Grace Ogunlusi
Obafemi Awolowo University,Ile-Ife,Nigeria, Chemistry, Faculty Member
Viscometric study of the effect of five electrolyte additives (HCl, HClO4, HNO3, Na2SO4 and NaCl) on the critical micelle concentration of a nonionic surfactant, Triton X-100, was investigated at 30 0C using U-type Ostwald viscometer.... more
Viscometric study of the effect of five electrolyte additives (HCl, HClO4, HNO3, Na2SO4 and NaCl) on the critical micelle concentration of a nonionic surfactant, Triton X-100, was investigated at 30 0C using U-type Ostwald viscometer. Density measurements of Triton X-100 solutions in the presence of varying electrolyte concentrations were carried out using pycnometer. The electrolytes were studied in the concentration range 0 – 0.1 mol dm-3. All the electrolytes were observed to lower the critical micelle concentration (CMC) of TritonX-100 significantly in the concentration range studied with HCl having the highest CMC decreasing effect up to a factor of over 400. The results have been explained based on salting-out effect. The observed trend of the CMC lowering effect of the acids: HClO4 < HNO3 < HCl followed the Hofmeister series while greater CMC reducing effect of Na2SO4 than that of NaCl can be attributed to ionic strength effect. Key words: additives, critical micelle c...
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Chelates of β – diketones (R 1 COCH 2 COR 2 ) with transition metals have been found to possess a wide range of properties and application, some of which are dependent on the substituents (R 1 and R 2 ). Copper(II) and Nickel(II)... more
Chelates of β – diketones (R 1 COCH 2 COR 2 ) with transition metals have been found to possess a wide range of properties and application, some of which are dependent on the substituents (R 1 and R 2 ). Copper(II) and Nickel(II) complexes of β – diketones in which R 1 = C 6 H 5 and R 2 = C 6 H 5 (dbm), R 2 = CH 3 (bza) R 2 = CF 3 (tfpbd) and R 1 = C 4 H 3 S, R 2 = CF 3( tta) were synthesised and characterised using UV, IR, elemental analysis and magnetic susceptibility. The probable influence of the substituents on the kinetics and mechanisms of formation of the complexes were investigated with the aid of a Thermostated Schimadu 1800 uv-visible spectrophotometer. The reactions were studied at wavelengths characteristics of each complex. Results show the six coordinate copper(II) and nickel(II) complexes have probable distorted octahedral geometry while the four coordinate Ni(dbm) 2 is tetrahedral. The kinetics data suggests an influence of the diketonate substituents on the copper...
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The study focused on Nigeria's polyurethane (PU) production process as a test case. Though it is currently insignificant when viewed from a global perspective, PU production in Nigeria is not eco‐friendly. Traditionally, PU is... more
The study focused on Nigeria's polyurethane (PU) production process as a test case. Though it is currently insignificant when viewed from a global perspective, PU production in Nigeria is not eco‐friendly. Traditionally, PU is produced by reacting petro‐based polyol with a poly‐isocyanate, which is made from amines and phosgene and are currently imported into the country. These two materials are detrimental to the human health and environment, indicating that Nigeria's PU industries need to re‐examine their production inputs for environmental compliance. The objective of this study is to review the PU industry for nontoxic reagents that could be sourced locally vis‐à‐vis overcoming sustainable development (greening the economy) challenges in Nigeria. Non‐isocyanate polyurethane (NIPU) is preferred to petro‐polyurethane because, in comparison, NIPU has improved thermal and chemical resistance, porosity and water absorption, and is less toxic. Engaging local resources to produ...
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This study investigated the nucleophilic substitution reaction mechanisms of 5 oxatriquinane derivatives, namely: oxatriquinane (OTQ), 1,4,7-trimethyloxatriquinane (TMO), 1,4,7-triethyloxatriquinane (TEO),... more
This study investigated the nucleophilic substitution reaction mechanisms of 5 oxatriquinane derivatives, namely: oxatriquinane (OTQ), 1,4,7-trimethyloxatriquinane (TMO), 1,4,7-triethyloxatriquinane (TEO), 1,4,7-tri-iso-propyloxatriquinane (TIO) and 1,4,7-tri-tert-butyloxatriquinane (TTO). In addition to the G3 conformation (one with the substituent groups at 1,4 and 7 positions pointing into the plane of the paper) originally proposed by the previous workers, Mascal et al. in 2008 and Gunbas et al. in 2013, one more geometrical isomer was considered again for each of the derivatives, the 2G1 isomer (one in which only 2 of the 3 substituent groups at 1,4 and 7 positions are into the paper plane). Geometry optimization and determination of transition state properties of the conformers corresponding to each molecule (in the presence of azide ion, N3-) provided theoretical evidences on the possible reaction mechanisms. The 2G1 conformer for TTO was found to be unstable. The reactions o...
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ABSTRACT Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the... more
ABSTRACT Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the conductometric method. Specific conductivity was measured for SLS/NaBz/water and SLS/NaSal/water systems to determine the critical micelle concentration (cmc). Using the regular solution theory for non-ideal mixing, the pairwise interaction parameter, β12, and micellar composition, χ, were estimated in the mixed micelle. The cmc values of the surfactant–hydrotropes mixtures were generally lower than those predicted from the ideal mixing theory. The β12 values are generally negative for the two systems at all mole fractions with an average value of −2.83 for the SLS/NaBz and −3.31 for SLS/NaSal systems, respectively, indicative of a strong attractive interaction between the SLS/NaBz and SLS/NaSal mixed micelle. The calculated thermodynamic parameters of micellisation all indicated spontaneity in mixed-micelle formation for the systems studied.
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Theoretical study of the molecular geometries, electronic and thermodynamic properties of dipyrido-(3,2-a:,-c)-phenazine (dppz) was carried out in the gas phase under standard conditions using PM6 Hamiltonian in semiempirical model.... more
Theoretical study of the molecular geometries, electronic and thermodynamic properties of dipyrido-(3,2-a:,-c)-phenazine (dppz) was carried out in the gas phase under standard conditions using PM6 Hamiltonian in semiempirical model. Effects of chlorine substituents on these properties were also investigated. The results showed that all the electronic and thermodynamic properties investigated were affected by the number and relative position of chlorine substituents. Variations in some properties are not significant for some isomeric congeners, having the same number of chlorine substituents, while a number of properties showed general variation with both the number and position of chlorine substituents. Successive addition of one chlorine atom after the other at adjacent position to the last chlorine substituent increases the total energy by 241 eV and decreases the LUMO-HOMO gap by an average value of 0.124 eV. Geometry and energy optimization show that all the molecules considered...
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ABSTRACT The reactions between decakis(isopropylisocyanide)dicobalt(II), present as [Co(CNCHMe2)5]2+ in solution, and three triaryl phosphines, PPh3, P(C6H4Me-p)3, and P(C6H4OMe-p)3, have been studied in dichloromethane. The reactions... more
ABSTRACT The reactions between decakis(isopropylisocyanide)dicobalt(II), present as [Co(CNCHMe2)5]2+ in solution, and three triaryl phosphines, PPh3, P(C6H4Me-p)3, and P(C6H4OMe-p)3, have been studied in dichloromethane. The reactions were investigated under pseudo first-order conditions at different temperatures. A combination of conventional, stopped-flow, and infrared spectroscopy was employed in order to gain insight into the reaction mechanisms. Addition of each of the three phosphines to the Co(II) complex results in a shift in the λ max followed by increase and/or decrease in absorbance at the new wavelength. The triaryl phosphines react in the order P(C6H4OMe-p)3 ≫ P(C6H4Me-p)3 &gt; PPh3. This is explained in terms of the electron-donating/π-acceptor properties of the phosphines. The reactions are proposed to proceed via a number of reaction pathways including ligand substitution, ligand rearrangement, disproportionation, and reduction.
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ABSTRACT The kinetics of the oxidation of tris(2,2′-bipyridyl)iron(II) and tris(1,10-phenanthroline)iron(II) complexes ([Fe(LL)3]2+, LL = bipy, phen) by nitropentacyanocobaltate(III) complex [Co(CN)5NO2]3− was investigated in acidic... more
ABSTRACT The kinetics of the oxidation of tris(2,2′-bipyridyl)iron(II) and tris(1,10-phenanthroline)iron(II) complexes ([Fe(LL)3]2+, LL = bipy, phen) by nitropentacyanocobaltate(III) complex [Co(CN)5NO2]3− was investigated in acidic aqueous solutions at ionic strength of I = 0.1 mol dm−3 (HCl/NaCl). The reactions were carried out at fixed acid concentration ([H+] = 0.01 mol dm−3) and the temperature maintained at 35.0 ± 0.1 °C. Spectroscopic evidence is presented for the protonated oxidant. Protonation constants of 360.43 and 563.82 dm3 mol−1 were obtained for the monoprotonated and diprotonated Co(III) complexes respectively. Electron transfer rates were generally faster for [Fe(bipy)3]2+ than [Fe(phen)3]2+. The redox complexes formed ion-pairs with the oxidant with increasing concentration of the oxidant over that of the reductant. Ion-pair constants for these reaction were 160.31 and 131.9 dm3 mol−1 for [Fe(bipy)3]2+ and [Fe(phen)3]2+, respectively. The activation parameters measured for these systems have values as follows: ∆H ≠ (kJ K−1 mol−1) = +113.4 ± 0.4 and +119 ± 0.3; ∆S ≠ (J K−1) = +107.6 ± 1.3 and 125.0 ± 1.6; ∆G ≠ (kJ K−1) = +81 ± 0.4 and +82.4 ± 0.4; and E a (kJ mol−1) = 115.9 ± 0.5 and 122.3 ± 0.6 for LL = bipy and phen, respectively. Effect of added anions (Cl−, $ {\text{SO}}_{4}^{2 - } $ and $ {\text{ClO}}_{4}^{ - } $ ) on the systems showed decrease in the electron transfer rate constant. An outer-sphere mechanism is proposed for the reaction.
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Abstract The kinetics of the reactions between azido-pentacyanocobaltate(III), Co(CN)5N3 3-, and iron(II) poly-pyridyl complexes, Fe(LL)3 2? (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol... more
Abstract The kinetics of the reactions between azido-pentacyanocobaltate(III), Co(CN)5N3 3-, and iron(II) poly-pyridyl complexes, Fe(LL)3 2? (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol dm-3 NaCl. The reactions were carried ...
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Micellisation of sodium dodecyl sulphate (SDS) was studied in the presence of hydrochloric acid (HCl) and perchloric acid (HClO4) using conductometry method. The conductivity-[SDS] plots showed abnormal profile pattern at [HCl] > 0.002... more
Micellisation of sodium dodecyl sulphate (SDS) was studied in the presence of hydrochloric acid (HCl) and perchloric acid (HClO4) using conductometry method. The conductivity-[SDS] plots showed abnormal profile pattern at [HCl] > 0.002 mol dm−3 and [HClO4] > 0.001 mol dm−3. Below these acid concentrations, conductivity pattern was normal, and the critical micelle concentration (CMC) values of SDS were lower in both acids than in water. At high acid concentrations, post-micellar slopes were negative. Fourier transform infrared (FTIR) analysis showed significant shifts in the bands suggesting the formation of dodecyl hydrogen sulphate by SDS at high acid concentrations. Thermodynamic parameters for SDS micellisation at low acid concentrations ([HCl] = 0.002 mol dm−3 and [HClO4] = 0.001 mol dm−3) were determined in the temperature range 15–40°C. As temperature increases, the change in enthalpy and entropy of micellisation becomes less positive, and the change in free energy of micellisation becomes increasingly negative.
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ABSTRACT The critical micelle concentrations of binary mixtures of sodium dodecylsulphate (SDS) and sodium lauroylsarcosinate (SLAS) have been determined in water by conductivity measurements at different mole fractions for each of the... more
ABSTRACT The critical micelle concentrations of binary mixtures of sodium dodecylsulphate (SDS) and sodium lauroylsarcosinate (SLAS) have been determined in water by conductivity measurements at different mole fractions for each of the components. The critical micelle concentrations were slightly lower than that predicted from ideal mixing theory indicating positive synergistic interactions in mixed micelle formation. The results of the mixed systems were analysed using the Regular Solution Theory and the approach based on the Gibbs–Duhem equation which allowed for the determination of the composition of the mixed micelle, the activity coefficients and the pair-wise molecular interaction parameter β. The β values were all negative at all mole fractions investigated, showing a slight deviation from ideality, with an average value of –0.27. The excess free energy of the mixed systems was also calculated and the values were all negative for the mixed systems studied, an indication that the mixed micelles are thermodynamically stable relative to the individual component. This thermodynamic parameter also exhibits symmetrical behaviour with respect to micellar composition suggestive of a regular solution behaviour of the mixed surfactant system
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ABSTRACT Electron transfer reaction between [Fe(bipy)3]2+ and [Co(CN)5N3]3− has been studied in aqueous solutions of SDS, Triton X-100 and SDS/Triton X-100 mixtures. SDS inhibited the electron transfer reaction with inhibition factor... more
ABSTRACT Electron transfer reaction between [Fe(bipy)3]2+ and [Co(CN)5N3]3− has been studied in aqueous solutions of SDS, Triton X-100 and SDS/Triton X-100 mixtures. SDS inhibited the electron transfer reaction with inhibition factor kψ/kw, in the range 1.00 ≤ kψ/kw ≤ 2.53 while Triton X-100 showed no significant effect on the reaction. Binding parameters were obtained using Piszkiewicz model with cooperativity index n = 2.184 in the presence of SDS. Binary mixture of surfactants Triton X-100/SDS exhibit inhibition of the reaction at low concentrations of Triton X-100 with relative rate enhancement as the mixture becomes richer in Triton X-100. The results were explained in terms of strong electrostatic and/or hydrophobic interactions between the surfactants and the substrates.
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The rates of chemical reactions are known to be al-tered or modified by self-organized assemblies such as micelles. This phenomenon has received considerable at-tention from many workers in recent past.116 Results from such... more
The rates of chemical reactions are known to be al-tered or modified by self-organized assemblies such as micelles. This phenomenon has received considerable at-tention from many workers in recent past.116 Results from such investigations provided evidence that surfactant ...
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The kinetics of the reactions between Fe(phen)3 ... 2+ [phen = tris(1,10) phenanthroline] and Co(CN)5X3Ā (X = Cl, ... Br or I) have been investigated in aqueous acidic solutions at I=0.1 mol dm ... )3 ) and the second-order rate... more
The kinetics of the reactions between Fe(phen)3 ... 2+ [phen = tris(1,10) phenanthroline] and Co(CN)5X3Ā (X = Cl, ... Br or I) have been investigated in aqueous acidic solutions at I=0.1 mol dm ... )3 ) and the second-order rate constants for the ... )1 s )1 . Ion-pair constants Kip for ...