Assessment of the host potential of TETROL [(+)-(2R,3R)-1,1,4,4- tetraphenylbutane-1,2,3,4-TETROL] for the separation of isomers and related compounds
- Authors: Dorfling, Sasha-Lee
- Date: 2018
- Subjects: Chemistry, Organic , Thermal analysis Hydrogen bonding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/22060 , vital:29817
- Description: In this study, we investigated the potential of a host compound, (+)-(2R,3R)-1,1,4,4- tetraphenylbutane-1,2,3,4-tetrol (TETROL), for use in the separation of isomers and related compounds using host-guest chemistry. The synthesis of this host was carried out using a standard Grignard procedure, reacting naturally-occurring optically active tartaric acid with phenylmagnesium bromide. The feasibility of this host for separating isomers and structurally-related compounds was investigated by recrystallizing it from various potential cyclic, aromatic and aliphatic guest compounds. The extent of host inclusion and guest separation were determined using 1H-NMR spectroscopy and GCMS analyses. Competition studies were conducted to establish the selectivity of TETROL for the various guest species and whether this host would be able to discriminate between them. In this instance, the host was recrystallized from equimolar amounts of binary, ternary, quaternary or quinary mixtures of the guests present in each target study. Subsequent binary or ternary competitions were conducted where the molar ratios of the guest species were varied beyond equimolar, and the guest selectivity of TETROL thus evaluated by means of selectivity profiles. Further analyses included single crystal X-ray diffraction (SCXRD), thermal analysis and Hirshfeld surface analysis. Any crystalline inclusion complex formed between host and guest, with suitable crystal quality, was analysed using SCXRD in order to determine the nature of any significant host–guest interactions present. Thermogravimetric and differential scanning calorimetry experiments provided further insight into complex stability by analysing the thermal events experienced by the complexes as they were heated at 10 °C/min. The data obtained from Hirshfeld surface analyses were used to determine whether host selectivity and/or thermal stability of the complexes were related to the number and types of interactions, observed from SCXRD, between host and guest. The ability of TETROL to discriminate between related compounds was favourable. This host proved to have selective preference for aniline over its methylated derivatives, N-methylaniline and N,N-dimethylaniline. It was also selective for cyclohexylamine over cyclohexanol and cyclohexanone, and discriminated against the pyridine, piperidine and dioxane heterocyclics in favour of morpholine. Furthermore, this host was successful in the selective separation of isomers; for example, it selectively showed discrimination between the three toluidine isomers (p-toluidine > m-toluidine > o-toluidine) and the cresols (p-cresol > m-cresol > o-cresol). Each guest mixture was selected based on data from experiments using either the industrial significance of its separation or because the mixture would add to the knowledge base of the host compound’s preferences and selectivities. In a separate study, TETROL and its derivative, (–)-(2R,3R)-2,3-dimethoxy-1,1,4,4- tetraphenylbutane-1,4-diol (DMT), were also allowed to compete for the inclusion of the guest cyclohexanone, where TETROL demonstrated superior ability. This host, in addition, showed potential for the separation of cis- and trans- 2-methylcyclohexanol.
- Full Text:
- Date Issued: 2018
- Authors: Dorfling, Sasha-Lee
- Date: 2018
- Subjects: Chemistry, Organic , Thermal analysis Hydrogen bonding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/22060 , vital:29817
- Description: In this study, we investigated the potential of a host compound, (+)-(2R,3R)-1,1,4,4- tetraphenylbutane-1,2,3,4-tetrol (TETROL), for use in the separation of isomers and related compounds using host-guest chemistry. The synthesis of this host was carried out using a standard Grignard procedure, reacting naturally-occurring optically active tartaric acid with phenylmagnesium bromide. The feasibility of this host for separating isomers and structurally-related compounds was investigated by recrystallizing it from various potential cyclic, aromatic and aliphatic guest compounds. The extent of host inclusion and guest separation were determined using 1H-NMR spectroscopy and GCMS analyses. Competition studies were conducted to establish the selectivity of TETROL for the various guest species and whether this host would be able to discriminate between them. In this instance, the host was recrystallized from equimolar amounts of binary, ternary, quaternary or quinary mixtures of the guests present in each target study. Subsequent binary or ternary competitions were conducted where the molar ratios of the guest species were varied beyond equimolar, and the guest selectivity of TETROL thus evaluated by means of selectivity profiles. Further analyses included single crystal X-ray diffraction (SCXRD), thermal analysis and Hirshfeld surface analysis. Any crystalline inclusion complex formed between host and guest, with suitable crystal quality, was analysed using SCXRD in order to determine the nature of any significant host–guest interactions present. Thermogravimetric and differential scanning calorimetry experiments provided further insight into complex stability by analysing the thermal events experienced by the complexes as they were heated at 10 °C/min. The data obtained from Hirshfeld surface analyses were used to determine whether host selectivity and/or thermal stability of the complexes were related to the number and types of interactions, observed from SCXRD, between host and guest. The ability of TETROL to discriminate between related compounds was favourable. This host proved to have selective preference for aniline over its methylated derivatives, N-methylaniline and N,N-dimethylaniline. It was also selective for cyclohexylamine over cyclohexanol and cyclohexanone, and discriminated against the pyridine, piperidine and dioxane heterocyclics in favour of morpholine. Furthermore, this host was successful in the selective separation of isomers; for example, it selectively showed discrimination between the three toluidine isomers (p-toluidine > m-toluidine > o-toluidine) and the cresols (p-cresol > m-cresol > o-cresol). Each guest mixture was selected based on data from experiments using either the industrial significance of its separation or because the mixture would add to the knowledge base of the host compound’s preferences and selectivities. In a separate study, TETROL and its derivative, (–)-(2R,3R)-2,3-dimethoxy-1,1,4,4- tetraphenylbutane-1,4-diol (DMT), were also allowed to compete for the inclusion of the guest cyclohexanone, where TETROL demonstrated superior ability. This host, in addition, showed potential for the separation of cis- and trans- 2-methylcyclohexanol.
- Full Text:
- Date Issued: 2018
Investigation of the potential separation of isomers and related compounds using host compound (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol
- Authors: Pohl, Pieter Lourens
- Date: 2018
- Subjects: Chemistry, Organic , Clathrate compounds Thermal analysis
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23131 , vital:30432
- Description: In this study, we investigated the potential of a host compound, (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT), for use in the separation of isomers and related compounds using host-guest chemistry. The title molecule, DMT, is composed of a butane chain bearing hydroxyl moieties on the terminal carbons and methoxy moieties on the two internal, chiral carbon atoms. In addition, there are two phenyl rings on each of the terminal carbons. The synthesis of DMT was carried out by subjecting the diester of naturally-occurring optically active tartaric acid to a Grignard reaction employing phenylmagnesium bromide. Subsequent methylation of the secondary hydroxy groups with dimethyl sulfate afforded DMT. The resulting host molecule was investigated for its inclusion abilities by crystallizing with a number of potential aromatic, aliphatic and alicyclic guests such as toluene, aniline, nitrobenzene, anisole, cyclohexane, ethyl acetate and ethanol. Host:guest ratios were determined by means of 1H-NMR spectroscopy. Of the hosts investigated, DMT favoured a host:guest ratio of 2:1 for all included guests investigated. It complexed with most non-polycyclic aromatic guests as well as cyclohexane, cyclohexene and cyclohexanone. It was not able to include short chain or branched alcohols such as methanol, ethanol or 2-propanol, or other hetero-aliphatic or hetero- cyclic compounds such as diethyl ether, acetonitrile, morpholine or dioxane. Competition inclusion experiments were performed in which DMT was crystallized from equimolar and non-equimolar binary, ternary and quaternary mixtures of appropriate guests. The mother liquor mixtures and resultant crystals were subjected to GC-MS analysis in order to determine whether DMT showed discriminatory behaviour towards the guests from a mixture. It was observed that DMT was able to differentiate between related compounds, for example, the host preferred to include N,N-dimethylaniline compared with N-methylaniline and aniline. The host also discriminated against isomers, for example, p-xylene was preferentially included over o-xylene and m-xylene, while o-cresol was included in preference to p-cresol and m-cresol. Single crystal X-ray analysis was used to investigate the host–guest interactions responsible for guest inclusion, as well as to discern reasons for the host’s selective behaviour. X-ray data for the inclusion complexes indicated that each complex was isostructural, crystallizing in the monoclinic C2 crystal system. A pair of 1,3- and 2,4- intramolecular hydrogen bonds, as well as intramolecular non-classic hydrogen bonds between adjacent ortho-aromatic hydrogens and hydroxy moieties was a significant stabilizing factor for the geometry of the host. Guests were held within discrete cavities in the crystal lattice, and experienced only π–π stacking, CH–π interactions and other short contacts. Thermal analyses were used to determine the relative thermal stabilities of the complexes, and these data compared to the selectivity preference of DMT, obtained from the competition experiments, in order to assess the reasons for any discriminatory behaviour. Finally, Hirshfeld surface analysis data was used to determine if the thermal stability of the complexes was related to the number and type of interactions between host and guest.
- Full Text:
- Date Issued: 2018
- Authors: Pohl, Pieter Lourens
- Date: 2018
- Subjects: Chemistry, Organic , Clathrate compounds Thermal analysis
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23131 , vital:30432
- Description: In this study, we investigated the potential of a host compound, (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT), for use in the separation of isomers and related compounds using host-guest chemistry. The title molecule, DMT, is composed of a butane chain bearing hydroxyl moieties on the terminal carbons and methoxy moieties on the two internal, chiral carbon atoms. In addition, there are two phenyl rings on each of the terminal carbons. The synthesis of DMT was carried out by subjecting the diester of naturally-occurring optically active tartaric acid to a Grignard reaction employing phenylmagnesium bromide. Subsequent methylation of the secondary hydroxy groups with dimethyl sulfate afforded DMT. The resulting host molecule was investigated for its inclusion abilities by crystallizing with a number of potential aromatic, aliphatic and alicyclic guests such as toluene, aniline, nitrobenzene, anisole, cyclohexane, ethyl acetate and ethanol. Host:guest ratios were determined by means of 1H-NMR spectroscopy. Of the hosts investigated, DMT favoured a host:guest ratio of 2:1 for all included guests investigated. It complexed with most non-polycyclic aromatic guests as well as cyclohexane, cyclohexene and cyclohexanone. It was not able to include short chain or branched alcohols such as methanol, ethanol or 2-propanol, or other hetero-aliphatic or hetero- cyclic compounds such as diethyl ether, acetonitrile, morpholine or dioxane. Competition inclusion experiments were performed in which DMT was crystallized from equimolar and non-equimolar binary, ternary and quaternary mixtures of appropriate guests. The mother liquor mixtures and resultant crystals were subjected to GC-MS analysis in order to determine whether DMT showed discriminatory behaviour towards the guests from a mixture. It was observed that DMT was able to differentiate between related compounds, for example, the host preferred to include N,N-dimethylaniline compared with N-methylaniline and aniline. The host also discriminated against isomers, for example, p-xylene was preferentially included over o-xylene and m-xylene, while o-cresol was included in preference to p-cresol and m-cresol. Single crystal X-ray analysis was used to investigate the host–guest interactions responsible for guest inclusion, as well as to discern reasons for the host’s selective behaviour. X-ray data for the inclusion complexes indicated that each complex was isostructural, crystallizing in the monoclinic C2 crystal system. A pair of 1,3- and 2,4- intramolecular hydrogen bonds, as well as intramolecular non-classic hydrogen bonds between adjacent ortho-aromatic hydrogens and hydroxy moieties was a significant stabilizing factor for the geometry of the host. Guests were held within discrete cavities in the crystal lattice, and experienced only π–π stacking, CH–π interactions and other short contacts. Thermal analyses were used to determine the relative thermal stabilities of the complexes, and these data compared to the selectivity preference of DMT, obtained from the competition experiments, in order to assess the reasons for any discriminatory behaviour. Finally, Hirshfeld surface analysis data was used to determine if the thermal stability of the complexes was related to the number and type of interactions between host and guest.
- Full Text:
- Date Issued: 2018
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