Browsing Research articles (Dept of Chemistry) by Title
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Now showing items 59-69 of 69
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Masesane, I.; Steel, P. (Elsevier Ltd; www.elsevier.com/locate/tetlet, June 21, 2004)[more][less]
Abstract: The Diels-Alder adduct of ethyl (E)-3-nitroacrylate and furan provides a versatile template for the stereoselective synthesis of mono and dihydroxylated derivatives of 2-aminocyclohexanecarboxylic acid (ACHC). The hydroxylated ACHC derivatives can be considered to be useful building blocks for B-peptides. URI: http://hdl.handle.net/10311/235 Files in this item: 2
license.txt (1.998Kb)Stereoselective routes to 3-hydroxy.pdf (721.3Kb) -
Chola, J.; Masesane, I.B. (Elsevier Ltd. www.elsevier.com/ locate/tetlet, NaN, 2008)[more][less]
Abstract: Stereoselective syntheses of racemic (1S,2R,3R,4R,5S,6R)- and (1S,2R,3R,4S,5S,6R)-3,4,5,6-tetrahydroxy derivatives of 2-aminocyclohexanecarboxylic acid have been achieved by a stereospecific Diels–Alder reaction between furan and maleic anhydride, a Curtius rearrangement and hydroxylation reactions. URI: http://hdl.handle.net/10311/325 Files in this item: 1
Stereoselective sythesis of 3.pdf (1.100Mb) -
Obuseng, V.; Nareetsile, F.; Kwaambwa, H.M. (Elsevier Science Ltd, www.elsevier.com/locate/aca, NaN, 2012)[more][less]
Abstract: Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II)>Cu(II)>Cd(II)>Ni(II)>Mn(II) and Zn(II)>Cu(II)>Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn>Cd >Cu> Ni>Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8. URI: http://hdl.handle.net/10311/1039 Files in this item: 1
Obuseng_ACA_2012.pdf (886.0Kb) -
Mapolelo, M.; Torto, N. (Elsevier; www.elsevier.com/locate/talanta, NaN, 2004)[more][less]
Abstract: [Please note that chemical formulae do not display correctly in this abstract]. Sorption properties of baker's yeast cells, characterised as Saccharomyces cerevisiae were evaluated for trace enrichment of metal ions: Cd2+, Cr3+, Cr6+, Cu2+, Pb2+ and Zn2+ from aqueous environments. Metal concentration was determined by flame atomic absorption spectrometry (FAAS). Parameters affecting metal uptake such as solution pH, incubation time, amount of yeast biomass and effect of glucose concentration (energy source) were optimised. Further studies were carried out to evaluate the effects on metal uptake after treating yeast with glucose as well as with an organic solvent. The results showed that trace enrichment of the metals under study with yeast, depends upon the amount of yeast biomass, pH and incubation time. Treatment of yeast cells with 10-20mM glucose concentration enhanced metal uptake with exception to Cr6+, whose metal enrichment capacity decreased at glucose concentration of 60 mM. Of the investigated organic solvents THF and DMSO showed the highest and lowest capacity, respectively, to enhance metal uptake by yeast cells. Trace enrichment of metal ions from stream water, dam water, treated wastewater from a sewage plant and wastewater from an electroplating plant achieved enrichment factors (EF) varying from 1 to 98, without pre-treatment of the sample. pH adjustment further enhanced the EF for all samples. The results from these studies demonstrate that yeast is a viable trace metal enrichment media that can be used freely suspended in solution to achieve very high EF in aquatic environments. URI: http://hdl.handle.net/10311/156 Files in this item: 2
license.txt (1.998Kb)mapolelotortonew.pdf (469.7Kb) -
Ngamba, D.; Awouafack, M.; Tane, P.; Bezabih, M.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2007)[more][less]
Abstract: Gladiolus psittascinus HOOK, an herbaceous plant, is propagated by its bulb. This onion-looking plant occurs in rocky places in western province of Cameroon. The bulbs are used to treat asthma, gonorrhoea, diabetes and intestinal parasites (Adjanohoun et al., 1990). The bulbs of G. psittascinus were collected in Dschang (West Province of Cameroon) in July 2005 and identified by Mr Francois Nana, a botanist at the National Herbarium, Yaounde where a voucher specimen (55925 HCN) is deposited. We report here the isolation and structural elucidation from the chloroform extract of two new anthraquinones namely: 1,6,7-trihydroxy-3-methoxy-8-methyl-anthraquinone (1) and 1-hydroxy-3,6,7-trimethoxy-8-methyl-anthraquinone (2) along with four known compounds. The structures of the compounds were elucidated by spectroscopic analysis, mainly, 1D and 2D NMR and by comparing their physical (mp) and spectroscopic (Table 1) data with those reported in the literature. URI: http://hdl.handle.net/10311/248 Files in this item: 4
license.txt (1.998Kb)license.txt (1.998Kb)license.txt (1.998Kb) -
Mazimba, O.; Majinda, R.R.; Modibedi, C.; Masesane, I.B.; Cencicˇ, A.; Chingwaru, W. (Elsevier Science Ltd, http://www.elsevier.com/locate/bmc, NaN, 2011)[more][less]
Abstract: The investigation of Tylosema esculentum (Morama) husks, cotyledons, and tuber yielded griffonilide 2, compound 1, griffonin 3, gallic acid 4, protocatechuic acid 5, b-sitosterol 6, behenic acid 7, oleic acid 8, sucrose 9, 2-O-ethyl-a-D-glucopyranoside 10, kaempferol 11 and kaempferol-3-O-b-D-glucopyranoside 12. The structures of the isolates were determined by NMR, HR-TOF EIMS, IR and UV–vis spectroscopy, and by comparison with literature data. The husk EtOAc and n-butanol extracts demonstrated >90% DPPH radical scavenging activity at concentrations of 25, 50 and 250 lg/mL. Furthermore the husk extracts showed higher total phenolic content (233 mg GAE/g). The extractives exhibited minimum inhibitory quantities of 50–100 lg or no activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans. The tuber extracts were inactive against Caco-2 and Hela cell lines, while the husk extracts showed low activity against Caco-2 and Vero cell line with IC50 values >400 lg/mL. The GC–MS analysis showed the beans and tuber non-polar (n-hexane) extracts major constituents as fatty acids. URI: http://hdl.handle.net/10311/1029 Files in this item: 1
Mazimba_BMC_2011.pdf (698.8Kb) -
Mazimba, O.; Majinda, R.R.; Masesane, I.B. (Elsevier Science Ltd, http://www.elsevier.com/locate/tetlet, NaN, 2009)[more][less]
Abstract: A 1,2-hydride shift in the phosphoric acid-promoted cyclodimerization of styrene oxide and its chloro derivatives under solvent-free conditions leading to 2,4-disubstituted 1,3-dioxolanes is described. Methoxy substituents on the aromatic ring of the styrene oxide prevent the 1,2-hydride shift reaction leading to substituted 1,4-dioxanes. A possible mechanism for the formation of the 1,3-dioxolanes is proposed. URI: http://hdl.handle.net/10311/1026 Files in this item: 1
Masesane_TL_2009.pdf (246.5Kb) -
Goodwin, J.W.; Hughes, R.W.; Reynolds, P.A.; Kwaambwa, H.M. (Elsevier B.V. www.elsevier.com/locate/colsurfa, NaN, 2004)[more][less]
Abstract: A series of well characterised cis-poly(isoprene) (PIP) polymers (Mw = 1180, 8000, 28 300, 31 500, 86 000, 115 000 and 130 000) have been added to dispersions of poly(12-hydroxystearic acid) (PHS) coated poly(methylmethacrylate) (PMMA) particles in dodecane. The ratio of particle size to adsorbed layer was also varied. For a given added polymer molecular weight, the polymer concentration in the continuous phase covered the dilute, semi-dilute and concentrated regimes as defined by the critical concentrations c and c . The viscosity behaviour of latex dispersions with added polymer were similar for all latex/polymer combinations except when polymer Mw = 1180 was added. In the latter case, the effect of adding polymer reduced both the viscosity and shear thinning behaviour. This supports the contention that the lower molecular weight polymer acts more like a diluent than a depletent. The behaviour of the viscosity ratio (the viscosity of the dispersion relative to that of the medium) as a function of polymer concentration increased with an increase in the polymer concentration until some critical concentration (cmax) for all polymers except for a polymer molecular weight 1180 Daltons. The addition of the polymer Mw = 8000 gave the highest viscosity ratio values in the polymer concentration range studied. It was found that the viscosity of all latex/polymer combinations decreased with an increase in temperature. The results suggest that the viscosity behaviour cannot be explained on the basis of a simple steric–elastic model and require a modified theoretical treatment. URI: http://hdl.handle.net/10311/324 Files in this item: 1
Viscosity behaviiour of particles.pdf (4.522Mb) -
Kwaambwa, H.M.; Goodwin, J.W.; Hughes, R.W.; Reynolds, P.A. (Elsevier B.V. www.elsevier.com/locate/colsurfa, NaN, 2007)[more][less]
Abstract: Aseries of six well characterised homopolymers of cis-polyisoprene (PIP) ranging from 1180 to 115,000 molecular weight were utilised to explore viscosity and the scaling relationship between viscosity and concentration in dodecane (good solvent). For each polymer molecular weight, the relative viscosity of PIP in dodecane at 298K was measured at several polymer concentrations using capillary viscometry. The linear extrapolation of experimental data based on Huggins, Kramer, Martin and Schulz-Blaschke equations was used to find the intrinsic viscosity at infinite dilution for each polymer molecular weight. The single-point method of evaluation of the intrinsic viscosity was also used for comparison. The Mark-Houwink fit of the data gave power index of 0.72 indicating that dodecane is good solvent for PIP and the latter exists in solution as open flexible coil. Both the radius of gyration and critical chain overlap concentration, c*, were derived from measured intrinsic viscosities. Plot of the relative viscosities versus the scaled concentration c/c*, resulted in single curve with slope value 4.44×10−2 and correlation coefficient r2 = 0.996, indicating good linear fit. URI: http://hdl.handle.net/10311/328 Files in this item: 1
Viscosity molecular weight.pdf (3.079Mb) -
Ddamba, W.A.A.; Mokate, O. (Journal of Solution Chemistry., NaN, 2006)[more][less]
Abstract: Densities (ρ) of the binary systems of {difurylmethane+(ethanol or propan-1- ol or butan-1-ol or pentan-1-ol or hexan-1-ol)} have been measured with an Anton Paar DMA 4500 vibrating-tube densimeter over the entire composition range at 298.15K and atmospheric pressure. Excess molar volumes (V E m ) of each binary system were determined and correlated by the Redlich-Kister equation. Limiting (Vi E,∞) and excess partial molar volumes (V E i ) of components of each binary system have been calculated to provide insight into the intermolecular interactions present and the packing efficiencies. The results have been discussed in terms of specific intermolecular interactions, dispersive forces and structural effects. URI: http://hdl.handle.net/10311/318 Files in this item: 1
Volumetric prop.pdf (3.737Mb) -
Ahmad, J.; Ddamba, W.A.A. (Chemic Publishing Co., http://www.asianjournalofchemistry.com/, NaN, 2006)[more][less]
Abstract: The expression for mechanical work obtained in the expansion of a gas commonly used in physical chemistry textbooks is critically examined. The mathematical form of the first law of thermodynamics is arrived at by a procedure that is consistent with the common definition of mechanical work. The treatment is extended to explain the concept of reversible and irreversible work. URI: http://hdl.handle.net/10311/225 Files in this item: 2
license.txt (1.998Kb)Work in thermodynamics.pdf (1.197Mb)
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Now showing items 59-69 of 69