Isolation of and interaction of nutrients with the linoleoyl-coa desaturase complex
- Authors: Perkins, Denise Mary
- Date: 1990
- Subjects: Cell proliferation , Cancer cells -- Growth -- Regulation , Enzymes -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4558 , http://hdl.handle.net/10962/d1018264
- Description: The termina1 enzyme in the linoleoyl-CoA desaturase enzyme complex, delta-6-desaturase was implied in the control of cell proliferation in cancer cells. One of the aims of this study was to isolate the terminal enzyme. It was decided that in order to isolate this enzyme it was first necessary to isolate the entire complex and then to enzymatically solubilise the first two components of the complex i e cytochrome b5 reductase and cytochrome b5 from the complex resulting in a pure delta-6-desaturase . The first two components were isolated and purified using simplified and easily reproducible methodologies which could be utilised in the final purification of delta-6- desaturase. The entire enzyme complex, linoleoyl-CoA desaturase was also isolated in a pure form and this pure complex was used to attempt to isolate delta-6-desaturase. The terminal enzyme was isolated with some cytochrome b5 still bound to it. The methods used had proven to be successful and with some modifications should yield a pure enzyme. Zinc and GLA were known to play a role in the inhibition of cancer cell proliferation and zinc was hypothesised to inhibit cell growth by stimulating the activity of the linoleoyl-CoA desaturase enzyme complex which is involved in the regulation of cell proliferation. GLA is the product of the reaction that this enzyme complex catalyses and GLA has been shown to inhibit cancer ce ll growth. The effect of GLA on cell growth and linoleoyl-CoA desaturase activity was thus investigated. Results showed that both zinc and GLA inhibited cell growth and that the combined addition of zinc and GLA generally resulted in the inhibition of cell growth and the activation of linoleoyl-CoA desaturase activity in the BL-6 cells while having a less pronounced effect on the LLCMK cells. The results of this study support the hypothesis that zinc may be a cofactor of linoleoyl-CoA desaturase.
- Full Text:
- Date Issued: 1990
- Authors: Perkins, Denise Mary
- Date: 1990
- Subjects: Cell proliferation , Cancer cells -- Growth -- Regulation , Enzymes -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4558 , http://hdl.handle.net/10962/d1018264
- Description: The termina1 enzyme in the linoleoyl-CoA desaturase enzyme complex, delta-6-desaturase was implied in the control of cell proliferation in cancer cells. One of the aims of this study was to isolate the terminal enzyme. It was decided that in order to isolate this enzyme it was first necessary to isolate the entire complex and then to enzymatically solubilise the first two components of the complex i e cytochrome b5 reductase and cytochrome b5 from the complex resulting in a pure delta-6-desaturase . The first two components were isolated and purified using simplified and easily reproducible methodologies which could be utilised in the final purification of delta-6- desaturase. The entire enzyme complex, linoleoyl-CoA desaturase was also isolated in a pure form and this pure complex was used to attempt to isolate delta-6-desaturase. The terminal enzyme was isolated with some cytochrome b5 still bound to it. The methods used had proven to be successful and with some modifications should yield a pure enzyme. Zinc and GLA were known to play a role in the inhibition of cancer cell proliferation and zinc was hypothesised to inhibit cell growth by stimulating the activity of the linoleoyl-CoA desaturase enzyme complex which is involved in the regulation of cell proliferation. GLA is the product of the reaction that this enzyme complex catalyses and GLA has been shown to inhibit cancer ce ll growth. The effect of GLA on cell growth and linoleoyl-CoA desaturase activity was thus investigated. Results showed that both zinc and GLA inhibited cell growth and that the combined addition of zinc and GLA generally resulted in the inhibition of cell growth and the activation of linoleoyl-CoA desaturase activity in the BL-6 cells while having a less pronounced effect on the LLCMK cells. The results of this study support the hypothesis that zinc may be a cofactor of linoleoyl-CoA desaturase.
- Full Text:
- Date Issued: 1990
Synthetic and spectrometric investigation of 1,4-benzoxazepines
- Authors: Whittal, R D
- Date: 1990
- Subjects: Spectrum analysis , Benzodiazepines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4381 , http://hdl.handle.net/10962/d1005046
- Description: Flavanone (2,3-dihydro-2-phenyl-4H-benzopyran-4-one) and a series of 4'- and 7-halogeno derivatives were prepared from the corresponding 2'-hydroxychalcones [1-(2-hydroxyphenyl)-3-phenyl-2-propen-l-ones], which, in turn, were synthesized by aldol condensation of substituted 2'-hydroxacetophenones with various benzaldehydes. A series of 2,3-dihydro-2-phenyl-l,4-benzoxazepin-5(4H)-ones were prepared by ring expansion of the corresponding flavanones, via the Schmidt reaction, using trimethylsilylazide and trifluoroacetic acid. A series of tetrazoles {2,3-dihydro-2-phenyl-tetrazolo[1,5-d]-1,4-benzoxazepines} were also isolated as by-products of the Schmidt reaction. Flavanone oxime was synthesized for use in Beckmann reactions, and its molecular structure was determined by x-ray crystallography. Attempts to prepare 1,4-benzoxazepinone or its 1,5-analogue via Beckmann rearrangement of flavanone oxime, with polyphosphoric acid or phosphorus pentachloride catalysts, however, were unsuccessful. Several methods for introducing Δ²-unsaturation into the benzoxazepinone system were also examined. High resolution ¹H n.m.r., computer modelling, and molecular mechanics techniques were used to determine the conformations of the heterocycles of the benzoxazepinones and tetrazoles and results are compared with earlier studies in this field. Certain trends in the fragmentation patterns were observed in the low resolution mass spectra of the benzoxazepinones and tetrazoles, and high resolution mass spectrometric data were used to explore the major fragmentation patterns of these compounds.
- Full Text:
- Date Issued: 1990
- Authors: Whittal, R D
- Date: 1990
- Subjects: Spectrum analysis , Benzodiazepines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4381 , http://hdl.handle.net/10962/d1005046
- Description: Flavanone (2,3-dihydro-2-phenyl-4H-benzopyran-4-one) and a series of 4'- and 7-halogeno derivatives were prepared from the corresponding 2'-hydroxychalcones [1-(2-hydroxyphenyl)-3-phenyl-2-propen-l-ones], which, in turn, were synthesized by aldol condensation of substituted 2'-hydroxacetophenones with various benzaldehydes. A series of 2,3-dihydro-2-phenyl-l,4-benzoxazepin-5(4H)-ones were prepared by ring expansion of the corresponding flavanones, via the Schmidt reaction, using trimethylsilylazide and trifluoroacetic acid. A series of tetrazoles {2,3-dihydro-2-phenyl-tetrazolo[1,5-d]-1,4-benzoxazepines} were also isolated as by-products of the Schmidt reaction. Flavanone oxime was synthesized for use in Beckmann reactions, and its molecular structure was determined by x-ray crystallography. Attempts to prepare 1,4-benzoxazepinone or its 1,5-analogue via Beckmann rearrangement of flavanone oxime, with polyphosphoric acid or phosphorus pentachloride catalysts, however, were unsuccessful. Several methods for introducing Δ²-unsaturation into the benzoxazepinone system were also examined. High resolution ¹H n.m.r., computer modelling, and molecular mechanics techniques were used to determine the conformations of the heterocycles of the benzoxazepinones and tetrazoles and results are compared with earlier studies in this field. Certain trends in the fragmentation patterns were observed in the low resolution mass spectra of the benzoxazepinones and tetrazoles, and high resolution mass spectrometric data were used to explore the major fragmentation patterns of these compounds.
- Full Text:
- Date Issued: 1990
An investigation into the properties of cotton fibres as used in nonwoven fabrics
- Authors: Lutseke, Nothando Sazikazi
- Date: 1989
- Subjects: Cotton -- Analysis , Fibers -- Analysis , Nonwoven fabrics -- Analysis , Textile chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4552 , http://hdl.handle.net/10962/d1018241
- Description: The purpose of this investigation was to determine the properties that characterise cotton fibres in the various stages in the CPNF process as well as to determine which fibre characteristics a r e required to entangle the fibres to produce a successful CPNF . The criteria adopted in this work for a successful CPNF include: 1. the tensile strength of the fabrics 2. a well-defined pattern 3. absorbency and wicking The properties selected for investigation were 1. the cotton fibre surface (using SEM and DSC analyses) 2. the degree of degradation of the cotton fibre as a result of the CPNF process (using cellulose fluidity measurements) 3. the non-cellulosic content of the fibre (using IR, DSC, and Chemical analyses) 4. fibre friction 5. absorbency and wicking 6. tensile properties Analysis of the results indicates clearly what the fundamental properties of the cotton fibre must be for a successful cotton CPNF to be manufactured. The conclusions also indicate the necessary properties a man-made fibre must have to produce a successful CPNF.
- Full Text:
- Date Issued: 1989
- Authors: Lutseke, Nothando Sazikazi
- Date: 1989
- Subjects: Cotton -- Analysis , Fibers -- Analysis , Nonwoven fabrics -- Analysis , Textile chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4552 , http://hdl.handle.net/10962/d1018241
- Description: The purpose of this investigation was to determine the properties that characterise cotton fibres in the various stages in the CPNF process as well as to determine which fibre characteristics a r e required to entangle the fibres to produce a successful CPNF . The criteria adopted in this work for a successful CPNF include: 1. the tensile strength of the fabrics 2. a well-defined pattern 3. absorbency and wicking The properties selected for investigation were 1. the cotton fibre surface (using SEM and DSC analyses) 2. the degree of degradation of the cotton fibre as a result of the CPNF process (using cellulose fluidity measurements) 3. the non-cellulosic content of the fibre (using IR, DSC, and Chemical analyses) 4. fibre friction 5. absorbency and wicking 6. tensile properties Analysis of the results indicates clearly what the fundamental properties of the cotton fibre must be for a successful cotton CPNF to be manufactured. The conclusions also indicate the necessary properties a man-made fibre must have to produce a successful CPNF.
- Full Text:
- Date Issued: 1989
Synthetic studies of swazinecic acid dilactone
- Authors: Liddell, James Richard
- Date: 1989
- Subjects: Phrrolizidines Alkaloids -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4298 , http://hdl.handle.net/10962/d1004668
- Description: The occurrence and syntheses of the pyrrolizidine alkaloids from 1976 to March 1988 is reviewed, and a stereoselective total synthesis of swazinecic acid dilactone was attempted. One approach involved an asymmetric synthesis of the allylic α-hydroxy acid 2-hydroxy-2,3-dimethyl-3-butenoic acid employing oxazolines as chiral auxilaries. The oxazoline, (4S,5S)-2-(1-bromoethyl)-4-methoxymethyl-5-phenyl-2-oxazoline, was obtained by direct halogenation of the 2-ethyl oxazoline analogue. This was condensed with acetone in a Darzens type reaction and the resultant epoxy oxazoline rearranged to an allylic α-hydroxy oxazoline which was then hydrolysed to the chiral hydroxy acid in low enantiomeric excess. The hydroxy acid, as the O-silylated ethyl ester, was elaborated by allylic diethyl malonate to bromination and condensation with diethyl 5-carboethoxy-2-methyl-3- methylene-2-0-tert-butyldimethylsilylhexanedioate. Removal of the silyl protecting group and epoxidation provided an epoxy triester, which on hydrolysis provided a mixture of acids of uncertain structures.
- Full Text:
- Date Issued: 1989
- Authors: Liddell, James Richard
- Date: 1989
- Subjects: Phrrolizidines Alkaloids -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4298 , http://hdl.handle.net/10962/d1004668
- Description: The occurrence and syntheses of the pyrrolizidine alkaloids from 1976 to March 1988 is reviewed, and a stereoselective total synthesis of swazinecic acid dilactone was attempted. One approach involved an asymmetric synthesis of the allylic α-hydroxy acid 2-hydroxy-2,3-dimethyl-3-butenoic acid employing oxazolines as chiral auxilaries. The oxazoline, (4S,5S)-2-(1-bromoethyl)-4-methoxymethyl-5-phenyl-2-oxazoline, was obtained by direct halogenation of the 2-ethyl oxazoline analogue. This was condensed with acetone in a Darzens type reaction and the resultant epoxy oxazoline rearranged to an allylic α-hydroxy oxazoline which was then hydrolysed to the chiral hydroxy acid in low enantiomeric excess. The hydroxy acid, as the O-silylated ethyl ester, was elaborated by allylic diethyl malonate to bromination and condensation with diethyl 5-carboethoxy-2-methyl-3- methylene-2-0-tert-butyldimethylsilylhexanedioate. Removal of the silyl protecting group and epoxidation provided an epoxy triester, which on hydrolysis provided a mixture of acids of uncertain structures.
- Full Text:
- Date Issued: 1989
The kinetics and mechanism of the oxidation of chromium (III) chloride
- Authors: Sole, Kathryn Clare
- Date: 1989 , 2013-08-28
- Subjects: Chromium chloride--Oxidation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4301 , http://hdl.handle.net/10962/d1004921 , Chromium chloride--Oxidation
- Description: The kinetic behaviour of anhydrous CrCl₃ in gaseous oxidising atmospheres has been examined in the temperature range 350 to 630°C in order to identify optimum reaction conditions and to establish the mechanism by which the reaction is controlled. The reaction under consideration is CrCl₃ (s) + ¾ O₂ (g) → ½ Cr₂O₃ (s) + ³/₂ Cl₂ (g). The main experimental techniques used were isothermal and programmed-temperature thermogravimetry, supplemented by scanning electron-microscopy, surface-area determinations and porosity measurements. The effects of sample pelletisation, gas flowrate, temperature, oxygen partial pressure, pellet porosity and the addition of other oxide species on the rate and extent of reaction have been studied. The reaction is shown to occur in a single step, starting at -350°C under non-isothermal conditions, and exhibiting a deceleratory rate over most of the reaction. Isothermal thermogravimetric curves were fitted to a number of kinetic rate expressions, and a series of statistical analyses used to identify the rate equation which best describes the experimental data. Supporting evidence was provided by scanning electron-microscopic examination of partially-reacted samples. It is concluded that the reaction is under chemical control, and that reaction occurs by means of a linearly-advancing reactant-product interface. The reaction kinetics can be described by a contracting-geometry rate expression. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1989
- Authors: Sole, Kathryn Clare
- Date: 1989 , 2013-08-28
- Subjects: Chromium chloride--Oxidation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4301 , http://hdl.handle.net/10962/d1004921 , Chromium chloride--Oxidation
- Description: The kinetic behaviour of anhydrous CrCl₃ in gaseous oxidising atmospheres has been examined in the temperature range 350 to 630°C in order to identify optimum reaction conditions and to establish the mechanism by which the reaction is controlled. The reaction under consideration is CrCl₃ (s) + ¾ O₂ (g) → ½ Cr₂O₃ (s) + ³/₂ Cl₂ (g). The main experimental techniques used were isothermal and programmed-temperature thermogravimetry, supplemented by scanning electron-microscopy, surface-area determinations and porosity measurements. The effects of sample pelletisation, gas flowrate, temperature, oxygen partial pressure, pellet porosity and the addition of other oxide species on the rate and extent of reaction have been studied. The reaction is shown to occur in a single step, starting at -350°C under non-isothermal conditions, and exhibiting a deceleratory rate over most of the reaction. Isothermal thermogravimetric curves were fitted to a number of kinetic rate expressions, and a series of statistical analyses used to identify the rate equation which best describes the experimental data. Supporting evidence was provided by scanning electron-microscopic examination of partially-reacted samples. It is concluded that the reaction is under chemical control, and that reaction occurs by means of a linearly-advancing reactant-product interface. The reaction kinetics can be described by a contracting-geometry rate expression. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1989
The thermodynamics of binary liquid mixtures of compounds containing multiple bonds.
- Authors: Baxter, Rodney Charles
- Date: 1989
- Subjects: Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4531 , http://hdl.handle.net/10962/d1016079
- Description: Excess thermodynamic properties have been determined for several binary liquid mixtures with the aim of testing various thermodynamic theories and postulates. Excess molar enthalpies, HEm, have been determined using an LKB flow microcalorimeter and excess molar volumes, VEm, have been determined using an Anton Paar vibrating tube densitometer. The activity coefficients at infinite dilution ƴ∞₁₃, have been determined using an atmospheric pressure gas-liquid chromatograph. The excess molar enthalpies and the excess molar volumes have been measured at 298.15 K for systems involving the bicyclic compounds decahydronaphthalene (decalin), 1,2,3,4-tetrahydronaphthalene (tetralin), bicyclohexyl, or cyclohexylbenzene mixed with 1- hexene, 1-hexyne, 1-heptene, 1-heptyne, cyclohexene, 1,3-cyclohexadiene, 1,4- cyclohexadiene, or benzene. These excess properties have also been measured for systems where the bicyclic compound has been replaced with benzene, cyclohexane or n-hexane. The results show defmite trends related to the size, shape, and the degree of unsaturation of the component molecules. The Flory theory has been used to predict excess molar enthalpies and excess molar volumes for {(a bicyclic compound or benzene or cyclohexane or n-hexane) +(an n-alkane or a 1-alkene or a 1-alkyne or a cycloalkane or cyclohexene or a cycloalkadiene or benzene)}. The one parameter equations offer reasonably good correlations between the predicted and the experimental results. More insight into the origins of the contnbutions to the excess thermodynamic properties for these systems has been gained by considering the approximate equations of Patterson and co-workers, which separate the interactional and the free volume contributions to the excess molar enthalpy and the excess molar volume. The one parameter equations have adequately rationalized a good deal of the observed behaviour for HEm and VEm. The theory of Liebermann and co-workers, which does not employ any adjustable parameters, has not been as successful at predicting the excess thermodynamic properties for the above systems. The activity coefficients at infinite dilution have been measured at 278.15 K, 288.15 K and 298.15 K for n-bexane, 1-bexene, 1-hexyne, n-heptane, 1-heptene, 1-heptyne, cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene, in decalin, tetralin, bicyclohexyl, and cyclohexylbenzene. Solvent losses from the column have been accounted for by an extrapolation procedure. The activity coefficient results together with the HEm and VEm values have been used to calculate the partial molar excess thermodynamic properties of mixing at infinite dilution. The partial molar excess properties at infinite dilution for decalin mixtures are similar to those for bicyclohexyl mixtures. There is also a similarity between the properties of the tetralin mixtures and the cyclohexylbenzene mixtures. The cycloalkadienes, benzene and the 1-alkynes exhibit a strong dissociation effect on being mixed with the saturated solvents, decalin and bicyclohexyl, but associate strongly with tetralin and with cyclohexylbenzene. The Flory theory bas been used to predict activity coefficients at infinite dilution from the experimentally determined HEm results for { (n-bexane or 1-hexene or 1-hexyne or naheptane or 1-heptene or 1-beptyne) + (a bicyclic compound)}. The theory is much better at predicting values for mixtures where both components are either saturated molecules or are unsaturated molecules than for {saturated + unsaturated} mixtures.
- Full Text:
- Date Issued: 1989
- Authors: Baxter, Rodney Charles
- Date: 1989
- Subjects: Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4531 , http://hdl.handle.net/10962/d1016079
- Description: Excess thermodynamic properties have been determined for several binary liquid mixtures with the aim of testing various thermodynamic theories and postulates. Excess molar enthalpies, HEm, have been determined using an LKB flow microcalorimeter and excess molar volumes, VEm, have been determined using an Anton Paar vibrating tube densitometer. The activity coefficients at infinite dilution ƴ∞₁₃, have been determined using an atmospheric pressure gas-liquid chromatograph. The excess molar enthalpies and the excess molar volumes have been measured at 298.15 K for systems involving the bicyclic compounds decahydronaphthalene (decalin), 1,2,3,4-tetrahydronaphthalene (tetralin), bicyclohexyl, or cyclohexylbenzene mixed with 1- hexene, 1-hexyne, 1-heptene, 1-heptyne, cyclohexene, 1,3-cyclohexadiene, 1,4- cyclohexadiene, or benzene. These excess properties have also been measured for systems where the bicyclic compound has been replaced with benzene, cyclohexane or n-hexane. The results show defmite trends related to the size, shape, and the degree of unsaturation of the component molecules. The Flory theory has been used to predict excess molar enthalpies and excess molar volumes for {(a bicyclic compound or benzene or cyclohexane or n-hexane) +(an n-alkane or a 1-alkene or a 1-alkyne or a cycloalkane or cyclohexene or a cycloalkadiene or benzene)}. The one parameter equations offer reasonably good correlations between the predicted and the experimental results. More insight into the origins of the contnbutions to the excess thermodynamic properties for these systems has been gained by considering the approximate equations of Patterson and co-workers, which separate the interactional and the free volume contributions to the excess molar enthalpy and the excess molar volume. The one parameter equations have adequately rationalized a good deal of the observed behaviour for HEm and VEm. The theory of Liebermann and co-workers, which does not employ any adjustable parameters, has not been as successful at predicting the excess thermodynamic properties for the above systems. The activity coefficients at infinite dilution have been measured at 278.15 K, 288.15 K and 298.15 K for n-bexane, 1-bexene, 1-hexyne, n-heptane, 1-heptene, 1-heptyne, cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene, in decalin, tetralin, bicyclohexyl, and cyclohexylbenzene. Solvent losses from the column have been accounted for by an extrapolation procedure. The activity coefficient results together with the HEm and VEm values have been used to calculate the partial molar excess thermodynamic properties of mixing at infinite dilution. The partial molar excess properties at infinite dilution for decalin mixtures are similar to those for bicyclohexyl mixtures. There is also a similarity between the properties of the tetralin mixtures and the cyclohexylbenzene mixtures. The cycloalkadienes, benzene and the 1-alkynes exhibit a strong dissociation effect on being mixed with the saturated solvents, decalin and bicyclohexyl, but associate strongly with tetralin and with cyclohexylbenzene. The Flory theory bas been used to predict activity coefficients at infinite dilution from the experimentally determined HEm results for { (n-bexane or 1-hexene or 1-hexyne or naheptane or 1-heptene or 1-beptyne) + (a bicyclic compound)}. The theory is much better at predicting values for mixtures where both components are either saturated molecules or are unsaturated molecules than for {saturated + unsaturated} mixtures.
- Full Text:
- Date Issued: 1989
Extractives from six species of Lamiaceae
- Davies-Coleman, Michael Trevor
- Authors: Davies-Coleman, Michael Trevor
- Date: 1988
- Subjects: Lamiaceae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4532 , http://hdl.handle.net/10962/d1016235
- Description: In continuation of the phytochemical studies of plants belonging to the Lamiaceae (formerly Labiatae) the acetone extractives of six Southern African species from this family have been examined. The genus Syncolostemon has not been investigated before and a new 6- substituted-5 ,6-dihydro-a-pyrone , synrotolide was isolated from S. rotundifolius. The structure of synrotolide was fully elucidated as 6fixii [3'R, 61S-(diacetyloxy)-4 1R, 5 1 8-(dihydroxy)-1~-hepteny~ -5,6-dihydro-2H-pyran- 2-one. Oleanolic acid is the major component of both~ rotundifolius and S. densifloris. The flavonol quercetin was isolated from S. densifloris as its 3, 3', 4' , 7 tetramethyl ether. A further 6-substituted-5,6-dihydro-a-pyrone, boronolide, was obtained from Tetradenia barberae. The structure of boronolide was known but the absolute stereochemistry was unassigned. Chemical degradation established the total structure of this compound as 6R- [1 'R, 2'R, 3's -(trisacetyloxy)heptyl] -5,6-dihydro-2H-pyran-2-one. The chemistry of naturally occuring 6-substituted-5,6-dihydro-apyrones has not as such been previously reviewed and a comprehensive review covering the literature up to June 1987 is presented here. Three known labdane diterpenoids nepetaefuran, hispanalone and dubiin were iso lated from Leonotis nepetaefolia, Ballota africana and L. ocymifolia var. ocymifolia (formerly~ dubia). Both~ nepetaefolia and L. dubia have been examined before. An X-ray analysis of saponified dubiin and a circular dichroism study of 6-deacetyldehydrodubiin and related compounds corroborated the structure of dubiin as 48, 5R, 6R, 8R, 9R, 10R-[6-acetoxy-15,16-epoxy-9-hydroxylabda-13 (16), 14-dien-19, 20- olactoneJ. The chemotaxonomic relationships of the genera Ballota and Leonotis are discussed.
- Full Text:
- Date Issued: 1988
- Authors: Davies-Coleman, Michael Trevor
- Date: 1988
- Subjects: Lamiaceae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4532 , http://hdl.handle.net/10962/d1016235
- Description: In continuation of the phytochemical studies of plants belonging to the Lamiaceae (formerly Labiatae) the acetone extractives of six Southern African species from this family have been examined. The genus Syncolostemon has not been investigated before and a new 6- substituted-5 ,6-dihydro-a-pyrone , synrotolide was isolated from S. rotundifolius. The structure of synrotolide was fully elucidated as 6fixii [3'R, 61S-(diacetyloxy)-4 1R, 5 1 8-(dihydroxy)-1~-hepteny~ -5,6-dihydro-2H-pyran- 2-one. Oleanolic acid is the major component of both~ rotundifolius and S. densifloris. The flavonol quercetin was isolated from S. densifloris as its 3, 3', 4' , 7 tetramethyl ether. A further 6-substituted-5,6-dihydro-a-pyrone, boronolide, was obtained from Tetradenia barberae. The structure of boronolide was known but the absolute stereochemistry was unassigned. Chemical degradation established the total structure of this compound as 6R- [1 'R, 2'R, 3's -(trisacetyloxy)heptyl] -5,6-dihydro-2H-pyran-2-one. The chemistry of naturally occuring 6-substituted-5,6-dihydro-apyrones has not as such been previously reviewed and a comprehensive review covering the literature up to June 1987 is presented here. Three known labdane diterpenoids nepetaefuran, hispanalone and dubiin were iso lated from Leonotis nepetaefolia, Ballota africana and L. ocymifolia var. ocymifolia (formerly~ dubia). Both~ nepetaefolia and L. dubia have been examined before. An X-ray analysis of saponified dubiin and a circular dichroism study of 6-deacetyldehydrodubiin and related compounds corroborated the structure of dubiin as 48, 5R, 6R, 8R, 9R, 10R-[6-acetoxy-15,16-epoxy-9-hydroxylabda-13 (16), 14-dien-19, 20- olactoneJ. The chemotaxonomic relationships of the genera Ballota and Leonotis are discussed.
- Full Text:
- Date Issued: 1988
The sulphidization of mineral surfaces as applied to the froth flotation process
- Authors: Ramagwede, Mudzimba Hubert
- Date: 1988 , 2013-02-28
- Subjects: Sulfide minerals , Flotation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4296 , http://hdl.handle.net/10962/d1004590
- Description: This work constitutes a fundamental study of the interaction between soluble sulphide,copper (II) oxide and cerussite particles in the presence of Ca²⁺ ,Mg²⁺ starch , gum arabic and Triton X- IOO . A detailed investigation of the effect of pH of the system on the rate of sulphide uptake was made . In addition , the structural form of the surface precipitat.es were determined with the aid of scanning electron microscopy . On the basis of these results , it was concluded that adsorption of sulphide on cerussite in the presence or absence of Ca²⁺ starch, gum arabic and Triton X-IOO could either lead to the formation of a non-uniform or a uniform sulphide layer depending on the experimental conditions . However , the interaction of copper (II) · oxide wi th soluble sulphide in the presence or absence of the above mentioned species always led to the formation or a non-uniform sulphide layer . Preliminary experiments of the interaction between xanthate and sulphidized surface showed that oxide surface covered with metal sulphide layer reacts with less xanthate than the free oxide surface.
- Full Text:
- Date Issued: 1988
- Authors: Ramagwede, Mudzimba Hubert
- Date: 1988 , 2013-02-28
- Subjects: Sulfide minerals , Flotation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4296 , http://hdl.handle.net/10962/d1004590
- Description: This work constitutes a fundamental study of the interaction between soluble sulphide,copper (II) oxide and cerussite particles in the presence of Ca²⁺ ,Mg²⁺ starch , gum arabic and Triton X- IOO . A detailed investigation of the effect of pH of the system on the rate of sulphide uptake was made . In addition , the structural form of the surface precipitat.es were determined with the aid of scanning electron microscopy . On the basis of these results , it was concluded that adsorption of sulphide on cerussite in the presence or absence of Ca²⁺ starch, gum arabic and Triton X-IOO could either lead to the formation of a non-uniform or a uniform sulphide layer depending on the experimental conditions . However , the interaction of copper (II) · oxide wi th soluble sulphide in the presence or absence of the above mentioned species always led to the formation or a non-uniform sulphide layer . Preliminary experiments of the interaction between xanthate and sulphidized surface showed that oxide surface covered with metal sulphide layer reacts with less xanthate than the free oxide surface.
- Full Text:
- Date Issued: 1988
Aspects of the anaerobic digestion of wattle tannins
- Authors: Hurlow, Elton Lloyd
- Date: 1987
- Subjects: Tanneries -- Waste disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4300 , http://hdl.handle.net/10962/d1004909
- Description: The aqueous extract from the bark of the black wattle tree, (Acacia mearnsii De Wild)(1), is used extensively in the tanning industry for the production of sole and other heavy leathers as well as in lighter leathers and skins. The commercial extract is available in an easily dissolvable spray dried form and in deference to its genus name Mimosaceae is referred to in the trade as Mimosa(3). Mimosa extract consists primarily of high molecular weight polymeric flavonoid units which also constitutes the active tanning ingredient. Lower phenolics, gums and sugars or the so called "non-tannins" are present as impurities and contribute up to 40% to (3 ) the total mass of the extract.
- Full Text:
- Date Issued: 1987
- Authors: Hurlow, Elton Lloyd
- Date: 1987
- Subjects: Tanneries -- Waste disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4300 , http://hdl.handle.net/10962/d1004909
- Description: The aqueous extract from the bark of the black wattle tree, (Acacia mearnsii De Wild)(1), is used extensively in the tanning industry for the production of sole and other heavy leathers as well as in lighter leathers and skins. The commercial extract is available in an easily dissolvable spray dried form and in deference to its genus name Mimosaceae is referred to in the trade as Mimosa(3). Mimosa extract consists primarily of high molecular weight polymeric flavonoid units which also constitutes the active tanning ingredient. Lower phenolics, gums and sugars or the so called "non-tannins" are present as impurities and contribute up to 40% to (3 ) the total mass of the extract.
- Full Text:
- Date Issued: 1987
A study of petrol and diesel fuel blends with special reference to their thermodynamic properties and phase equilibria
- Authors: Heyward, Caroline
- Date: 1986
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21167 , http://hdl.handle.net/10962/6695
- Description: The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols. Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application.
- Full Text:
- Date Issued: 1986
- Authors: Heyward, Caroline
- Date: 1986
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21167 , http://hdl.handle.net/10962/6695
- Description: The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols. Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application.
- Full Text:
- Date Issued: 1986
The adsorption of chelating reagents on oxide minerals
- Bryson, Michael Andrew Walker
- Authors: Bryson, Michael Andrew Walker
- Date: 1986
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:20969 , http://hdl.handle.net/10962/5729
- Description: This work constitutes a fundamental study of the interaction between chelating reagents and oxide minerals . The adsorption mechanisms have been elucidated for most of the systems generated by the oxides of copper(II) or iron(III) and chelating reagents octyl hydroxamate, N-phenylbenzohydroxamate, salicylaldoxime, 5-nitrosalicylaldoxime or 8-hydroxyquinoline. The results of the preliminary work on one of the systems, viz. the oxide-hydroxamate system, indicated that the classical type adsorption process, in which the reagent forms a uniform layer of chelate over the oxide surface was not applicable. Rather, the adsorption occurred via the formation of a discrete metal-chelate precipitate at the oxide surface. In order to better understand the associated with copper (II) oxide, adsorption process the oxide was recrystallized to produce a coarser material with a more uniform surface. This allowed the oxide surface to be viewed under the scanning electron microscope and also enabled the relative concentration of "surface" and "bulk" chelate to be assessed. A detailed investigation of the effect of the system variables; pH, conditioning period, concentration, temperature, surface area and dispersing reagent on the rate of precipitation of the copper chelate species of general form, Cu(chel)2' was made. In addition the chemical nature of the adsorbed species and the structural form of the precipitates were determined with the aid of infra-red spectroscopy and the scanning electron microscope. On the basis of these results a model has been formulated for the adsorption processes. In this model the adsorption dissolution, is considered to occur in stages: 1. Oxide dissolution, 2. metal complex formation, 3. Metal chelate precipitation at the oxide surface and 4. “bulk” chelate formation by post-precipitation processes. The precipitation process was examined in more detail by the study of the adsorption of chelate on copper metal. The results of this study showed that it was possible to relate the structural type of precipitate formed, ie. fibrous or platelike, to the degree of supersaturation of the metal complex in solution. Furthermore, it was found that the precipitate structure determined whether it remained attached to the surface or detached. Contact angle measurements of air bubbles on copper metal conditioned with chelate were related to the adsorption results in an attempt to isolate the optimum conditions for flotation of oxide minerals.
- Full Text:
- Date Issued: 1986
- Authors: Bryson, Michael Andrew Walker
- Date: 1986
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:20969 , http://hdl.handle.net/10962/5729
- Description: This work constitutes a fundamental study of the interaction between chelating reagents and oxide minerals . The adsorption mechanisms have been elucidated for most of the systems generated by the oxides of copper(II) or iron(III) and chelating reagents octyl hydroxamate, N-phenylbenzohydroxamate, salicylaldoxime, 5-nitrosalicylaldoxime or 8-hydroxyquinoline. The results of the preliminary work on one of the systems, viz. the oxide-hydroxamate system, indicated that the classical type adsorption process, in which the reagent forms a uniform layer of chelate over the oxide surface was not applicable. Rather, the adsorption occurred via the formation of a discrete metal-chelate precipitate at the oxide surface. In order to better understand the associated with copper (II) oxide, adsorption process the oxide was recrystallized to produce a coarser material with a more uniform surface. This allowed the oxide surface to be viewed under the scanning electron microscope and also enabled the relative concentration of "surface" and "bulk" chelate to be assessed. A detailed investigation of the effect of the system variables; pH, conditioning period, concentration, temperature, surface area and dispersing reagent on the rate of precipitation of the copper chelate species of general form, Cu(chel)2' was made. In addition the chemical nature of the adsorbed species and the structural form of the precipitates were determined with the aid of infra-red spectroscopy and the scanning electron microscope. On the basis of these results a model has been formulated for the adsorption processes. In this model the adsorption dissolution, is considered to occur in stages: 1. Oxide dissolution, 2. metal complex formation, 3. Metal chelate precipitation at the oxide surface and 4. “bulk” chelate formation by post-precipitation processes. The precipitation process was examined in more detail by the study of the adsorption of chelate on copper metal. The results of this study showed that it was possible to relate the structural type of precipitate formed, ie. fibrous or platelike, to the degree of supersaturation of the metal complex in solution. Furthermore, it was found that the precipitate structure determined whether it remained attached to the surface or detached. Contact angle measurements of air bubbles on copper metal conditioned with chelate were related to the adsorption results in an attempt to isolate the optimum conditions for flotation of oxide minerals.
- Full Text:
- Date Issued: 1986
Analytical procedures for the determination of wattle polyphenols in wastewaters
- Authors: Hendry, Antony John
- Date: 1984
- Subjects: Liquid chromatography , Spectrophotometry , High performance liquid chromatography , Water -- Purification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4431 , http://hdl.handle.net/10962/d1007221 , Liquid chromatography , Spectrophotometry , High performance liquid chromatography , Water -- Purification
- Full Text:
- Date Issued: 1984
- Authors: Hendry, Antony John
- Date: 1984
- Subjects: Liquid chromatography , Spectrophotometry , High performance liquid chromatography , Water -- Purification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4431 , http://hdl.handle.net/10962/d1007221 , Liquid chromatography , Spectrophotometry , High performance liquid chromatography , Water -- Purification
- Full Text:
- Date Issued: 1984
The synthesis and properties of some polymer hydrogels
- Authors: Hird, Bryn
- Date: 1984 , 2013-04-05
- Subjects: Colloids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4428 , http://hdl.handle.net/10962/d1006975 , Colloids
- Description: The interactions between water molecules and polyelectrolyte species in aqueous solutions are reviewed and are used to infer interactions occuring in swollen crosslinked polyelectrolyte hydrogels. Linear poly(acrylic acid ) and derivatives neutralised to varying degrees with alkali-metal hydroxides are prepared and characterised. Samples of these compounds are crosslinked by 'Y - irradiation to form hydrogels. Hydration studies on linear polymers, crosslinked material and a commercial polyacrylate hydrogel indicate a possible hydration structure and provide some insight into the nature of water-polymer interactions within a sHollen polyacrylate gel. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1984
- Authors: Hird, Bryn
- Date: 1984 , 2013-04-05
- Subjects: Colloids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4428 , http://hdl.handle.net/10962/d1006975 , Colloids
- Description: The interactions between water molecules and polyelectrolyte species in aqueous solutions are reviewed and are used to infer interactions occuring in swollen crosslinked polyelectrolyte hydrogels. Linear poly(acrylic acid ) and derivatives neutralised to varying degrees with alkali-metal hydroxides are prepared and characterised. Samples of these compounds are crosslinked by 'Y - irradiation to form hydrogels. Hydration studies on linear polymers, crosslinked material and a commercial polyacrylate hydrogel indicate a possible hydration structure and provide some insight into the nature of water-polymer interactions within a sHollen polyacrylate gel. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1984
Continuous-flow dynamic dialysis and its application to collagen-ligand interactions
- Authors: Sparrow, Neil Arthur
- Date: 1983
- Subjects: Collagen Ligands (Biochemistry) Ligand binding (Biochemistry) Protein-protein interactions Tannins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4297 , http://hdl.handle.net/10962/d1004617
- Description: Studies undertaken to investigate the binding of low molecular mass analogues of polyphenolic vegetable tannins to collagen have prompted the development of a new method to investigate protein-ligand interactions. This method, the continuous-flow dynamic dialysis method (CFDD), differs from conventional dialysis procedures used for protein-ligand binding studies. In this method, the ligand concentration in the diffusate is monitored automatically at successive closely spaced time intervals while being continuously eluted from the dialysis cell. The primary data obtained by this method consists of a series of spectrophotometric absorbance measurements representing the ligand concentration in the sink compartment of a dialysis cell. This primary data is recorded by means of a data logging device onto a punched paper tape for subsequent computer processing. Two original methods are presented for analysing the primary data to extract the protein-ligand binding isotherm. The first of these is a direct analysis which relies on Fick's first law of diffusion. In this method it is necessary to establish, by means of a control experiment, a value for the ligand permeation constant. This is used in a subsequent analysis to establish a relationship between the measured rate of diffusion of the ligand from a protein-ligand mixture and the concentration of unbound ligand which is in equilibrium with the protein-ligand complex. The protein-ligand binding isotherm is obtained from parametric equations which give the quantity of ligand bound to the protein and the concentration of unbound ligand in the sample compartment as functions of time. The second method, which is more general, utilizes the same primary data but is based on establishing a system transfer function to characterise the dialysis and eluting processes. This analysis depends on the linearity of the system and utilizes numerical laplace transforms of the primary data sets obtained from control and protein-ligand dialyses. Laplace transforms are used to effect a deconvolution of the transfer function from the primary data and yield the concentration of ligand in equilibrium with the protein-ligand complex. This procedure yields, simultaneously, both the total ligand concentration and the concentration of unbound ligand in the protein compartment of the dialysis cell. These quantities are used to establish the binding isotherm for the protein ligand system. Numerical inversion of the laplace transforms in this analysis is effected by their reduction to Fourier series. The experimental reliability of the continuous-flow dynamic dialysis method, and validity of the two analytical methods used to derive a binding isotherm from dialysis data are evaluated from studies of the binding of phenol red to bovine serum albumin (BSA) at 15⁰, 20⁰ and 25⁰ C, as well as from simulated binding curves generated by the numerical solution of the differential equations used to describe the dialysis and elution process in terms of a two-site Scatchard binding model. The method is used to investigate the binding to collagen of a series of low molecular mass phenolic compounds which can be isolated from Wattle and Quebracho vegetable tannin extracts. These compounds can be considered as monomeric precursor analogues of the polymeric vegetable tannins. The binding of these ligands to collagen is shown to be characterised by high capacity, low affinity binding in which the uptake of ligand by the protein increases linearly with increasing ligand concentration. Collagen exhibits no indication of site saturation for these ligands over the experimentally accessible concentration ranges investigated.
- Full Text:
- Date Issued: 1983
- Authors: Sparrow, Neil Arthur
- Date: 1983
- Subjects: Collagen Ligands (Biochemistry) Ligand binding (Biochemistry) Protein-protein interactions Tannins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4297 , http://hdl.handle.net/10962/d1004617
- Description: Studies undertaken to investigate the binding of low molecular mass analogues of polyphenolic vegetable tannins to collagen have prompted the development of a new method to investigate protein-ligand interactions. This method, the continuous-flow dynamic dialysis method (CFDD), differs from conventional dialysis procedures used for protein-ligand binding studies. In this method, the ligand concentration in the diffusate is monitored automatically at successive closely spaced time intervals while being continuously eluted from the dialysis cell. The primary data obtained by this method consists of a series of spectrophotometric absorbance measurements representing the ligand concentration in the sink compartment of a dialysis cell. This primary data is recorded by means of a data logging device onto a punched paper tape for subsequent computer processing. Two original methods are presented for analysing the primary data to extract the protein-ligand binding isotherm. The first of these is a direct analysis which relies on Fick's first law of diffusion. In this method it is necessary to establish, by means of a control experiment, a value for the ligand permeation constant. This is used in a subsequent analysis to establish a relationship between the measured rate of diffusion of the ligand from a protein-ligand mixture and the concentration of unbound ligand which is in equilibrium with the protein-ligand complex. The protein-ligand binding isotherm is obtained from parametric equations which give the quantity of ligand bound to the protein and the concentration of unbound ligand in the sample compartment as functions of time. The second method, which is more general, utilizes the same primary data but is based on establishing a system transfer function to characterise the dialysis and eluting processes. This analysis depends on the linearity of the system and utilizes numerical laplace transforms of the primary data sets obtained from control and protein-ligand dialyses. Laplace transforms are used to effect a deconvolution of the transfer function from the primary data and yield the concentration of ligand in equilibrium with the protein-ligand complex. This procedure yields, simultaneously, both the total ligand concentration and the concentration of unbound ligand in the protein compartment of the dialysis cell. These quantities are used to establish the binding isotherm for the protein ligand system. Numerical inversion of the laplace transforms in this analysis is effected by their reduction to Fourier series. The experimental reliability of the continuous-flow dynamic dialysis method, and validity of the two analytical methods used to derive a binding isotherm from dialysis data are evaluated from studies of the binding of phenol red to bovine serum albumin (BSA) at 15⁰, 20⁰ and 25⁰ C, as well as from simulated binding curves generated by the numerical solution of the differential equations used to describe the dialysis and elution process in terms of a two-site Scatchard binding model. The method is used to investigate the binding to collagen of a series of low molecular mass phenolic compounds which can be isolated from Wattle and Quebracho vegetable tannin extracts. These compounds can be considered as monomeric precursor analogues of the polymeric vegetable tannins. The binding of these ligands to collagen is shown to be characterised by high capacity, low affinity binding in which the uptake of ligand by the protein increases linearly with increasing ligand concentration. Collagen exhibits no indication of site saturation for these ligands over the experimentally accessible concentration ranges investigated.
- Full Text:
- Date Issued: 1983
The thermodynamics of binary liquid mixtures
- Scoones, Brett Warren Hamilton
- Authors: Scoones, Brett Warren Hamilton
- Date: 1983 , 2013-03-15
- Subjects: Thermodynamics , Thermodynamics -- Tables , Solution (Chemistry) , Liquids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4392 , http://hdl.handle.net/10962/d1005893 , Thermodynamics , Thermodynamics -- Tables , Solution (Chemistry) , Liquids
- Description: A systematic study of the excess thermodynamic properties of two-ring compounds and n-alkanes was conducted. The excess enthalpies were determined at 288,15 K and 298,15 K by using a flow microcalorimetric technique. The excess volumes of tetralin and cycloalkanes, and tetralin and --alkans at 288,15 K and 298,15 K were determined by using a vibrating tube densitometer. The results showed trends relating to the size and shape of the n-alkane and cycloalkan molecules. The theory developed by Flory was applied to the decalin + cycloalkane and + n-alkane systems and this gave qualitative predictions of the excess enthalpies from the excess volumes and vice versa. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1983
- Authors: Scoones, Brett Warren Hamilton
- Date: 1983 , 2013-03-15
- Subjects: Thermodynamics , Thermodynamics -- Tables , Solution (Chemistry) , Liquids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4392 , http://hdl.handle.net/10962/d1005893 , Thermodynamics , Thermodynamics -- Tables , Solution (Chemistry) , Liquids
- Description: A systematic study of the excess thermodynamic properties of two-ring compounds and n-alkanes was conducted. The excess enthalpies were determined at 288,15 K and 298,15 K by using a flow microcalorimetric technique. The excess volumes of tetralin and cycloalkanes, and tetralin and --alkans at 288,15 K and 298,15 K were determined by using a vibrating tube densitometer. The results showed trends relating to the size and shape of the n-alkane and cycloalkan molecules. The theory developed by Flory was applied to the decalin + cycloalkane and + n-alkane systems and this gave qualitative predictions of the excess enthalpies from the excess volumes and vice versa. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1983
Separation and characterisation of chromium (III) carboxylate solutions
- Bryson, Michael Andrew Walker
- Authors: Bryson, Michael Andrew Walker
- Date: 1981
- Subjects: Chromium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4416 , http://hdl.handle.net/10962/d1006847
- Description: From Summary: The complexes present in chromium(III) carboxylate solutions (acetate or formate) were separated using ion exchange chromatography, electrophoresis and gel filtration. Eight cationic species and one non-ionic species with charges from 0 to +3 and nuclearities ranging from mononuclear to quadranuclear were isolated from chromium(III) acetate solutions. Six cationic species with charges from +1 to +3 and nuclearities ranging from mononuclear to trinuclear were isolated from chromium(III) formate solutions. The empirical formulae for these complexes were determined by analytical methods. Infra- red spectroscopy was used to distinguish between monodentate and bidentate bridged carboxylate ligands. An immediate change in the visible spectrum of a complex on its acidification was used as evidence that a terminal hydroxo group was present.
- Full Text:
- Date Issued: 1981
- Authors: Bryson, Michael Andrew Walker
- Date: 1981
- Subjects: Chromium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4416 , http://hdl.handle.net/10962/d1006847
- Description: From Summary: The complexes present in chromium(III) carboxylate solutions (acetate or formate) were separated using ion exchange chromatography, electrophoresis and gel filtration. Eight cationic species and one non-ionic species with charges from 0 to +3 and nuclearities ranging from mononuclear to quadranuclear were isolated from chromium(III) acetate solutions. Six cationic species with charges from +1 to +3 and nuclearities ranging from mononuclear to trinuclear were isolated from chromium(III) formate solutions. The empirical formulae for these complexes were determined by analytical methods. Infra- red spectroscopy was used to distinguish between monodentate and bidentate bridged carboxylate ligands. An immediate change in the visible spectrum of a complex on its acidification was used as evidence that a terminal hydroxo group was present.
- Full Text:
- Date Issued: 1981
The study of hydroxyoximes and hydroxamic acids supported on macroporous resins and their use in the rapid seperation of metals
- Authors: Hemmes, Marlene
- Date: 1979
- Subjects: Chromatographic analysis , Separation (Technology) , Metal ions , Solvent extraction , Extraction (Chemistry) , Oximes , Metals -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4453 , http://hdl.handle.net/10962/d1009512
- Description: Introduction: The macroporous Amberlite XAD resins were coated with LIX-64N and examined for the rate of uptake of copper . XAD-7 was by far the best support and gave a satisfactory rate of uptake up to loadings of 60% (w/w). The specific surface area of XAD-7 was measured by the adsorption of methylene blue from aqueous solution. The area of the wetted resin was five times less than that of the dry resin. LIX-65N was purified and the anti isomer characterised using spectroscopic techniques . The rate of uptake of copper was not improved by use of purified LIX-65N or by addition of LIX-63. XAD-7 coated with LIX-65N was used in columns. Elution curves for copper showed negligible tailing, and rapid separations of copper from iron (111), nickel, cobalt and magnesium by selective absorption were achieved. Copper was concentrated from very dilute solution at a flow rate of 50 ml min -1 ,and a 99% recovery was obtained. The method was applied to the rapid determination of copper in brass and bronze. A series of long-chain hydroxamic acids were synthesised and tested for suitability as stationary phase on XAD-7. Oleohydroxamic acid and naphthenohydroxamic acid were the most promising. The r ate of uptake of copper was reduced by the use of nonylphenol or amyl alcohol as a diluent. The capacities for copper of the hydroxamic acids were less when supported on XAD-7 than when used as liquid ionexchangers. The distribution coefficients of cobalt, nickel, zinc, lead, vanadium, uranium, iron (111) and copper were measured as a function of pH. XAD-7 coated with oleohydroxamic acid was used in columns for the rapid separation of iron (111) from copper and of copper from nickel, cobalt, lead and zinc. Copper was concentrated from very dilute solution at a flow rate of 45 ml min -1 and a 100,8% recovery was obtained. Copper was successfully separated from nickel by selective elution. The elution curves obtained show negligible tailing. The resin loaded with oleohydroxamic acid lost capacity due to chemical instability. Naphthenohydroxamic acid supported on XAD-7 was not suitable for use in columns, because it was physically unstable.
- Full Text:
- Date Issued: 1979
- Authors: Hemmes, Marlene
- Date: 1979
- Subjects: Chromatographic analysis , Separation (Technology) , Metal ions , Solvent extraction , Extraction (Chemistry) , Oximes , Metals -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4453 , http://hdl.handle.net/10962/d1009512
- Description: Introduction: The macroporous Amberlite XAD resins were coated with LIX-64N and examined for the rate of uptake of copper . XAD-7 was by far the best support and gave a satisfactory rate of uptake up to loadings of 60% (w/w). The specific surface area of XAD-7 was measured by the adsorption of methylene blue from aqueous solution. The area of the wetted resin was five times less than that of the dry resin. LIX-65N was purified and the anti isomer characterised using spectroscopic techniques . The rate of uptake of copper was not improved by use of purified LIX-65N or by addition of LIX-63. XAD-7 coated with LIX-65N was used in columns. Elution curves for copper showed negligible tailing, and rapid separations of copper from iron (111), nickel, cobalt and magnesium by selective absorption were achieved. Copper was concentrated from very dilute solution at a flow rate of 50 ml min -1 ,and a 99% recovery was obtained. The method was applied to the rapid determination of copper in brass and bronze. A series of long-chain hydroxamic acids were synthesised and tested for suitability as stationary phase on XAD-7. Oleohydroxamic acid and naphthenohydroxamic acid were the most promising. The r ate of uptake of copper was reduced by the use of nonylphenol or amyl alcohol as a diluent. The capacities for copper of the hydroxamic acids were less when supported on XAD-7 than when used as liquid ionexchangers. The distribution coefficients of cobalt, nickel, zinc, lead, vanadium, uranium, iron (111) and copper were measured as a function of pH. XAD-7 coated with oleohydroxamic acid was used in columns for the rapid separation of iron (111) from copper and of copper from nickel, cobalt, lead and zinc. Copper was concentrated from very dilute solution at a flow rate of 45 ml min -1 and a 100,8% recovery was obtained. Copper was successfully separated from nickel by selective elution. The elution curves obtained show negligible tailing. The resin loaded with oleohydroxamic acid lost capacity due to chemical instability. Naphthenohydroxamic acid supported on XAD-7 was not suitable for use in columns, because it was physically unstable.
- Full Text:
- Date Issued: 1979
The polysaccharides of Opuntia ficus-indica (L.) Mill. and Opuntia aurantiaca Lindl.
- Authors: McGarvie, Donald
- Date: 1977
- Subjects: Polysaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4438 , http://hdl.handle.net/10962/d1007597
- Description: The partially acetylated acidic mucilage isolated from the cactus Opuntia ficus-indica consists of a highly branched molecule containing D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 2.9:6.6:3.8:1.3 : 1.0. A partial hydrolysis study led to the isolation of fourteen oligosaccharides and a degraded polysaccharide. Periodate oxidation of the degraded polysaccharide and methylation analysis of the degraded and reduced degraded polysaccharides led to the proposal of a structure for the degraded polysaccharide consisting of a chain of alternating α-l,4-D-galactopyranosyluronic acid and β-1,2-Lrhamnopyranosyl units with branches consisting of short chains of β-1,6-D-galactopyranosyl units Iinked to C-3 of the rhamnose residues. An insight into the nature of the peripheral side-chains was obtained by methylation studies of the oligosaccharides and the native polysaccharide. The majority of the side-chains are terminated by D-xylopyranosyl and L-arabinofuranosyl units while there is a small proportion of D-galactopyranosyl end-groups. The remaining units of the peripheral chains consists of mainly 1,3- and 1,5-1 inked L-arabinofuranosyl units. The acidic polysaccharide isolated from the jointed cactus Opuntia aurantiaca contains D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 5.9:5 .5:3.4: 1. 2:1.0 . A partial hydrolysis study revealed a similar series of galactose containing oligosaccharides as was identified from the mucilage of Opuntia ficus-indica. The degraded polysaccharide isolated from the partial hydrolysate was methylated and a possible structure proposed for the repeating unit. Methylation studies of the native polysaccharide indicated a polysaccharide with a more complex structure than that for the mucilage of Opuntia ficus-indica.
- Full Text:
- Date Issued: 1977
- Authors: McGarvie, Donald
- Date: 1977
- Subjects: Polysaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4438 , http://hdl.handle.net/10962/d1007597
- Description: The partially acetylated acidic mucilage isolated from the cactus Opuntia ficus-indica consists of a highly branched molecule containing D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 2.9:6.6:3.8:1.3 : 1.0. A partial hydrolysis study led to the isolation of fourteen oligosaccharides and a degraded polysaccharide. Periodate oxidation of the degraded polysaccharide and methylation analysis of the degraded and reduced degraded polysaccharides led to the proposal of a structure for the degraded polysaccharide consisting of a chain of alternating α-l,4-D-galactopyranosyluronic acid and β-1,2-Lrhamnopyranosyl units with branches consisting of short chains of β-1,6-D-galactopyranosyl units Iinked to C-3 of the rhamnose residues. An insight into the nature of the peripheral side-chains was obtained by methylation studies of the oligosaccharides and the native polysaccharide. The majority of the side-chains are terminated by D-xylopyranosyl and L-arabinofuranosyl units while there is a small proportion of D-galactopyranosyl end-groups. The remaining units of the peripheral chains consists of mainly 1,3- and 1,5-1 inked L-arabinofuranosyl units. The acidic polysaccharide isolated from the jointed cactus Opuntia aurantiaca contains D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 5.9:5 .5:3.4: 1. 2:1.0 . A partial hydrolysis study revealed a similar series of galactose containing oligosaccharides as was identified from the mucilage of Opuntia ficus-indica. The degraded polysaccharide isolated from the partial hydrolysate was methylated and a possible structure proposed for the repeating unit. Methylation studies of the native polysaccharide indicated a polysaccharide with a more complex structure than that for the mucilage of Opuntia ficus-indica.
- Full Text:
- Date Issued: 1977
A study of factors affecting precision in atomic absorption spectrometry
- Roos, Johannes Tielman Hofmeyr
- Authors: Roos, Johannes Tielman Hofmeyr
- Date: 1976
- Subjects: Atomic absorption spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4490 , http://hdl.handle.net/10962/d1013080
- Description: 1. The effect of deviations from Beer's law on the precision of atomic absorption analysis has been examined from a theoretical point of view, and a function has been derived which makes it possible to evaluate quantitatively the effect of calibration curvature on the precision of analysis. The influence of incomplete sample volatilization on calibration curvature has been briefly investigated. 2. Possible error sources in atomic absorption spectrometry have been classified according to the "error function" (i.e., the dependence, upon transmittance T, of the uncertainty dT in a given transmittance measurement) with which they are associated. The magnitude of the contribution from each component function to the overall error function has been evaluated quantitatively, and it has been shown that the major component in nearly every case examined is that associated with the dynamic nature of the flame. Concentration ranges for optimum precision are suggested. 3. The effect of varying instrumental parameters on precision has been investigated, and generalized conditions for best precision have been ascertained. 4. The effect of an initial solvent extraction step on the precision of atomic absorption has been investigated for the elements copper and lead. It is shown that solvent extraction may be used to improve both the analytical sensitivity and the precision of analysis when very low concentrations of metal are determined. 5. The precision of analytical methods involving atomic absorption spectrometry has been studied, and the standard deviations compared with those obtained for the analysis of similar samples by means of a variety of other methods of analysis, both instrumental and classical.
- Full Text:
- Date Issued: 1976
- Authors: Roos, Johannes Tielman Hofmeyr
- Date: 1976
- Subjects: Atomic absorption spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4490 , http://hdl.handle.net/10962/d1013080
- Description: 1. The effect of deviations from Beer's law on the precision of atomic absorption analysis has been examined from a theoretical point of view, and a function has been derived which makes it possible to evaluate quantitatively the effect of calibration curvature on the precision of analysis. The influence of incomplete sample volatilization on calibration curvature has been briefly investigated. 2. Possible error sources in atomic absorption spectrometry have been classified according to the "error function" (i.e., the dependence, upon transmittance T, of the uncertainty dT in a given transmittance measurement) with which they are associated. The magnitude of the contribution from each component function to the overall error function has been evaluated quantitatively, and it has been shown that the major component in nearly every case examined is that associated with the dynamic nature of the flame. Concentration ranges for optimum precision are suggested. 3. The effect of varying instrumental parameters on precision has been investigated, and generalized conditions for best precision have been ascertained. 4. The effect of an initial solvent extraction step on the precision of atomic absorption has been investigated for the elements copper and lead. It is shown that solvent extraction may be used to improve both the analytical sensitivity and the precision of analysis when very low concentrations of metal are determined. 5. The precision of analytical methods involving atomic absorption spectrometry has been studied, and the standard deviations compared with those obtained for the analysis of similar samples by means of a variety of other methods of analysis, both instrumental and classical.
- Full Text:
- Date Issued: 1976
A dielectric and spectroscopic study of molecular association in solutions of alcohols
- Authors: Campbell, Colin
- Date: 1975
- Subjects: Alcohols , Dielectrics , Spectrum analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4454 , http://hdl.handle.net/10962/d1010424
- Description: This study is concerned with the association characteristics of solutions of alcohols in some non-polar solvents. The permittivities at 2 MHz and 25°C for solutions of the straight chain octanols in cyclohexane, carbon tetrachloride and benzene have been examined over the entire solute concentration range, with particular attention -1 being paid to the range below 0.1 molℓ⁻¹ By applying the Kirkwood- Fröhlich equation to these data, the apparent dipole moments of the alcohols as a function of concentration have been evaluated. These concentration dependencies have been correlated with infrared absorption results on the same systems to provide information on the sizes and configurations of the proposed hydrogen bonded multimers. It is concluded that, at very low solute concentrations, the alcohol molecules exist as monomers; but with increasing concentration, two types of hydrogen bonded multimers are formed, the first (at low concentrations) being of high dipole moment and the second (at higher concentrations) being of low dipole moment. At high concentrations, the molecules associate to form a three-dimensional network. Attempts have been made to determine equilibrium parameters for molecular models which are consistent with the qualitative understanding of the association behaviour. These parameters were obtained by applying least-squares, curve-fitting techniques to the low concentration permittivity data. A similar investigation has been conducted on solutions of 2,3,4-trimethyl-3-pentanol in the same solvents. The steric hindrance around the hydroxyl group of this alcohol modifies the association behaviour so that a three-dimensional network does not form at high solute concentrations. Proton magnetic resonance chemical shifts for the hydroxyl proton of this alcohol in carbon tetrachloride solutions have been measured. Attempts have also been made to determine equilibrium parameters which describe formation of the hydrogen bonded multimers. To extend this study to include solutes other than octanols, similar experiments have been conducted on solutions of t-butanol in hexadecane, a system which has recently been investigated by other workers using different experimental techniques. The association behaviour of this system is qualitatively similar to that of the straight-chain octanols. The combination of permittivity and infrared measurements, although proving extremely powerful in interpreting the association characteristics of dilute alcohol solutions, is less adequate at high solute concentrations. Attention was therefore directed towards dielectric relaxation and viscosity studies to investigate concentrated solutions. The relaxation times at 20°C of the low frequency dispersion have been measured for solutions of 1-propanol, 1-butanol, 1-hexanol, 1-octanol and 1-decanol in cyclohexane using time domain reflectometry techniques. Similar measurements have also been made on solutions of 1-butanol and 1-octanol in carbon tetrachloride and in benzene. The concentration dependence of the viscosities of certain of these systems has also been examined in an independent study. The ratio of the dielectric relaxation time to the viscosity, the "reduced relaxation time", is qualitatively similar for each system studied. This similarity leads to an explanation of the molecular process responsible for the low frequency dispersion in terms of the proximity of the hydroxyl groups in concentrated alcohol solutions and the fraction of the groups which are not involved in hydrogen bonding.
- Full Text:
- Date Issued: 1975
- Authors: Campbell, Colin
- Date: 1975
- Subjects: Alcohols , Dielectrics , Spectrum analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4454 , http://hdl.handle.net/10962/d1010424
- Description: This study is concerned with the association characteristics of solutions of alcohols in some non-polar solvents. The permittivities at 2 MHz and 25°C for solutions of the straight chain octanols in cyclohexane, carbon tetrachloride and benzene have been examined over the entire solute concentration range, with particular attention -1 being paid to the range below 0.1 molℓ⁻¹ By applying the Kirkwood- Fröhlich equation to these data, the apparent dipole moments of the alcohols as a function of concentration have been evaluated. These concentration dependencies have been correlated with infrared absorption results on the same systems to provide information on the sizes and configurations of the proposed hydrogen bonded multimers. It is concluded that, at very low solute concentrations, the alcohol molecules exist as monomers; but with increasing concentration, two types of hydrogen bonded multimers are formed, the first (at low concentrations) being of high dipole moment and the second (at higher concentrations) being of low dipole moment. At high concentrations, the molecules associate to form a three-dimensional network. Attempts have been made to determine equilibrium parameters for molecular models which are consistent with the qualitative understanding of the association behaviour. These parameters were obtained by applying least-squares, curve-fitting techniques to the low concentration permittivity data. A similar investigation has been conducted on solutions of 2,3,4-trimethyl-3-pentanol in the same solvents. The steric hindrance around the hydroxyl group of this alcohol modifies the association behaviour so that a three-dimensional network does not form at high solute concentrations. Proton magnetic resonance chemical shifts for the hydroxyl proton of this alcohol in carbon tetrachloride solutions have been measured. Attempts have also been made to determine equilibrium parameters which describe formation of the hydrogen bonded multimers. To extend this study to include solutes other than octanols, similar experiments have been conducted on solutions of t-butanol in hexadecane, a system which has recently been investigated by other workers using different experimental techniques. The association behaviour of this system is qualitatively similar to that of the straight-chain octanols. The combination of permittivity and infrared measurements, although proving extremely powerful in interpreting the association characteristics of dilute alcohol solutions, is less adequate at high solute concentrations. Attention was therefore directed towards dielectric relaxation and viscosity studies to investigate concentrated solutions. The relaxation times at 20°C of the low frequency dispersion have been measured for solutions of 1-propanol, 1-butanol, 1-hexanol, 1-octanol and 1-decanol in cyclohexane using time domain reflectometry techniques. Similar measurements have also been made on solutions of 1-butanol and 1-octanol in carbon tetrachloride and in benzene. The concentration dependence of the viscosities of certain of these systems has also been examined in an independent study. The ratio of the dielectric relaxation time to the viscosity, the "reduced relaxation time", is qualitatively similar for each system studied. This similarity leads to an explanation of the molecular process responsible for the low frequency dispersion in terms of the proximity of the hydroxyl groups in concentrated alcohol solutions and the fraction of the groups which are not involved in hydrogen bonding.
- Full Text:
- Date Issued: 1975