanthen-11-ones by ZnO nanoparticles catalyzed three component coupling reaction of aldehydes, 2-naphthol and dimedone</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100005&lng=pt&nrm=iso&tlng=pt Highly effective zinc oxide nanoparticles catalyzed solvent-free synthesis of some tetrahydrobenzo[a]xanthen-11-one derivatives via one-pot multi-component reaction of aldehydes, 2-naphthol and dimedone. The present approach creates a variety of biologically active heterocyclic compounds in excellent yields and short reaction times. Four new compounds are reported. The salient features of the ZnO nanoparticles are: easy preparation, cost-effective, high stability, low loading and reusability of the catalyst. The prepared zinc oxide nanoparticles were fully characterized by EDX, XRD, SEM, IR and TEM analysis. <![CDATA[<b>Beef-derived mesoporous carbon as highly efficient support for PtRulr electrocatalysts and their high activity for CO and methanol oxidation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100006&lng=pt&nrm=iso&tlng=pt In this work, a low-cost and nitrogen-containing carbon with mesoporous pores and high surface area was synthesized by carbonizing a natural biomass precursor, i.e. beef. It is found that the prepared material has excellent textural properties such as high specific surface areas and large pore diameters. TEM images showed that the PtRuIr nanoparticles were well dispersed on the surface of carbonized beef (C-Beef). PtRuIr/C-Beef was highly active for methanol electro-oxidation. PtRuIr/C-Beef showed superior catalytic activity to PtRuIr/C, i.e. lower onset potential and higher oxidation current density. Cyclic voltammograms of CO electro-oxidation showed that PtRuIr/C-Beef catalyst was kinetically more active for CO electro-oxidation than PtRuIr deposited on conventional carbon support. The highly porous structure and low cost of carbonized beef can be widely used as support for highly dispersed metal nanoparticles to increase their electrochemical performance as electrocatalysts. <![CDATA[<b>Students' conceptions about the sub-microscopic approach to explanations in chemistry throughout their BSc degree course</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100007&lng=pt&nrm=iso&tlng=pt The main objective of this study was to test chemistry students' competence, throughout the entire BSc course at North-West University (Mafikeng Campus), in the use of the important and widely applicable strategy of explaining the facts, principles and laws of chemistry in terms of the properties of the constituent sub-microscopic particles. Seventeen questions were used for systematically testing all basic aspects of chemistry. The aspects tested included the following: the types of particles present and their properties in various types of matter (e.g. metals, non-metals, ionic compounds, covalent compounds, mixtures, gases, liquids, solids, solutions); the changes in the nature, arrangement and properties of the particles during both physical and chemical changes; the explanation of physical and chemical properties of substances in terms of the properties of the constituent particles. Student performance was consistently bad and it did not improve as they progressed from year to year in their BSc course. More than half of them (average performance in all questions) had difficulty in answering the questions. Analysis of students' answers suggested that most students' difficulties were due to their not identifying clearly the problem that had to be solved and their not using the relevant principles and reasoning to solve the problems. Instead, most students tried to solve problems by recalling knowledge, procedures and solutions they had learnt. The lack of improvement from year to year indicates the need for continuously training students in the sub-microscopic approach to interpretations and explanations throughout the BSc course, and not just in the first year as is done presently. <![CDATA[<b>Synthesis, characterization and antimicrobial activity of copper(II) complexes of some ortho-substituted aniline Schiff bases; crystal structure of bis(2-methoxy-6-imino)methylphenol copper(II) complex</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100008&lng=pt&nrm=iso&tlng=pt This study presents the synthesis, characterization and antimicrobial activity of copper(II) complexes of some ortho-substituted aniline Schiff bases (L¹-L8). The Schiff bases and their respective copper(II) complexes were characterized by a combination of elemental analysis, infrared and UV/Visible studies. The structures of the ligands were also confirmed from ¹H- and 13C-NMR spectral data. The infrared and electronic transition studies showed that the ligands are bidentate coordinating via the imine nitrogen and the phenolic oxygen atoms in a planar configuration. Introduction of aqueous ammonia to the ethanolic solution of L³/L4 and Cu(OAc)2.H2O aliquot yielded an ammonia-based complex due to the hydrolysis of the imine bond. The crystal structure of the resulting complex indicated a square planar geometry. The copper(II) ion crystallizes in the monoclinic system with a space group of P21/c having a = 10.9309, b = 4.85600, c = 17.7030, α = γ = 90 ° and β = 119.658 °. The geometry is slightly distorted from planarity with O1-Cu1-N1 bond angles of 92.19 ° and 87.8 °. The Schiff base ligands and their respective copper(II) complexes were screened for their in vitro antibacterial and antifungal activity against Escherichia coli ATCC® 8739™*, Staphylococcus aureus subsp. aureus ATCC® 6538™*, Bacillus subtilis subsp. spizizenii ATCC® 6633™* and Candida albicans ATCC® 2091™*. The o-vanillin-based ligands exhibited higher activity than the salicylaldehyde derivatives which were virtually non-active against the tested organisms. <![CDATA[<b>Reaction of hydrazine hydrate with oxalic acid: synthesis and crystal structure of dihydrazinium oxalate</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100009&lng=pt&nrm=iso&tlng=pt The reaction of oxalic acid with hydrazine hydrate (in appropriate mole ratio) forms the dihydrazinium oxalate under specific experimental condition. The title compound is a molecular salt containing two discrete hydrazinium cations and an oxalate anion. The oxalate anion is perfectly planar and there is a crystallographic centre of symmetry in the middle of the C-C bond. The C-O bond distances are almost equal indicating the presence of resonance in the oxalate ion. The crystal packing is stabilized by intermolecular N-H · O and N-H · N hydrogen bonds. The oxalate ions are linked together end to end through hydrogen bonds (via N2H5+ ions) and run parallel to the [101] direction. It is interesting to note that each oxalate group in the structure is surrounded by six hydrazinium ions through hydrogen bonding. Similarly, each hydrazinium ion is surrounded by three oxalate and one hydrazinium ion. <![CDATA[<b>Monitoring of Herbicides in Aquatic Environments using the Bubble-in-Drop Single Drop Micro-Extraction (BID-SDME) Method</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100010&lng=pt&nrm=iso&tlng=pt Environmental monitoring can be a costly exercise for the legislative bodies to enforce regulatory mechanisms since most herbicides are hazardous in the environment. This study reports on the potential application of a cheaper sample preparation method termed 'bubble-in-drop' single drop micro-extraction (BID-SDME) method for monitoring metolachlor and atrazine herbicides used in maize farming in South Africa. The method demonstrated excellent applicability for aqueous samples obtained from streams impacted by farming activities where concentrations ranging from 25 to 50 ng mL-1 were determined. The detection limits of the method were in the range of 0.047 to 0.061 ng mL-1, which are considerably lower than those prescribed by the EPA Method 507. Recovery studies using 10 ng mL-1 solutions demonstrate excellent recoveries ranging from 94 to 108 % for respective herbicides. However, the challenge remains the detection of the breakdown products since only the parent herbicides were detected in this study. <![CDATA[<b>Selective Adsorption of Tetrahydropalmatine by a Molecularly Imprinted Polymer with Modified Rosin Cross-linker</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100011&lng=pt&nrm=iso&tlng=pt A molecularly imprinted polymer (MIP) containing a phenanthrene skeleton was prepared by suspension polymerization with ethylene glycol maleic rosinate acrylate (EGMRA) as the cross-linker, tetrahydropalmatine (THP) as the template, and methacrylic acid as the functional monomer. A non-imprinted polymer (NIP) was similarly prepared and treated, but in the absence of THP The MIP and NIP were characterized by scanning electron microscopy and nitrogen sorption and thermal gravimetric analyses. The time taken by the MIP to reach THP (C0 = 2.8 mmol L¹) adsorption equilibrium was 4.5 h, and the recognition factor of the MIP for THP was 2.09. The change in microcalorimetric heat flow during adsorption revealed that the MIP had a higher affinity to THP compared with NIP. Selective adsorption experiments demonstrated the high affinity and THP selectivity of the MIP. <![CDATA[<b>Synthesis of Novel Piperazine-linked Anthranilic Acids as Potential Small Molecule Kinase Inhibitors</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100012&lng=pt&nrm=iso&tlng=pt Substituted anthranilic acid and piperazines were used as building blocks to prepare two libraries of compounds, with the aim being that they would exhibit biochemical activity as small molecule kinase inhibitors. The synthesized anthranilamide-piperazine compounds were subsequently tested against a panel of kinases including EGFR, Abl, Akt and Aurora B. <![CDATA[<b>Conformational Comparison of Cyclic </b><b>α</b><b><sub>3</sub></b><b>β</b><b> Tetrapeptide vs. </b><b>α</b><b><sub>3</sub></b><b>β</b><b> Pentapeptide</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100013&lng=pt&nrm=iso&tlng=pt The γ-turn inducing sugar β-amino acid plays an important role in the formation of well-defined secondary structures of cyclic tetra- and pentapeptide. Two tetra- and one novel pentapeptide were synthesized from a sugar β-amino acid and the conformations of the compounds were established by NMR spectroscopy (EASY-ROESY) and compared with CD spectroscopic data. Although the γ-turn conformation was dominant for both tetra- and pentapeptide according to NMR spectroscopic analysis in DMSO, the pentapeptide exhibited the presence of a second conformation. CD spectroscopic results in methanol showed that the tetrapeptides have a γ-turn conformation, while the pentapeptide has a random structure. <![CDATA[<b>Synthesis and Spectroscopic, Thermal and Crystal Structure Studies of Hydrazinium Hydrogensuccinate</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100014&lng=pt&nrm=iso&tlng=pt The mono-hydrazinium salt of succinic acid (hydrazinium hydrogensuccinate salt) was prepared by reacting hydrazine hydrate and succinic acid. Its spectral, thermal and structural properties have been determined. The salt, N2H5+.C4H5O4-, is a molecular salt containing discrete hydrazinium cations and hydrogen succinate anions. The crystal packing consists of infinite chains of anions and cations that are alternatively linked through O-H···N and bifurcated N-H···O bonds and this chain is connected to adjacent antiparallel chains by N-H···O hydrogen bonding. The adjacent chains are cross linked by N-H···O bonds from the donor N2H5+ ions, thus forming a three-dimensional network. The salt undergoes melting followed by decomposition to give gaseous products. <![CDATA[<b>Diorganotin(IV) Complexes with Methionine Methyl Ester. Equilibria and Displacement by DNA Constituents</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100015&lng=pt&nrm=iso&tlng=pt The coordination of methionine methyl ester with dimethyltin(IV) (DMT), dibutyltin(IV) (DBT) and diphenyltin(IV) (DPT) was investigated at 25 °C and 0.1 mol dm-3 ionic strength in water for dimethyltin(IV) and in 50 % dioxane-water mixture for dibutyltin(IV) and diphenyltin(IV). Methionine methyl ester forms 1:1 and 1:2 complexes with diorganotin(IV). The corresponding formation constants were calculated by using the non-linear least-squares program MINIQUAD-75. The concentration distribution of the various complex species was evaluated as a function of pH. The displacement of coordinated methionine methyl ester with some DNA constituents was calculated based on equilibrium aspects. <![CDATA[<b>Simultaneous Determination of Bisphenol A and Bisphenol S in Environmental Water using Ratio Derivative Ultraviolet Spectrometry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100016&lng=pt&nrm=iso&tlng=pt A simplified method based on ratio derivative ultraviolet spectrometry for simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS) in environmental water is presented. The method provides a direct analysis of the samples without tedious sample preparation. In this method, the overlapping spectra of BPA and BPS were well resolved using the first derivative (Δλ = 1 nm) of the ratio of their absorption spectra. Measurements of absorbance were performed at wavelengths of 229.5 nm and 245.5 nm for BPA and BPS, respectively, using the ratio derivative spectrum method. Beer's law was followed in the concentration range of 8.8 X 10-7-2.2 X 10-4 mol dm-3 for BPA and 1.4 X 10-6-1.0 X 10-4 mol dm-3 for BPS. The limits of detection were 3.5 X -7 mol dm-3 for BPA and 4.4 X 10 7 mol dm ³ for BPS. Their 5:1 to 1:5 mixtures were resolved with recoveries between 90.5 % and 100.9 % for BPA and between 93.8 % and 101.1 % for BPS. The method was satisfactorily applied to the simultaneous determination of BPA and BPS in environmental water samples. <![CDATA[<b>A New Kinetic Spectrophotometric Method for Total Polyphenols Determination in White Wines</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100017&lng=pt&nrm=iso&tlng=pt This paper describes a new, simple and sensitive catalytic kinetic spectrophotometric method for the determination of total polyphenols in white wines. The method was based on the catalytic effect of Cu(II) on the oxidation of phenolic compounds by H2O2 in acid media. The reaction was followed spectrophotometrically by measuring the increase in absorbance of oxidation products at 420 nm. Under optimal experimental conditions, a differential variation of the tangent method was used to obtain a calibration curve over the range of 23.01-194.11 μg mL-1 of phenols. The calculated detection limit (3.3S0/b) was 6.77 μg mL-1 for ten replicate measurements of blank signal. The relative standard deviations for five replicate determinations on 70.0, and 170.0 μg mL-1 of galic acid were 2.49 and 1.79 %, respectively. The proposed method was successfully applied for the determination of total polyphenols in white wine samples and the results were in excellent agreement with the Folin-Ciocalteau method. <![CDATA[<b>Silica-Supported Yttrium Nitrate Hexahydrate as a Heterogeneous Catalyst for the Synthesis of 2-Amino-4<i>H</i>-Chromenes in Water</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100018&lng=pt&nrm=iso&tlng=pt Silica-supported yttrium nitrate hexahydrate (Y(NO3)3.6H2O/SiO2) has been found to be an efficient and reusable catalyst for the synthesis of 2-amino-4H-chromenes via a one-pot aqueous three-component reaction between arylaldehydes, malononitrile and ß-naphthol in high yields. This method has many appealing attributes such as excellent yields, short reactions time, reusability of the catalyst and simple work-up procedure. <![CDATA[<b>Exploration of the Potential of using a Virtual Laboratory for Chemistry Teaching at Secondary School Level in Lesotho</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100019&lng=pt&nrm=iso&tlng=pt With the ever-increasing economic challenges facing education in Lesotho and indeed the world at large, there is a need for innovative solutions to support academic programmes without compromising quality. The use of computer simulations and video demonstrations is increasingly finding use globally in order to respond to economic challenges and purportedly to improve understanding of abstract phenomena. This manuscript presents the views of the chemistry teachers and students registered at the National University of Lesotho (NUL) towards the development of a Virtual Laboratory (VL) where the experiments in the secondary school chemistry syllabus, will be video-recorded and distributed to schools. The results demonstrated a need for VL since only 4 % of the respondents indicated having performed more than 10 experiments with reasons ranging from poorly equipped laboratories (66 %) to no laboratories (6 %) for fewer to no experiments having been performed. This venture is generally accepted (96 % of 166 respondents) with only a minority stating it can never replace physical laboratory. Distribution of the VL would require innovative means since internetaccessibility seems a challenge for most schools with accessibility of only 35 %. <![CDATA[<b>Determination of Carboxylic Acids and Water-soluble Inorganic Ions by Ion Chromatography in Atmospheric Aerosols from Tanzania</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100020&lng=pt&nrm=iso&tlng=pt Atmospheric aerosol samples of PM2,5 and PM10 were collected in April-May 2011 from a rural site in Tanzania and analyzed for water-soluble inorganic ions and low molecular weight carboxylic acids using ion chromatography. PM2,5 and PM10 low-volume samplers with quartz fibre filters were deployed and aerosol collections on a 24 h basis were made for each sampler. All samples were analyzed for carboxylates and inorganic ions by using ion chromatography. The results showed that mean mass concentration of PM2,5 and PM10 were 13 ± 3.5 µg m-3 and 16 ± 2.3 µg m-3, respectively. Mean concentrations of the total carboxylates were 23.7 ± 6.5 ng m-3 in PM2.5 and 36.4 ± 12 ng m-3 in PM10 whereas total water-soluble inorganic ions were 448 ± 88 ng m-3 and 646 ± 214 ng m-3, respectively. Oxalate and malonate in PM25 and acetate in PM10 were most abundant carboxylates accounting for 64 % and 62 % of total acids, respectively. Mg2+ was most important cation in PM25 and PM10 accounting for 44 % and 24 % of total water-soluble ions, respectively, whereas SO4(2-) was the main anionic component accounting for 23 % of total ions species in PM25 and 37 % in PM10. Using source indicators, we found photochemical activities, biogenic and biomass burning could possibly be important source types for aerosols in Tanzania. <![CDATA[<b>Determination of Triclosan and Ketoprofen in River Water and Wastewater by Solid Phase Extraction and High Performance Liquid Chromatography</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100021&lng=pt&nrm=iso&tlng=pt This paper describes a simple, sensitive and rapid method for the determination of triclosan and ketoprofen in wastewater influent, effluent and river water. The method involves solid phase extraction (SPE) of target compounds using Oasis HLB sorbent. Several extraction parameters such as sample pH, sample volume, SPE cartridge and SPE elution solvent were optimized. The pH of the collected samples was adjusted to 5.5, and then 100 mL of the sample was loaded into an Oasis HLB cartridge. Methanol was used to elute the retained compounds. The eluted compounds were analyzed using reversed-phase high performance liquid chromatography with photo diode array detection (HPLC-PDA). The method was validated by spiking ultra-pure water and wastewater with different concentrations of both compounds ranging from 5 ju,g L-1 to 1000ju,g L-1. Recoveries were in the range of 73 % to 104 %, and % RSD ranged from 8%to15%. The method gave good detection limits of 0.01 and 0.08 ju,g L-1 for triclosan and ketoprofen, respectively. Traces of both compounds were detected in all wastewater (influent and effluent) samples at a range of 1.2 to 9.0 ju,g L-1 and in some river water samples. <![CDATA[<b>Three-component Synthesis of Electron-poor Alkenes using Isatin Derivatives, Acetylenic Esters, Triphenylphosphine and Theoretical Study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100022&lng=pt&nrm=iso&tlng=pt Synthesis of electron-poor alkenes has been reported by 1,2-proton shift and elimination of triphenyl phosphine from phosphorus ylide in good to high yields. The structures of six novel products were deduced from their IR, ¹H NMR, and 13C NMR spectra. The B3LYP/HF calculations for computation of ¹H and 13C NMR chemical shifts have been carried out for the compounds with the 6-31G* basis set utilizing the GIAO approach. In addition, theoretical configurations of the title compound were studied in terms of the combined analysis of the HOMO-LUMO energy gap, NBO analysis, thermodynamic parameters and molecular electrostatic potential (MEP). Also ionization potential (I), electron affinity (A), chemical hardness (η), electronic chemical potential (μ) and electrophilicity (ω) of the title molecule are reported. All calculations were performed using B3LYP method with the 6-31G* basis set. <![CDATA[<b>Quininium Malates: partial chiral discrimination <i>via</i> diastereomeric salt formation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100023&lng=pt&nrm=iso&tlng=pt Quinine was employed as a resolving agent for racemic malic acid. The resultant product was a quininium salt containing 75 % of the D-malate anion. Quinine was also crystallized with pure L- and D-malic acids and the structures of the resulting diastereomeric salts were elucidated. The crystal packings were analyzed in terms of their non-bonded interactions and the conformation of the quinine, which was compared with other quinine structures recorded in the Cambridge Structural Database. The results indicate that the mechanism of enantiomeric resolution is reliant upon hydrogen bonded interactions. <![CDATA[<b>An Efficient and Rapid Access to the Synthesis of Tetrahydrochromeno[4,3-b]chromene-6,8-dione Derivatives by Magnesium Perchlorate</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100024&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>A Serendipitous Formation of a Cysteine-bridged Disaccharide</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100025&lng=pt&nrm=iso&tlng=pt N-acetyl-L-cysteine bearing free carboxylic acid and sulfhydryl groups was glycosylated with 1,2,3,4,6-Penta-O-acetyl-ß-D-glucopyranoside in the presence of SnCl4 as a promoter to give the S-glycosylated cysteine in 64 % yield. However, when excess donor was used, a previously unreported cysteine-bridged disaccharide was isolated in 54 % yield. The acetamido group on cysteine, which lowers the pKa of the carboxylic acid group of the amino acid, plays no role in the formation of the bridged disaccharide since 3-mercaptopropionic acid reacts in a similar manner to give the 3-mercaptopropionic acid-bridged disaccharide in 52 % yield. <![CDATA[<b>Analysis of Volatile Compounds in <i>Khadi </i>(an Unrecorded Alcohol Beverage) from Botswana by Gas Chromatography-Flame Ionization Detection (GC-FID)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100026&lng=pt&nrm=iso&tlng=pt Chemical analysis of volatile compounds from khadi, an unrecorded alcoholic beverage from Botswana, was carried out using gas chromatography-flame ionization detection (GC-FID). Ten samples of khadi from two different locations were analyzed. All samples had pH values in the range of 2.87-3.16. Overall the samples contained ethanol, higher alcohols and esters. Ethanol was observed to be the dominant volatile compound with concentrations ranging from 1.66-5.71 % vol. Other volatiles determined were 2-methyl-1-propanol (9.12-29.0 mg L-1) and 2/3-methyl-1-butanol (14.5-124.7 mg L-1), ethyl lactate (27.4-110.9 mg L-1) and ethyl acetate (28.3-48.5 mg L-1). <![CDATA[<b>Rhenium(V) complexes containing mono- and tridentate imido ligands: crystal structures, spectroscopic results and DFT optimization</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100027&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Inhibitory of newly synthesized 3-BrPhOXTs on corrosion of stainless steel in acidic medium</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100028&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>An efficient green synthesis of 3-Amino-1<i>H</i>-chromenes catalyzed by ZnO Nanoparticles thin-film</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100029&lng=pt&nrm=iso&tlng=pt A very simple and environmentally benign approach for the synthesis of 3-amino-1ff-chromenes is described using ZnO nanoparticles thin-film as an efficient heterogeneous catalyst in green media, namely water. The mild reaction conditions, reusability of the catalyst, easy work-up and high yields of products make the present protocol sustainable and advantageous compared to conventional methods. <![CDATA[<b>Thermodynamic study of inclusion interactions between gemini surfactants and ß-cyclodextrin</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100030&lng=pt&nrm=iso&tlng=pt The inclusion complexes of gemini surfactants, (CnN)2C1(2) (where n = 12,14), and p-cyclodextrin (p-CD) in aqueous solutions were investigated by an isothermal titration calorimetric method and ¹H NMR spectroscopy at 293.15 K. The stability constants, stoichiometry, formation enthalpies, entropies and Gibbs energies for the complexes in aqueous solution have been derived from the calorimetric data. p-CD in aqueous (C12N)2Cl2/(C14N)2Cl2 solutions forms 2:1 mole ratio host-guest complexes. The large values of the stability constants indicate that these complexes are stable in the aqueous solutions. The negative Gibbs energy changes indicate that formation of the host-guest complexes is generally a spontaneous process. Both the formation enthalpy and formation entropy evidently decrease as the number of methylenes in each of the hydrophobic tails increase. The thermodynamic parameters are discussed in the light of the different structures of the host and guest molecules. Chemical shift data of protons in the CD molecule, induced by the formation of the complexes have been determined by ¹H NMR spectroscopy. <![CDATA[<b>Interaction of 3-Hydroxypicolinamide with Tb<sup>III</sup> and its sensitizing effect on terbium luminescence as a function of pH and medium</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100031&lng=pt&nrm=iso&tlng=pt Coordination behaviour of 3-hydroxypicolinamide (HPA) towards TbIII is studied in aqueous and micellar media. The complex formed exists as ML2 species in which HPA behaves as an O,O,N,N-chelating ligand. The solid complex is isolated from aqueous medium and characterized employing elemental analysis, TG/DTA, magnetic, IR, ESR and mass spectral data. Stability constant and other accompanying thermodynamic parameters of the Tb(III) complex have been determined pHmetrically. The complexation reaction is spontaneous and exothermic. Effect of micelles and pH on the luminescence of Tb(III) were also studied. The emission peaks of Tb m are highly sensitized on complexation with HPA and the optimum luminescence efficiency is obtained in slightly acidic to neutral solutions (pH 6-8). The complex decays biexponentially and the presence of ethanol and surfactants causes a large increase in the luminescence intensity protecting the complex from radiationless deactivation processes. <![CDATA[<b>Development of a reliable method for the spectrophotometric Determination of Palladium(II) with o-Methoxyphenyl Thiourea: Separation of palladium from associated metal ions</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100032&lng=pt&nrm=iso&tlng=pt A simple and sensitive method is described for the solvent extraction and spectrophotometric determination of palladium(II) using low concentrations of o-methoxyphenyl thiourea (OMePT). Trace concentrations of palladium(II) were quantitatively extracted when equilibrated with OMePT in chloroform at 1.0 mol L-1 hydrochloric acid media for 10 s. The absorbance of a yellow coloured palladium(II)-OMePT complex was measured at 325 nm. The palladium(II)-OMePT complex was stable for more than 72 h. The composition of extracting species was 1:1, determined by mole ratio, Job's continuous variation method and it was confirmed by a log-log plot. Beer's law was obeyed up to 15.0 mL-1. The molar absorptivity and Sandell's sensitivity were 3.38 X 10³ L mol-1 cm-1 and 0.031 cm-2, respectively. The method was free from a large number of interferences from cations and anions. The method was applied for separation of palladium(II) from multi-component mixtures and synthetic mixtures corresponding to alloy. <![CDATA[<b>Synthesis, crystal structure and anti-ischaemic activity of (E)-1-{4-[Bis(4-methoxy-phenyl)methyl]piperazin-1-yl}-3-(4-chlorophenyl)-prop-2-en-1-one</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100033&lng=pt&nrm=iso&tlng=pt The title compound (E)-1-{4-[bis(4-methoxyphenyl)methyl]piperazin-1-yl}-3-(4-chloro- phenyl)prop-2-en-1-one (C28H29ClN2O3, Mr = 476.98) (5) was synthesized and studied by the single crystal X-ray diffraction method. Its structure was confirmed by ¹H NMR, 13C NMR, HRMS and X-ray single crystal structure determination. Compound 5 crystallized in the monoclinic system, space group P2(1)/c with a = 10.392(2), b = 7.9180(16), c = 30.474(6) Å, β = 97.78(3) °, V = 2484.4(9) ų,Z = 4, Dc = 1.275 g cm-3, F(000) = 1008, μ = 0.186 mm-1,MoKa radiation (λ = 0.71073 Å), R = 0.0692 and wR = 0.1469 for 2046 observed reflections with I 2σ(I). The title compound was screened for the anti-ischaemic activity in vivo. The results showed that compound 5 significantly prolonged the survival time of mice subjected to acute cerebral ischaemia at all doses tested and exhibited potent neuroprotective activity. <![CDATA[<b>Speciation and persistence of dimethoate in the aquatic environment: characterization in terms of a rate model that takes into account hydrolysis, photolysis, microbial degradation and adsorption of the pesticide by colloidal and sediment particles</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100034&lng=pt&nrm=iso&tlng=pt The kinetics of the degradation of dimethoate in an aquatic microcosm ecosystem, and a distilled water control, charged with the pesticide was studied over a period of 90 days. The concentration of dimethoate was monitored in the distilled water control, as well as the water phase and sediment phase of the experiment. The loss of the pesticide after a given time period was calculated and plotted as a function of time. Biphasic linear rates of dimethoate degradation were observed for both the water phase (3.12 and 0.358 mL -1 day-1, respectively) and the sediment phase (108 and 1.03 g-1 day-1, respectively) in the experimental microcosm, as well as the distilled water control (0.694 and 0.0388 mL -1 day-1, respectively). The linear rates of degradation in distilled water are attributed to hydrolysis and photochemical degradation. The biphasic linear rates of degradation in the experimental microcosm are attributed to microbial degradation of pesticide adsorbed by sediment or colloidal particles, and an enzymatic kinetics model is presented to account for the observed kinetics. The factors that affect the rates of degradation, possible dimethoate pollution remediation strategies, and characterization of the different speciation forms in terms of rates of degradation and apparent adsorption/desorption thermodynamic properties, are discussed. <![CDATA[<b>James Moir (1874-1929) Pioneering Chemical Analyst in South Africa in the Early 1900s</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100035&lng=pt&nrm=iso&tlng=pt James Moir, a pioneering chemist in South Africa, played a leading role in the SA Chemical Institute. He was an excellent organic chemist, who published widely on the relationship between the colour of an organic substance and its chemical structure. In addition to this, he worked as an analyst in the Government Chemical Laboratories in Johannesburg, where he was exposed to a wide variety of chemical analyses. He developed many new methods of analysis and improved others, which he published in the official journal of the Chemical Institute. This article traces his chemical analysis research work as gleaned from the pages of this journal. It deals with coal analysis, where he developed a simple formula to predict the calorific value, determination of nitrous fumes in air with special reference to fuse-igniters, improving the structure of methyl orange as an indicator, analysis of metals such as Cu, Co, As and Cr, and cyanide analysis. Furthermore, the article discusses his sensitive test for phenol and gives a case study where he did some chemical detective work. From all of this, it is apparent that James Moir was a very fine analyst. He is commemorated by Chemistry students for the 'James Moir Medal', awarded annually to the top BSc (Hons) or BTech student at South African universities. <![CDATA[<b>James Moir as Inorganic Chemist</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100036&lng=pt&nrm=iso&tlng=pt James Moir was a pioneering chemist in the early 1900s who played a leading role in various chemical societies in South Africa. Although he was mainly an organic chemist, he also made contributions in the field of inorganic chemistry. His forays in this field deal with gold extraction using the new solvent thiourea, removal of cyanide using ferrous sulphate, and investigations into the 'purple of Cassius'. He was also a theoretical chemist who played a role in the development of atomic theory and made suggestions to help unravel the nature of the atom, the composition of the nucleus and chemical combination. <![CDATA[<b>The Contributions of James Moir to Physical Chemistry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100037&lng=pt&nrm=iso&tlng=pt James Moir was a pioneering chemist in the early 1900s who played a leading role in various chemical societies in South Africa. Although he was mainly an organic chemist, he was a very good all-round chemist, whose analytical and organic activities have already been covered in this j ournal. This article examines his research in physical chemistry, covering the spectral analysis of the ruby and emerald gemstones, a detailed analysis of part of the Fraunhofer lines of the solar spectrum, and an examination of the spectra of cobalt compounds, the permanganate ion, and uranium compounds. Finally, as part of his inorganic and analytical investigations, he also delved into the physical chemistry aspects of solution chemistry, particularly the hydrolysis of the cyanide ion. <![CDATA[<b>James Moir as Organic Chemist</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502014000100038&lng=pt&nrm=iso&tlng=pt James Moir played a leading role in the South African Chemical Institute and was a pioneering organic chemist in South Africa during the early 1900s. He published widely on various organic topics but was especially noted for his work on the relationship between the colour of an organic substance and its chemical structure or constitution. After some initial research work in Scotland and London dealing with amarine and diacetonitrile, he arrived in South Africa in 1902. He first worked on derivatives of diphenol, oxidation products of benzidine, diphenylquinone and other compounds. His immense study of colour covered the years 1916-1929. He put forward theories on colour, which he applied to a whole range of phthaleins and related compounds, in order to see the effect of substitution on the spectrum of the compound. He introduced his numerical solution of colour, by which he could predict the band centre of absorption of many compounds. He applied this to a variety of different dyes and substituted products of phenolphthalein and fluorescein, relating colour to structure. He also studied the factors responsible for organic fluorescence, and doubly-linked diphenylene compounds. Finally he studied the structure of various flower pigments. This article explores his research output in the field of organic chemistry.